The fragrance facts, graded

Children and pregnancy / Measured in people or real products

Three in four children's cosmetics (295 of 398, 74.1%) on sale in a Brazilian city listed "parfum/fragrance" on the label, including 90% of children's shampoos and 79% of baby wet wipes.

Moderate evidence.

Source: Uber 2024, Jornal de Pediatria (Rio de Janeiro) Link to this fact

Children and pregnancy / Measured in people or real products

Childcare air had about three times more limonene than new California homes (33 vs 11 µg/m³), which the authors link to frequent cleaning.

Moderate evidence: Comparison with a different study (Offermann 2009); daytime vs 24-h sampling.

Source: Hoang 2016, Indoor Air Link to this fact

Children and pregnancy / Measured in people or real products

Pregnant women who used lotion had 111% higher butyl paraben, a preservative that weakly mimics estrogen.

Moderate evidence: Exposure marker only.

Source: Braun 2014, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Children and pregnancy / Measured in people or real products

In a US study, baby boys whose mothers had higher levels of several phthalates in their urine during pregnancy had a shorter distance between the anus and genitals, a sign of reduced male-hormone action during development in animal studies. A much larger (N=753), purpose-designed prospective follow-up by the same research group (TIDES, Swan 2015) confirmed this specifically for DEHP metabolites (a PVC plasticizer), with a significant, dose-responsive association at about half the original exposure level. It found no association for diethyl phthalate (DEP), the phthalate used in fragrance, nor for the other three phthalates (DBP, BBzP, DiBP) that had appeared linked in the original small study.

Moderate evidence.

Source: Swan 2005, Environmental Health Perspectives Link to this fact

Children and pregnancy / Review of other studies

Synthetic musks reach mothers and babies mainly through the skin (cosmetics and clothes washed in scented detergent), not through food.

Moderate evidence.

Source: Schmeiser 2001, International Journal of Hygiene and Environmental Health Link to this fact

Children and pregnancy / Review of other studies

As of 2019, the evidence that lavender or tea tree oil causes breast growth in young children consisted only of case reports: 11 children described in detail in 4 papers, with no controlled study.

Moderate evidence: Systematic review of case reports; undercounts (one included paper reports ~20 more cases in clinic tallies).

Source: Hawkins 2020, Complementary Therapies in Medicine Industry-funded Link to this fact

Children and pregnancy / Animal study

In the only independent animal experiment on the question, female rats housed with a lavender-oil diffuser from weaning reached puberty about 4.6 days earlier than unexposed rats (33.8 vs 38.4 days), with luteinizing hormone about 35% higher and follicle-stimulating hormone about 45% higher and no difference in body weight.

Moderate evidence: Five rats per group, one species, one sex, a single dose that was never measured in the cage air; no human data. The paper's abstract mislabels which group was exposed how.

Source: Kim & Lim 2022, Journal of Korean Medical Science Link to this fact

Children and pregnancy / Animal study

The effect appeared through breathing the air rather than through skin contact, which matters because the main scientific defense of lavender products is that too little gets through the skin to do anything.

Moderate evidence: Rat study; the inhaled dose was not measured, and no one has measured what a real room diffuser puts into the air either.

Source: Kim & Lim 2022, Journal of Korean Medical Science Link to this fact

Children and pregnancy / Animal study

In the same industry study's one-generation rat screen, the highest linalool dose (800 mg/kg/day, high enough to make the mother rats visibly ill) produced more stillbirths, worse pup survival in the first four days and pups that stayed smaller throughout nursing; the authors call follow-up testing 'mandatory' before this can be dismissed.

Moderate evidence.

Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact

Children and pregnancy / Measured in people or real products

In a Danish/multi-country test of 25 children's cosmetics and cosmetic-toys, all 7 hydro-alcoholic children's fragrance products (5 eau de toilette, 1 eau de parfum, 1 roll-on deodorant) contained the allergen geraniol, and a separate children's toy-cosmetic perfume-blending kit's lilac essence contained cinnamic alcohol at 3.7% — about 4.6x (the paper's abstract states "by a factor of 5") the IFRA guideline of 0.8%.

Moderate evidence.

Source: Pastor-Nieto 2021 (Rastogi 1999), Current Treatment Options in Allergy Link to this fact

Children and pregnancy / Animal study

When rats were fed the sunscreen ingredient 4-MBC from before conception through pregnancy and nursing, male offspring reached puberty later and had smaller prostates as adults; the lowest dose that did this was 7 mg/kg/day, and for the related compound 3-BC it was 0.24 mg/kg/day, the lowest dose tested.

Moderate evidence.

Source: Schlumpf 2004, Toxicology Link to this fact

Children and pregnancy / Animal study

Developmental exposure to 4-MBC changed the activity of estrogen-controlled genes in the adult offspring's uterus, prostate, and hypothalamus, erased the normal male-female difference in hypothalamic progesterone-receptor mRNA, and changed how those tissues later responded to an estrogen challenge.

Moderate evidence.

Source: Schlumpf 2004, Toxicology Link to this fact

Children and pregnancy / Self-reported survey

In a Brazilian hospital survey, caregivers said two in three children aged 14 and under (182 of 276, median age 4) wore perfume.

Moderate evidence: One Curitiba tertiary-hospital clinic sample, 2015-16; 'perfume' undefined; no frequency, age, or sex breakdown; count identical to children's shampoo (possible copy error).

Source: Melo 2020, Revista Paulista de Pediatria Link to this fact

Children and pregnancy / Self-reported survey

A quarter of Brazilian children in a hospital survey (71 of 276) already wore make-up, starting at a median age of 4, usually because the child asked for it (75% of users).

Moderate evidence: One hospital sample; caregiver report; frequency not asked.

Source: Melo 2020, Revista Paulista de Pediatria Link to this fact

Children and pregnancy / Measured in people or real products

In a Danish registry of 1,179 cosmetics marketed for children, more than half (634, 53.8%) listed perfume or a named fragrance allergen, and nearly half (550, 46.6%) named at least one of the 26 EU-listed fragrance allergens.

Moderate evidence.

Source: Botvid 2023, Contact Dermatitis Link to this fact

Children and pregnancy / Measured in people or real products

93% of children's facial-care products in a Danish registry (80 of 86, almost all lip balms) listed fragrance, averaging nearly two named fragrance allergens each.

Moderate evidence: Label data; n=86; registry sample.

Source: Botvid 2023, Contact Dermatitis Link to this fact

Children and pregnancy / Review of other studies

Balsam of Peru, a strong skin sensitizer that the fragrance industry's own standards body (IFRA) had recommended banning, was an ingredient of popular US diaper-rash ointments in the 1990s, applied under occlusion to inflamed infant skin.

Moderate evidence: One clinical commentary citing one 1990 case series (Fisher); current diaper-rash product formulations were not checked for this page.

Source: Scheinman 1999, Journal of the American Academy of Dermatology Link to this fact

Children and pregnancy / Measured in people or real products

In a US label survey of 533 personal care products marketed for babies and children, 48% (255/533) contained a fragrance-category allergen and 55% (294/533) contained at least one of eight screened contact allergens.

Moderate evidence.

Source: Bonchak 2018, Dermatitis Link to this fact

Children and pregnancy / Measured in people or real products

Cheaper baby and children's personal care products contain significantly more contact allergens than pricier ones: products with two or more screened allergens averaged $1.39 per ounce versus $4.35 per ounce for products with none.

Moderate evidence.

Source: Bonchak 2018, Dermatitis Link to this fact

Children and pregnancy / Measured in people or real products

Pregnant women who used perfume in a 48-hour window had 2.3 times higher urinary levels of MEP, the breakdown product of the fragrance solvent diethyl phthalate (DEP), than non-users, in a study of 186 low-income African American and Dominican pregnant women in New York City — independently replicating the same finding in a Boston fertility-clinic cohort (Braun 2014, 167% higher) and a postpartum cohort (Parlett 2013, 2.92x).

Moderate evidence: Exposure marker only, no health outcome; single cohort, cross-sectional; 95% CI 1.6-3.3 overlaps Braun 2014 and Parlett 2013.

Source: Just 2010, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Children and pregnancy / Measured in people or real products

More frequent perfume use tracked higher urinary MEP in pregnant women in a clear dose-response pattern.

Moderate evidence: N=128 subset; exposure marker only, no health outcome.

Source: Just 2010, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Children and pregnancy / Measured in people or real products

In an ordinary primary-school classroom, children were exposed to ultrafine-particle bursts reaching 140,000 particles per cubic centimeter during art activities, the highest classroom particle level measured among the wiki's school-exposure studies — with no health outcome measured.

Moderate evidence.

Source: Morawska 2009, Environmental Science & Technology Link to this fact

Children and pregnancy / Measured in people or real products

In a 1999 European lab test, all 7 children's hydro-alcoholic fragrance products (eau de toilette, eau de parfum, roll-on deodorant) contained the allergen geraniol, and a children's toy perfume-blending kit's "lilac essence" contained cinnamic alcohol at 3.7% — about 4.6x (the paper's abstract states "by a factor of 5") the industry's own 0.8% safety guideline.

Moderate evidence.

Source: Rastogi 1999, Contact Dermatitis Link to this fact

Children and pregnancy / Measured in people or real products

Everyday children's shampoos, shower gels, creams, and lotions rarely contained fragrance-mix allergens — cinnamic alcohol, cinnamic aldehyde, and isoeugenol were absent from every sample tested — while the notable allergen exposure was concentrated in perfume-type products and one toy.

Moderate evidence: N=5 shampoos/shower gels, n=4 creams/lotions; small sample.

Source: Rastogi 1999, Contact Dermatitis Link to this fact

Children and pregnancy / Measured in people or real products

In a small pilot study of 14 Washington DC childcare facilities, chloroform – a byproduct of the chlorine bleach used to clean – was found in every single air sample, at levels averaging 1.4-1.8 times higher than in a comparable California childcare study.

Moderate evidence: Small unfunded pilot (14 facilities), single-day snapshot, convenience sample; measured no fragrance chemicals at all.

Source: Quirós-Alcalá 2016, Environmental Research Link to this fact

Children and pregnancy / Measured in people or real products

Two no-lye hair relaxer kits marketed for children had the highest measured levels of chemicals banned in EU cosmetics or listed under California's Proposition 65 (DEHP, nonylphenol, o-phenylphenol, diethanolamine) of any products tested in this study.

Moderate evidence: N=3 relaxer kits (2 marketed for children); no health outcome measured in children who used these products.

Source: Helm 2018, Environmental Research Link to this fact

Children and pregnancy / Measured in people or real products

In a Czech birth cohort of 3,411 children (ELSPAC-CZ), each 1-SD increase in an 18-product household chemical exposure score measured at 6 months raised the odds of intermediate-onset transient wheeze (adjusted OR 1.27), early-onset persistent wheeze (adjusted OR 1.36) and intermediate-onset persistent wheeze (adjusted OR 1.23) through age 5, and those persistent wheeze phenotypes carried 5-8x higher odds of a doctor-diagnosed asthma by age 7 (pediatrician records, not self-report).

Moderate evidence.

Source: Mikeš 2019, Science of the Total Environment Link to this fact

Children and pregnancy / Self-reported survey

Mothers who use cleaning sprays during pregnancy have infants with higher odds of both a lower respiratory tract infection (29% higher, OR 1.29) and wheezing (37% higher, OR 1.37) in their first year of life, in a pooled analysis of four Spanish birth cohorts (n=2,292); prenatal solvent use also raised wheezing odds (30% higher) and prenatal air freshener use raised LRTI odds (29% higher).

Moderate evidence.

Source: Casas 2013, International Journal of Public Health Industry-funded Link to this fact

Children and pregnancy / Self-reported survey

In a random sample of Swedish teenagers aged 13-19, about 1 in 6 (15.6%) said they were bothered by strong odors such as perfume, cleaning agents, or flower scents, most often affecting the nose.

Moderate evidence: Single-item self-report; general odor sensitivity, not fragranced-product-specific; one Swedish town.

Source: Andersson 2008, International Journal of Hygiene and Environmental Health Link to this fact

Children and pregnancy / Self-reported survey

Teenage girls reported chemical sensitivity about twice as often as boys (20.6% vs 9.9%), and being female, being sensitive to noise, or having probable anxiety each roughly doubled the odds of reporting it.

Moderate evidence: Logistic regression with low explanatory power (Nagelkerke R2=0.092); only modeled for the general-CS outcome.

Source: Andersson 2008, International Journal of Hygiene and Environmental Health Link to this fact

Children and pregnancy / Measured in people or real products

In a US EPA/CDC study of 33 breastfeeding women, phthalate breakdown products were detected in fewer than 10% of breast milk samples and were essentially absent from saliva, even though the same women had detectable phthalate metabolites in nearly all of their urine samples.

Moderate evidence.

Source: Hines 2009, Environmental Health Perspectives Link to this fact

Children and pregnancy / Measured in people or real products

In a large US study of 753 pregnant women and their newborns, higher first-trimester urinary levels of DEHP (a plasticizer found in PVC, food packaging, and some medical devices, not primarily a fragrance ingredient) were associated with a shorter anogenital distance in baby boys, a sign of reduced male-hormone action during development, replicating an earlier smaller study at about half the exposure level.

Moderate evidence.

Source: Swan 2015, Human Reproduction Link to this fact

Children and pregnancy / Measured in people or real products

In the same large study (N=753), urinary levels of diethyl phthalate (DEP), the phthalate most strongly and consistently tied to perfume and fragranced personal-care product use, showed no association with anogenital distance in baby boys — the largest and best-controlled human test yet of this specific fragrance-phthalate reproductive claim, in the same boys where DEHP did show an effect.

Moderate evidence.

Source: Swan 2015, Human Reproduction Link to this fact

Children and pregnancy / Review of other studies

The developing fetal and infant brain is far more vulnerable to industrial-chemical injury than the adult brain: the placenta is not an effective barrier to most industrial chemicals, the blood-brain barrier is not fully formed until about 6 months after birth, and lipophilic persistent chemicals concentrate in breast milk at up to 100-fold the mother's bodyweight-adjusted exposure.

Moderate evidence.

Source: Grandjean & Landrigan 2006, Lancet Link to this fact

Children and pregnancy / Measured in people or real products

In 101 Swedish first-time mothers tested over seven years, women who used perfume once a week or more had significantly higher levels of the musk chemical galaxolide (HHCB) in their breast milk than women who used it less often.

Moderate evidence: Product-use data from a N=44 subset; cross-sectional association, not an intervention; adjusted for sampling year.

Source: Lignell 2008, Environmental Science & Technology Link to this fact

Children and pregnancy / Measured in people or real products

Mothers who used perfumed laundry detergent had significantly higher levels of the musk chemical tonalide (AHTN) in their breast milk than mothers who used unscented detergent.

Moderate evidence: Product-use data from a N=44 subset; cross-sectional association, not an intervention; adjusted for sampling year.

Source: Lignell 2008, Environmental Science & Technology Link to this fact

Children and pregnancy / Measured in people or real products

In a national Canadian survey of 98 baby care products, diaper cream — not fragrance — was the largest single modeled source of infant dermal DEP exposure, contributing about half of babies' modeled total.

Moderate evidence: Exposure model uses non-Canada-specific consumer-use-pattern data and a fixed 5% skin-absorption assumption for all phthalates; it is a modeled dose, not a measured biomarker.

Source: Koniecki 2011, Environmental Research Link to this fact

Children and pregnancy / Other evidence

In 1998, EPA's own pesticide-program administrator reported that, per an outside audit of a random 100-chemical sample, 71% of the roughly 3,000 highest-volume industrial chemicals in US commerce had no basic toxicity data publicly available at all, and 63% had not been tested for carcinogenicity.

Moderate evidence.

Source: Goldman 1998, Environmental Health Perspectives Link to this fact

Children and pregnancy / Self-reported survey

In a 170-home substudy of the UK ALSPAC birth cohort, mothers who used air fresheners daily or on most days during pregnancy were more likely to later report their infant had diarrhea (adjusted OR 1.10) or earache (adjusted OR 1.30, with a dose-response across use frequency) in the first 6 months of life than mothers who rarely used them.

Moderate evidence.

Source: Farrow 2003, Archives of Environmental Health: An International Journal Link to this fact

Children and pregnancy / Self-reported survey

In the same ALSPAC substudy, mothers who used 'other' aerosols or sprays daily or on most days during pregnancy were more likely to report their infant had diarrhea (adjusted OR 1.22) or vomiting (adjusted OR 1.14) in the first 6 months of life than mothers who rarely used them.

Moderate evidence.

Source: Farrow 2003, Archives of Environmental Health: An International Journal Link to this fact

Children and pregnancy / Self-reported survey

In a large UK birth cohort (ALSPAC, n=7,019), each 1-unit increase in a composite score of prenatal household chemical product use (11 products, frequency-weighted) raised the odds of persistent wheeze through age 3.5 by 6% (adjusted OR 1.06, 95% CI 1.03-1.09), and children of mothers in the top decile of use were more than twice as likely to wheeze persistently as those in the bottom decile (adjusted OR 2.3, 95% CI 1.2-4.4); transient early wheeze and late onset wheeze showed no significant adjusted association.

Moderate evidence.

Source: Sherriff et al. 2005, Thorax Link to this fact

Children and pregnancy / Measured in people or real products

In a Belgian study of 234 schoolchildren aged 10-13, those living in homes cleaned with chlorine bleach at least once a week had a much lower rate of doctor-diagnosed or test-confirmed asthma than other children (3.8% vs 13.5%; adjusted odds ratio 0.10, 95% CI 0.02-0.51).

Moderate evidence.

Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact

Children and pregnancy / Measured in people or real products

In the same study, children in bleach-cleaned homes were also less likely to have doctor-diagnosed eczema (3.8% vs 14.1%, adjusted OR 0.22) and to be sensitized to indoor aeroallergens, especially house dust mite (adjusted OR 0.53 and 0.43 respectively), but showed no difference in sensitization to pollen allergens.

Moderate evidence.

Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact

Children and pregnancy / Measured in people or real products

The protective association between bleach cleaning and reduced allergy/asthma risk was abolished in households with parental smoking; in that subgroup, bleach use was instead linked to a higher rate of recurrent bronchitis (adjusted OR for the smoking-by-bleach interaction, 2.03, 95% CI 1.12-3.66).

Moderate evidence: Subgroup/interaction analysis from a single cross-sectional study; the recurrent-bronchitis outcome is parent-reported, not medically confirmed.

Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact

Children and pregnancy / Self-reported survey

In a 300-woman New York City pilot study, women who recalled childhood hair oil use (before age 13) were about 40% more likely to report an earlier first period (before age 12) than non-users, after adjusting for race/ethnicity and birth decade (adjusted risk ratio 1.4, 95% CI 1.1-1.9).

Moderate evidence.

Source: James-Todd 2011, Annals of Epidemiology Link to this fact

Children and pregnancy / Self-reported survey

Childhood hair perm/relaxer use was also linked to an earlier first period (adjusted risk ratio 1.4, 95% CI 1.1-1.8) in this study, but hair lotion, leave-in conditioner, and home-style products like vitamin or vegetable oils were not.

Moderate evidence: Cross-sectional, retrospective recall; only 50 women in the sample reported ever using hair perms/relaxers.

Source: James-Todd 2011, Annals of Epidemiology Link to this fact

Children and pregnancy / Self-reported survey

Girls who started using hair oil at least two years before their first period had a stronger link to earlier menarche (adjusted risk ratio 1.8, 95% CI 1.2-3.0), and the link was strongest for reaching menarche by age 11 specifically (adjusted risk ratio 5.3, 95% CI 1.5-19.1).

Moderate evidence: Based on a small subgroup (n=84 extended users); the wide confidence interval on the age-11 estimate reflects very few events; single small pilot study.

Source: James-Todd 2011, Annals of Epidemiology Link to this fact

Children and pregnancy / Self-reported survey

Black women recalled far more childhood hair oil use than Hispanic or white women (94% of African-American and 74% of African-Caribbean women, vs. 33% of Hispanic and 9% of white women) in this New York City sample.

Moderate evidence: Self-reported recall in a convenience sample from one city (New York, 2004-2005); does not measure the chemical content of the products used.

Source: James-Todd 2011, Annals of Epidemiology Link to this fact

Children and pregnancy / Self-reported survey

In a pooled study of 248 women in two New York cohorts, childhood use (before age 13) of any hair product was associated with roughly double the risk of reaching menarche before age 11 (RR 2.3, 95% CI 1.1-4.8), but the association weakened to non-significance after also adjusting for race/ethnicity (RR 1.8, 95% CI 0.8-4.1).

Moderate evidence.

Source: McDonald 2018, Environmental Health Link to this fact

Children and pregnancy / Self-reported survey

Childhood hair oil use specifically was associated with earlier menarche (RR 2.5, 95% CI 1.2-5.2 before race adjustment; RR 2.3, 95% CI 1.0-5.5 after), the same direction as an earlier pilot study by the same senior author.

Moderate evidence.

Source: McDonald 2018, Environmental Health Link to this fact

Children and pregnancy / Self-reported survey

Essentially no non-Hispanic white women in this New York sample reported using hair products before age 11, versus substantial use among Hispanic and non-Hispanic black participants who reached early menarche.

Moderate evidence: Based on a very small subgroup (26 of 248 women reached menarche before 11); reflects this specific sample and era (data collected 2001-2008), not a national or current estimate.

Source: McDonald 2018, Environmental Health Link to this fact

Children and pregnancy / Self-reported survey

In a Dutch birth cohort of 2,333 adolescents (age 14), a composite score for household use of 10 types of cleaning agents was not associated with asthma, rhinitis, or eczema, even at the highest exposure quartile: adjusted OR (95% CI) 0.95 (0.56, 1.63) for asthma, 1.23 (0.83, 1.82) for rhinitis, and 0.95 (0.56, 1.63) for eczema, comparing highest to never/seldom use.

Moderate evidence.

Source: Bukalasa et al. 2019, Environment International Link to this fact

Children and pregnancy / Self-reported survey

A sensitivity analysis restricted to the 988 adolescents (42% of the cohort) reported to be sometimes or mostly present at home during cleaning activities again found no association between the composite cleaning-agent-use score and asthma, rhinitis, or eczema, confirming the main null result.

Moderate evidence.

Source: Bukalasa et al. 2019, Environment International Link to this fact

Children and pregnancy / Measured in people or real products

The limonene-asthma association was substantially stronger in children than adults in this Canadian national survey: children (6-16y) had an adjusted odds ratio of 1.46 (95% CI 1.45-1.47) for asthma per 100% increase in indoor limonene versus 1.16 (95% CI 1.15-1.16) in adults (17-79y), and the FeNO increase was about twice as large in children (2.89%, 95% CI 1.88-4.43) as in adults (1.44%, 95% CI 1.16-1.79).

Moderate evidence.

Source: Dales & Cakmak 2019, Environmental Pollution Industry-funded Link to this fact

Children and pregnancy / Measured in people or real products

Laundry detergents marketed 'baby safe' (n=5) were fragranced in 80% of products (4 of 5) and had the highest average common-allergen count of any detergent subgroup studied (2.6 allergens/product), higher than plain scented-liquid detergents (2.4/product).

Moderate evidence: Small subgroup, n=5; ingredient-label survey, not a measured exposure or clinical outcome.

Source: Bai 2020, Dermatitis® Link to this fact

Children and pregnancy / Other evidence

No controlled human exposure studies investigating whether children, elderly people, or smokers are more sensitive to irritant chemicals than healthy young adults could be found in the literature through August 2020.

Moderate evidence: Absence of studies, not evidence of no difference; the same evidence gap for children is documented in more detail by a later 2024 review.

Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact

Children and pregnancy / Other evidence

In a retrospective cohort of 266 pediatric ICU admissions treated with continuous nebulized albuterol, benzalkonium-chloride-containing albuterol was not associated with worse PICU or hospital length of stay, need for adjunctive respiratory support, or mortality than preservative-free albuterol — if anything, length of stay was shorter in the benzalkonium-chloride group.

Moderate evidence.

Source: Al-Subu et al. 2023, Respir Care 68(6):734-739, Respiratory Care Link to this fact

Children and pregnancy / Other evidence

Children who received benzalkonium-chloride-containing continuous nebulized albuterol in this cohort were started on a significantly higher initial albuterol dose (median 15, later 20 mg/h in the critical-asthma sub-analysis) than children who received preservative-free albuterol (median 10-15 mg/h), a difference that persisted even after restricting to a diagnostically matched critical-asthma sub-group.

Moderate evidence.

Source: Al-Subu et al. 2023, Respir Care 68(6):734-739, Respiratory Care Link to this fact

Children and pregnancy / Other evidence

When the comparison was restricted to children over age 2 with a critical-asthma diagnosis specifically (n=160), there was no significant difference between the benzalkonium-chloride and preservative-free albuterol groups in PICU length of stay, hospital length of stay, or any secondary outcome except the (still higher) initial albuterol dose.

Moderate evidence.

Source: Al-Subu et al. 2023, Respir Care 68(6):734-739, Respiratory Care Link to this fact

Children and pregnancy / Measured in people or real products

A deodorant vapo-spray labeled "perfume for babies" in this 1996 European sample contained 14 of 21 tested fragrance substances at levels up to 1640 ppm, including 4 fragrance-mix allergens.

Moderate evidence.

Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact

Children and pregnancy / Other evidence

Fragrance contact allergy is not rare in children: in a study of 1200 Danish school children aged 12-16, 1.6% of girls and 2.1% of boys tested positive to the fragrance mix, and one in three of them already had clinical symptoms.

Moderate evidence: Single study (secondary citation); the primary (Mortz 2002) is not yet in our evidence base.

Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact

Children and pregnancy / Review of other studies

Children have required hospitalization for severe allergic reactions to hair dyes (paraphenylenediamine).

Moderate evidence: Relayed from a single case series (Sosted et al. 2006, 8 children).

Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact

Children and pregnancy / Review of other studies

Newborn infants placed on the mother's stomach spontaneously crawl toward the breast guided by smell (and do not do so if the areolas are washed), and even formula-fed infants prefer the odor of a lactating breast, suggesting the preference is innate rather than learned.

Moderate evidence: Small experimental studies from the 1990s cited secondhand; not this review's own data.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Children and pregnancy / Measured in people or real products

Only 49 of 230 baby-specific cosmetic products (21.3%) registered through a Danish consumer app in 2015-16 were labeled to contain fragrance, the lowest fragranced rate of the 15 product categories studied; most of the fragranced ones (41 of 49) were leave-on products (creams, lotions, oils, wet wipes).

Moderate evidence.

Source: Bennike 2017/2018 Link to this fact

Children and pregnancy / Review of other studies

This report names pregnant and breastfeeding women, young children, teenagers, and cancer patients on anti-cancer treatment as groups who should be protected from continuous EDC exposure, because EDCs can cross the placenta and pass into breast milk.

Moderate evidence: No perfume-specific dose or exposure data for these populations is given.

Source: Tegengif 2022 Link to this fact

Children and pregnancy / Measured in people or real products

In FDA's 2010 follow-up survey, 5 of 24 baby-care products (shampoos, body washes, creams, lotions, and oils) contained diethyl phthalate (DEP), at levels up to 274 ug/g — the only phthalate ester found in any baby-care product tested.

Moderate evidence: N=24 baby-care products from one FDA survey; no infant absorbed-dose or health-outcome data were collected.

Source: Hubinger 2010, Journal of Cosmetic Science Link to this fact

Children and pregnancy / Government agency

Exposure to hormone-disrupting chemicals during fetal development, infancy, and puberty can permanently reprogram how tissues develop, with effects that may not become visible until years or decades later; children are considered the most vulnerable population because of their hand-to-mouth behavior and higher metabolic rate.

Moderate evidence: This is the report's general developmental-programming framework, illustrated mainly with lead, PCBs, DES, and pesticides, not with fragrance chemicals.

Source: WHO/UNEP 2012 Link to this fact

Children and pregnancy / Government agency

The European Commission's 2018 endocrine disruptor framework names fetal development and puberty as the exposure periods of greatest concern, stating that exposure during these windows may cause permanent effects and raise disease susceptibility later in life.

Moderate evidence.

Source: EU Commission 2018 Link to this fact

Children and pregnancy / Animal study

In mice, a single prenatal dose of the plasticizer DEHP to a pregnant female can alter reproductive traits (puberty timing, ovarian follicle numbers, fertility, reproductive aging) not just in her directly exposed pups, but in her never-exposed great-grandpups (the F3 generation), an effect attributed to epigenetic changes carried through the germline.

Moderate evidence.

Source: Brehm & Flaws 2019, Endocrinology Link to this fact

Children and pregnancy / Animal study

Diethyl phthalate (DEP), the phthalate used as a fragrance solvent and fixative in colognes, perfumes, and nail polish, has never been tested alone for transgenerational (multi-generation) reproductive effects; the only relevant animal study exposed pregnant mice to a five-phthalate mixture that was 35% DEP, and could not separate DEP's contribution from the other four phthalates.

Moderate evidence.

Source: Brehm & Flaws 2019, Endocrinology Link to this fact

Children and pregnancy / Review of other studies

Higher urinary BPA is linked to childhood and adolescent obesity in several large NHANES-based US studies; in one, children in the highest quarter of urinary BPA had more than double the odds of obesity of children in the lowest quarter.

Moderate evidence.

Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact

Children and pregnancy / Review of other studies

Before the 2010s, essentially every cosmetic-safety exposure estimate for adults rested on just two large industry-run studies — one European, one American — and there was no published consumption or exposure data at all for babies, children, adolescents, or pregnant women; that gap only started closing in the last decade.

Moderate evidence: A single review's characterization of the literature, not a primary measurement; two of its four authors work for a cosmetics manufacturer (Pierre Fabre).

Source: Ficheux 2019, systematic review of 82 studies, 2000-Feb 2018, Food and Chemical Toxicology Industry-funded Link to this fact

Children and pregnancy / Review of other studies

The Endocrine Society's 2025 position statement calls for EDC regulations to be designed to protect the most vulnerable populations, explicitly naming fetuses, children, pregnant women, and adolescents, because critical developmental windows such as fetal development and infancy affect vulnerability to EDC effects on later-life outcomes.

Moderate evidence: A general policy recommendation across all EDC-containing product categories, not specific to cosmetics or fragrance exposure.

Source: Endocrine Society 2025 Link to this fact

Children and pregnancy / Review of other studies

Human cohort studies summarized in a 2017 review link prenatal and childhood phthalate exposure to poorer childhood executive function, attention, aggression, depression, and ADHD diagnosis/severity.

Moderate evidence.

Source: Kanwal 2017 review, citing Engel 2010, Cho 2010, Kim 2009, Park 2015, Environmental Research Link to this fact

Children and pregnancy / Review of other studies

Phthalates such as DEHP are not chemically bound to PVC medical devices, so they continuously leach out of them; the US FDA issued a public health warning about DEHP in medical devices in 2001, and NICU neonates can receive DEHP exposure up to 20 times the tolerable daily intake from medical devices.

Moderate evidence.

Source: Latini/Italian review 2006, Toxicology Link to this fact

Children and pregnancy / Measured in people or real products

In a US cohort, phthalates measured in mothers' urine during pregnancy were associated with poorer executive function and more aggressive and depressive-type behavior in their children ages 4-9 (Engel 2010).

Moderate evidence.

Source: Engel 2010, cited in Kanwal 2017 review, Environmental Research Link to this fact

Fragrance is everywhere / Measured in people or real products

Perfume, air fresheners, and dryer sheets carried the highest levels of fragrance chemicals and the phthalate DEP; the pooled perfume sample was 1.4% DEP by weight.

Moderate evidence.

Source: Dodson 2012, Environmental Health Perspectives Link to this fact

Fragrance is everywhere / Measured in people or real products

A lab analysis of 59 soaps, surface cleaners, laundry and dish-washing products from four European countries found the citrus-scent chemical limonene in 78% of them, linalool in 61%, and citronellol in 47%; all three are fragrance chemicals linked to skin allergy.

Moderate evidence: Products c. 2000, EU only; parent terpenes measured, not the allergenic oxidized forms; Unilever co-author.

Source: Rastogi 2001, Contact Dermatitis Industry-funded Link to this fact

Fragrance is everywhere / Measured in people or real products

Women who had used perfume in the previous day had nearly 3 times as much of a phthalate breakdown product (from diethyl phthalate, a chemical used to carry fragrance) in their urine as women who hadn't.

Moderate evidence: Single spot urine, 337 mostly white educated women; replicated by Braun 2014.

Source: Parlett 2013, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Fragrance is everywhere / Measured in people or real products

The more personal care products a woman used, the higher her levels of diethyl phthalate; deodorant (2.8x), nail polish (2.1x) and hair spray (1.8x) users also had higher levels.

Moderate evidence: Cross-sectional association; one urine sample.

Source: Parlett 2013, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Fragrance is everywhere / Self-reported survey

99.1% of US adults said they are exposed to fragranced products at least once a week, from their own use, other people's, or both.

Moderate evidence: Self-reported exposure; weak dose proxy; adults 18-65.

Source: Steinemann 2016, Air Quality, Atmosphere & Health Link to this fact

Fragrance is everywhere / Review of other studies

In California's 1997 inventory, air fresheners were the single largest category of cleaning-product chemical emissions: 7.5 metric tons a day, just ahead of general-purpose cleaners.

Moderate evidence: 1997 sales-based inventory; later SoCAB inventory had air fresheners <2.5 t/d.

Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact

Fragrance is everywhere / Review of other studies

Of 83 chemicals the EPA had flagged as priorities for safety review (TSCA Work Plan), 65 (over 80%) were known to be in consumer products.

Moderate evidence: Not fragrance-specific.

Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact

Fragrance is everywhere / Self-reported survey

99.3% of UK adults are exposed to fragranced products every week, and 89% through other people's products that they did not choose.

Moderate evidence: Self-reported exposure.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Fragrance is everywhere / Measured in people or real products

The more personal care products a pregnant woman used in a day, the higher her urine levels of phthalates and parabens, rising step by step.

Moderate evidence: Association with self-reported use.

Source: Braun 2014, Journal of Exposure Science and Environmental Epidemiology Link to this fact

Fragrance is everywhere / Review of other studies

In US national biomonitoring, MEP, the breakdown product of the fragrance solvent DEP, was the most abundant phthalate in people's urine (average 181 ug/g creatinine).

Moderate evidence: NHANES data cited by a review; cite CDC primary; secondary citation of older NHANES data, cite the CDC report directly.

Source: Crinnion 2010, Alternative Medicine Review Link to this fact

Fragrance is everywhere / Measured in people or real products

In a test of 59 best-selling Korean household products, the citrus-scent chemical limonene was the chemical most often given off: it came from 44% of products, including bleach, dish soap, laundry detergent, disinfectant, and even a liquid pesticide.

Moderate evidence: Heated headspace, library-match ID, presence not exposure.

Source: Kwon 2007, Journal of Hazardous Materials Link to this fact

Fragrance is everywhere / Review of other studies

In the Los Angeles air basin in 2005, consumer products such as hair spray, cleaners, and perfumes were the second-largest human-made source of organic gases by weight (118.7 metric tons a day), behind only passenger cars, according to California's air regulator.

Moderate evidence.

Source: Chen & Luo 2012, Atmospheric Environment Link to this fact

Fragrance is everywhere / Review of other studies

Even after accounting for how readily each chemical forms smog, consumer products ranked third among all emission sources in the Los Angeles basin in 2005.

Moderate evidence.

Source: Chen & Luo 2012, Atmospheric Environment Link to this fact

Fragrance is everywhere / Review of other studies

Perfumes and colognes alone released about 2.5 metric tons of organic gases a day into Los Angeles air in 2005, not counting fragrance in cleaners, air fresheners, or hair spray.

Moderate evidence: Inventory estimate for one CARB category.

Source: Chen & Luo 2012, Atmospheric Environment Link to this fact

Fragrance is everywhere / Measured in people or real products

In an EPA survey of 1,159 US household products from the late 1980s (mostly paints, automotive products, lubricants, and cleaners), 81% contained at least one of 31 common solvents at more than 0.1% of the product's weight, often at tens of per cent.

Moderate evidence: Historical (1987 purchases), solvent-biased sample, not fragranced products; composition not air levels.

Source: Sack 1992, Atmospheric Environment. Part A. General Topics Link to this fact

Fragrance is everywhere / Measured in people or real products

Household products have been recognized as a major source of indoor chemical pollution since at least the 1980s; this EPA survey was one of the first to measure it.

Moderate evidence: Product content, not exposure.

Source: Sack 1992, Atmospheric Environment. Part A. General Topics Link to this fact

Fragrance is everywhere / Measured in people or real products

Unlike traffic chemicals, scent chemicals were just as high in northern as in southern Europe (median 11.4 vs 12.0 ug/m3), pointing to everyday product use across the continent.

Moderate evidence: Grouped terpenes, no significance tests.

Source: Geiss 2011, Atmospheric Environment Link to this fact

Fragrance is everywhere / Measured in people or real products

In a lab experiment, women still learned to react differently to two women's body odors when both wore the same perfume: perfume did not stop people telling individuals apart by smell.

Moderate evidence.

Source: Gaby & Dalton 2019, Perception Link to this fact

Fragrance is everywhere / Review of other studies

Musk ketone, a synthetic musk used mainly in cosmetics, was found in the body fat of every German tested in the 1990s and in breast milk at up to 240 µg per kg of milk fat.

Moderate evidence.

Source: Schmeiser 2001, International Journal of Hygiene and Environmental Health Link to this fact

Fragrance is everywhere / Measured in people or real products

An older nitro musk (musk ketone), after European industry had moved away from nitro musks, was still in 85% of US mothers' milk in 2004.

Moderate evidence: N=39, Massachusetts only.

Source: Reiner 2007, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Animal study

The vapor from a single cologne contained at least twenty identifiable chemicals – limonene, linalool, linalyl acetate, alpha- and beta-pinene, terpinolene, citronellol, anethole, coumarin, diethyl phthalate among them – none of which appear on the label.

Moderate evidence: Qualitative GC/MS of one test atmosphere, recoveries unknown, isomers possibly unresolved; one unnamed product.

Source: Anderson & Anderson 1998, Archives of Environmental Health Link to this fact

Fragrance is everywhere / Review of other studies

Fragrance is not only in perfume: dermatologists list it in makeup, shampoo, sunscreen, toothpaste, mouthwash, wipes, dish soap, detergent, air fresheners, cleaners, plastics, rubber, glue, paint, and waxes, and one Belgian survey found fragrance in 10% of topical medicines (66 different fragrance substances).

Moderate evidence: Qualitative list (de Groot 2020); the 10% is Nardelli 2009, Belgium.

Source: Rodriguez 2024, Cutis Link to this fact

Fragrance is everywhere / Self-reported survey

In a New Jersey university community, adults had used an average of about 14 personal care products in the previous day or two.

Moderate evidence: 593 highly educated, 86% female university-affiliated adults, 2019; not nationally representative.

Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact

Fragrance is everywhere / Measured in people or real products

All five scented personal-care products tested, including a hand lotion and a roll-on deodorant, released terpene fragrance chemicals that react with ozone in indoor air.

Moderate evidence: 5 Swiss grocery-store products; lotion/roll-on emissions measured from a Kimwipe for 1 h, not skin.

Source: Wu 2024, Environmental Science & Technology Letters Link to this fact

Fragrance is everywhere / Measured in people or real products

All 31 UK shampoos, shower gels, conditioners, moisturizers, and foundations with reported emission rates gave off fragrance terpenes (measured together as limonene); shampoos and shower gels released the most.

Moderate evidence.

Source: Yeoman 2020, Indoor Air Link to this fact

Fragrance is everywhere / Review of other studies

About 60% of the fragrance used in homes goes down the drain into rivers and lakes, and wastewater treatment removes little of it; polycyclic musks such as galaxolide turn up in rivers, lake air, mussels, and human milk.

Moderate evidence.

Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact

Fragrance is everywhere / Review of other studies

PTFE, the non-stick coating better known as Teflon, is used in foundations, mascara, and lipsticks as a filler and slip agent, at up to 13% of leave-on products according to the industry-funded Cosmetic Ingredient Review.

Moderate evidence: Use level is a maximum reported by industry, not a typical level; industry-author review in a new non-indexed journal.

Source: Jomaa 2024, Journal of the Netherlands Society of Toxicology (JNST) Industry-funded Link to this fact

Fragrance is everywhere / Review of other studies

A 1991 US EPA survey of 31 fragrance products already found limonene, linalool, alpha-pinene, benzyl acetate, benzyl alcohol, camphor, and acetone among the most common chemicals, the same compounds found in fragranced products tested in the 2010s.

Moderate evidence: Known only second-hand (Kendall 1995 list; Steinemann 2011 quotes its prevalences); the EPA report itself is not in our evidence base.

Source: DONTSPRAYCALIFORNIA 2008 (DOJ ADA docket) Link to this fact

Fragrance is everywhere / Measured in people or real products

Plug-in and hanging car air fresheners mainly release fragrance terpenes (limonene, pinene, dihydromyrcenol) and fruity-smelling esters, the same terpenes found across larger product surveys.

Moderate evidence.

Source: Pino-Delgado 2021; Steinemann 2011, Journal of Student Research Link to this fact

Fragrance is everywhere / Animal study

The sunscreen ingredient 4-MBC built up in the rats' body fat: at the lowest dose that produced effects, fat levels reached 449 ng/g, the same range already measured in roach and perch from Swiss lakes (44-166 ng/g lipid).

Moderate evidence: Rat adipose measured by GC-MS, n = 3-9; the fish comparison is to a cited 2004 Swiss survey, not measured here; no human tissue or breast-milk levels existed at the time.

Source: Schlumpf 2004, Toxicology Link to this fact

Fragrance is everywhere / Measured in people or real products

In winter Manhattan air the dominant terpene was limonene, the citrus scent chemical used in cleaners and personal care, while nearby forests gave off pine-type terpenes: scented products are a measurable source of city air pollution in New York.

Moderate evidence.

Source: Coggon 2021 Link to this fact

Fragrance is everywhere / Measured in people or real products

In New York City, everyday chemical products (paints, glues, cleaners, personal care) release about 50% more smog-forming vapor by weight than vehicles and other fossil fuels, and their tracers (D5-siloxane, ethanol) rise with population density across US and European cities.

Moderate evidence: NOAA FIVE-VCP inventory checked against tracer measurements; same group as McDonald 2018, so not an independent inventory method.

Source: Coggon 2021 Link to this fact

Fragrance is everywhere / Measured in people or real products

On New York's worst smog day of 2018, consumer and industrial chemical products added about 11 ppb of ozone to a 114 ppb regional peak (standard: 70 ppb), slightly more than vehicle and industry fuels (8 ppb).

Moderate evidence: Modeled attribution (WRF-Chem) for one heat-wave episode; the box model gives fossil fuels ~60% instead. Say 'comparable to vehicles'.

Source: Coggon 2021 Link to this fact

Fragrance is everywhere / Measured in people or real products

Scented product categories (personal care and cleaning) made about half of the ozone from consumer and industrial chemical products in New York, mostly through their alcohol and glycol solvents rather than the fragrance molecules.

Moderate evidence: Box-model budget, one city/episode; 'fragranced VCP' is a product category: fragrance compounds are ~6% of VCP ozone, oxygenates 24%, and ethanol 15%.

Source: Coggon 2021 Link to this fact

Fragrance is everywhere / Measured in people or real products

About two in three children's sunscreens (87 of 134) and toothpastes (40 of 61) in a Danish registry listed fragrance or a named fragrance allergen.

Moderate evidence: Label data, registry sample; Brazilian children's sunscreens were 34.5% (Uber 2024), so rates are market-specific.

Source: Botvid 2023, Contact Dermatitis Link to this fact

Fragrance is everywhere / Measured in people or real products

The more densely populated a US city center is, the higher its outdoor air levels of personal-care and fragrance-product chemicals relative to traffic pollution — a pattern found consistently across four different cities.

Moderate evidence: Correlational (R2 0.48-0.82 depending on compound); does not by itself prove causation or rule out other density-linked sources.

Source: Gkatzelis 2021, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

In summer Manhattan, citrus/pine-scent chemicals from fragranced products reached an outdoor air level comparable to benzene, a chemical that mostly comes from vehicle exhaust, even though the two come from completely different sources.

Moderate evidence: One city, one season, one compound class (monoterpenes); not a claim about total organic mass, ozone, or particle formation versus vehicles.

Source: Gkatzelis 2021, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

In a 2018 test of 18 hair products (hot oil, anti-frizz, leave-in conditioner, root stimulator, hair lotion, relaxer) commonly used by Black women, 45 of 66 targeted endocrine-disrupting and asthma-associated chemicals were detected, including every chemical class tested.

Moderate evidence: N=18 products, purchased 2008 based on a 2004-5 NYC usage survey; descriptive/exploratory, no statistical testing.

Source: Helm 2018, Environmental Research Link to this fact

Fragrance is everywhere / Measured in people or real products

In FDA's 2006 cosmetics survey, fragrance products carried the highest diethyl phthalate levels of any category tested (up to 3.9% by weight), and nail products carried the highest dibutyl phthalate levels (up to 6% by weight).

Moderate evidence: N=48 products, one purchasing round; category sizes as small as 1-9 products.

Source: Hubinger & Havery 2006, Journal of Cosmetic Science Link to this fact

Fragrance is everywhere / Measured in people or real products

A silicone ingredient in everyday deodorants, lotions, and hair products (D5) shows up in city outdoor air on a clear morning schedule tracking when people shower and dress for work, peaking around 6-7 AM and fading over the following several hours.

Moderate evidence.

Source: Coggon 2018, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

During the morning rush hour in a US city, the mass of a personal-care-product ingredient (the silicone D5) entering outdoor air can exceed 30% of the mass of benzene entering the air from vehicle traffic, and the city-wide daily D5 emission total is in the same order of magnitude as the city's traffic-benzene emissions.

Moderate evidence.

Source: Coggon 2018, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

In a study of 427 people smelling real body-odor samples, individuals stayed identifiable by smell even when wearing a deodorant, but any deodorant (their own or an assigned one) still made people significantly worse at telling them apart than smelling the unfragranced body odor alone.

Moderate evidence.

Source: Allen, Havlíček & Roberts 2015, Frontiers in Psychology Link to this fact

Fragrance is everywhere / Measured in people or real products

People were better at telling two individuals apart when both wore their own habitual deodorant than when both wore an unfamiliar, experimenter-assigned deodorant, consistent with fragrance choice tracking a person's own body chemistry rather than being arbitrary.

Moderate evidence.

Source: Allen, Havlíček & Roberts 2015, Frontiers in Psychology Link to this fact

Fragrance is everywhere / Government agency

The cosmetics industry's own safety panel (CIR) reported PTFE (Teflon) in 365 US cosmetic products in 2018, at up to 13% in mascara, 12% in eye shadow, 2.4% in hair bleach, and 0.5-3% in face and fragrance powders.

Moderate evidence: Self-reported by the industry to FDA's voluntary registration program and to the industry's own trade association survey; not independently audited.

Source: CIR 2018 Industry-funded Link to this fact

Fragrance is everywhere / Measured in people or real products

Using a statistical method that does not assume the answer in advance, scientists confirmed that everyday chemical products, not traffic, were the dominant source (about 70-78%) of the measured organic-vapor emissions at the New York City site, contributing roughly three-quarters of it, versus about a quarter in the much less crowded city of Boulder, Colorado.

Moderate evidence.

Source: Gkatzelis 2021b, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

In most U.S. cities, everyday chemical products likely account for 50 to 80% of the outdoor smog-forming and particle-forming potential from human activities, rivaling or exceeding vehicle traffic almost everywhere except the least densely populated areas.

Moderate evidence.

Source: Gkatzelis 2021b, Environmental Science & Technology Link to this fact

Fragrance is everywhere / Measured in people or real products

Health Canada's modeled median dermal DEP exposure for Canadian women from cosmetic and personal-care product use (2.6 ug/kg bw/d) independently matches a Korean team's measured estimate (2.017 ug/kg bw/d) from a different country's products and a different exposure-assessment method.

Moderate evidence: Both are modeled/estimated exposures based on product content and use-pattern surveys, not biomarker-confirmed doses; this is a median, not a worst-case, comparison.

Source: Koniecki 2011, Environmental Research Link to this fact

Fragrance is everywhere / Measured in people or real products

As early as the mid-1990s, the musk fragrance chemicals galaxolide (HHCB) and tonalide (AHTN) were already detectable in the body fat and breast milk of every German person tested, 19 out of 19 samples.

Moderate evidence: Small sample (14 adipose + 5 milk, one German region, 1993/1995); no product-use data or health outcome measured.

Source: Rimkus & Wolf 1996, Chemosphere Link to this fact

Fragrance is everywhere / Measured in people or real products

A 2015 survey of 817 unique detergent products from 131 German households found limonene and linalool — the two fragrance chemicals most often linked to skin allergy when oxidized — named on 23.1% and 20.1% of product labels, more than any of the other 24 EU-declarable fragrance allergens.

Moderate evidence: Label-declaration frequency above the EU's 0.01% threshold, not a chemical measurement; Northern Germany, 2015, convenience sample, not representative.

Source: Wieck 2018, Regulatory Toxicology and Pharmacology Link to this fact

Fragrance is everywhere / Measured in people or real products

Tumble drying real household laundry released 256-342 milligrams of textile microfiber per kilogram of fabric dried, whether the dryer vented outdoors or condensed the moisture indoors, a similar order of magnitude to what washing machines release.

Moderate evidence: One UK lab, one detergent, one condenser model, and one vented model, n=8 real loads per dryer type; measures plain cotton/polyester fiber, not fragrance or VOCs.

Source: Cummins 2023, PLOS ONE Industry-funded Link to this fact

Fragrance is everywhere / Self-reported survey

In a 1995 population-based telephone survey of 4,046 California adults, 15.9% said they were 'allergic or unusually sensitive to everyday chemicals' (like cleaning supplies, paints, perfumes, or soaps) and 6.3% reported a doctor's diagnosis of environmental illness or multiple chemical sensitivity.

Moderate evidence.

Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact

Fragrance is everywhere / Measured in people or real products

11 of 12 women with MCS, and none of 12 controls, developed headache and nausea during a brain-scanning session simply from smelling ordinary odorants (vanillin, acetone, cedar oil, lavender oil, eugenol, butanol) at levels used for a routine imaging study.

Moderate evidence.

Source: Hillert et al. 2007, Human Brain Mapping Link to this fact

Fragrance is everywhere / Other evidence

Personal care product use is nearly universal in the general population.

Moderate evidence: Single national survey; category definitions are broad (e.g., 'fragrance' includes perfume, cologne, and aftershave).

Source: Dales 2013, Annals of Epidemiology Link to this fact

Fragrance is everywhere / Other evidence

In a 36,446-subject Europe/US market-research survey, most people use only one type of deodorant rather than combining formats: 59% used roll-on only, 17% used spray only, and only about 2% used both spray and roll-on deodorant.

Moderate evidence.

Source: Comiskey 2015 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Fragrance is everywhere / Other evidence

The most common personal-care product combination in this 36,446-subject Europe/US survey was deodorant, oral care, and a shower product used together, at about 19% of subjects; only about 1% of men but about 7% of women used products from all 7 surveyed product categories.

Moderate evidence: This reflects only the 19 personal-care/cosmetic product types surveyed; it says nothing about household, laundry, or air-care product use, which were not included in this study.

Source: Comiskey 2015 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Fragrance is everywhere / Other evidence

In a 2016 barcode-scan inventory of 2,963 household products from 131 German homes, EU-regulated biocidal active substances (preservatives, disinfectants, insecticides, repellents) were found in every single household, and personal care products plus washing/cleaning agents accounted for 90% of all such ingredient observations, far outnumbering the biocidal products the regulation is actually built around.

Moderate evidence.

Source: Wieck 2016, Environment International Link to this fact

Fragrance is everywhere / Other evidence

Citric acid, methylisothiazolinone, phenoxyethanol, benzisothiazolinone, and the fragrance chemical geraniol were the five most commonly listed biocidal active substances in a 2016 scan of German household products, appearing on 859, 471, 409, 357, and 281 products respectively out of 2,963 scanned.

Moderate evidence.

Source: Wieck 2016, Environment International Link to this fact

Fragrance is everywhere / Review of other studies

Burning, stinging, or itching sensations in the eyes, nose, and throat from airborne chemicals are caused by a specific, receptor-mediated nerve reflex (activation of TRPV1, TRPA1, TRPM8, and related channels on trigeminal nerve endings), not by allergy or immune response.

Moderate evidence.

Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Fragrance is everywhere / Measured in people or real products

A home field study found that microfibers from a clothes dryer travel through outdoor air and land on the ground at least 30 feet from the vent, though most land within about 5 feet.

Moderate evidence.

Source: Kapp & Miller 2020, PLOS ONE Industry-funded Link to this fact

Fragrance is everywhere / Measured in people or real products

Even with a dryer's lint trap in place, tens of milligrams of lint still escape out the vent into outdoor air per drying cycle (35 mg at one home, 70 mg at a second home, averaged over three cycles).

Moderate evidence.

Source: Kapp & Miller 2020, PLOS ONE Industry-funded Link to this fact

Fragrance is everywhere / Measured in people or real products

Besides the fragrance-mix allergens, 14 other common fragrance materials (including linalool, benzyl acetate, and hedione) were found in 40-97% of the 73 deodorants tested in 1996; for three of them (hedione, linalyl acetate, alpha-isomethyl ionone) no published human contact-allergy case existed at the time despite their widespread use.

Moderate evidence.

Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact

Fragrance is everywhere / Measured in people or real products

Among 5,588 fragranced cosmetic products identified through a Danish consumer app, 85.5% of those labeled to contain at least one of the 26 EU-mandated fragrance allergens contained at least two, and 73.9% contained at least three; the 26 allergens were labeled 17,870 times in total across the products (mean 3.2 per product).

Moderate evidence: Label survey (declared ingredients only, no chemical analysis); self-selected app-user sample, not a market-representative survey.

Source: Bennike 2017/2018 Link to this fact

Fragrance is everywhere / Measured in people or real products

Unlike the classic hazardous air pollutants in the same 482-deodorant survey (formaldehyde, benzene, methanol, ethylene oxide, trichloroethylene, chloroform), which each appeared in only 0.4-13.7% of products at generally low concentration, the two intentionally added biocides (chlorine dioxide, silver) and the fragrance allergens were found far more consistently and at far higher concentrations, consistent with the classic HAPs being incidental base-formulation contaminants rather than deliberately added ingredients.

Moderate evidence.

Source: Kim et al. 2018, Science of The Total Environment Link to this fact

Fragrance is everywhere / Other evidence

More than 2,000 chemical substances, of which 300 to 400 are of natural origin, are used across the fragrance industry, and a single perfume can contain from a few to several hundred individual fragrance materials.

Moderate evidence: Industry-wide chemical count from a single review citing an industry-adjacent source (ref 10); see the broader chemical-count provenance problem.

Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact

Fragrance is everywhere / Advocacy group testing

The UV filter ethylhexyl methoxycinnamate, found in several of the tested perfumes, and limonene, one of the most common fragrance ingredients, are both flagged by this report as environmentally problematic; the EU classifies limonene as very toxic to aquatic life.

Moderate evidence.

Source: Tegengif 2022 Link to this fact

Fragrance is everywhere / Self-reported survey

Among 718 non-smoking Saudi university students surveyed in 2020, 65.7% (472) reported using scented candles, and usage was far more common among women (74.9% of female respondents) than men (28.4% of male respondents, chi-square p=0.0001).

Moderate evidence: Convenience/snowball sample recruited via WhatsApp and Twitter, not a probability sample; may not generalize beyond young, social-media-active Saudi university students.

Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact

Fragrance is everywhere / Government agency

Endocrine disruptors can combine to produce a 'cocktail effect': a mixture of several endocrine disruptors, each too dilute on its own to cause a detectable effect, can still produce an adverse effect together.

Moderate evidence: The Commission cites this as a general, growing evidence base, not as a demonstrated effect for any specific consumer-product combination.

Source: EU Commission 2018 Link to this fact

Fragrance is everywhere / Measured in people or real products

Matching the ingredient lists of 7,603 Korean household chemical products (cleaners, synthetic detergents, fabric softeners, air fresheners, deodorants) against a hormone-disruption hazard database found 293 flagged chemicals, and nearly two out of three products listed more than one of them.

Moderate evidence: Counts ingredient-list matches against EPA ToxCast/CompTox hazard flags, not measured concentrations or confirmed toxicity in the products as sold; single-country database study.

Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact

Fragrance is everywhere / Other evidence

Researchers found multiple fragrance sources (cosmetics, air fresheners, cleaning/laundry products, fragrance-emitting devices, or candles) in every one of the 37 homes they surveyed for a chemical-intolerance study.

Moderate evidence.

Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact

Fragrance is everywhere / Measured in people or real products

In a study of 164 pregnant women in New York City, the phthalate metabolites MEP and MnBP were detected in 100% of urine samples.

Moderate evidence.

Source: Just 2010 (or equivalent NYC pregnant-women cohort), Journal of Exposure Science and Environmental Epidemiology Link to this fact

Green, natural and unscented / Review of other studies

Products labeled unscented can still contain a fragrance added to mask other smells.

Moderate evidence.

Source: Kumar 2020, Journal of Cosmetic Dermatology Link to this fact

Green, natural and unscented / Measured in people or real products

In 14 of 17 'alternative' (mostly green-marketed) products that contained fragrance chemicals, the label never mentioned fragrance.

Moderate evidence: Mostly natural terpenes at low levels; single products from one retailer.

Source: Dodson 2012, Environmental Health Perspectives Link to this fact

Green, natural and unscented / Measured in people or real products

Products labeled 'green,' 'natural' or 'non-toxic' released hazardous chemicals too, with no significant difference from ordinary ones in a test of 25 best-sellers.

Moderate evidence: 11 vs 14 products; underpowered; list-membership counts; small sample (11 vs 14 products, p>0.30): a null result, not proof of equality.

Source: Steinemann 2011, Environmental Impact Assessment Review Link to this fact

Green, natural and unscented / Measured in people or real products

Baby products labeled green, organic, or natural released no fewer chemicals than regular ones (398 vs 286 detections), and 20 of 21 in each group released at least one chemical classed as potentially hazardous.

Moderate evidence: Headspace counts, not concentrations; agrees with Lin 2020 and Steinemann 2011.

Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact

Green, natural and unscented / Measured in people or real products

Natural baby products swapped one scent chemistry for another: linalool, a common fragrance allergen once it oxidizes, turned up in 16 of 21 green products vs 4 of 21 regular ones.

Moderate evidence.

Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact

Green, natural and unscented / Animal study

'Natural' doesn't mean allergy-free: essential oils oxidize too; in mouse tests lavender oil exposed to air for 45 weeks became about 8 times more potent as a sensitizer (EC3 36% fresh, 4.4% aged), and oxidized alpha-terpinene from tea tree oil was the most potent of all.

Moderate evidence.

Source: Karlberg 2013, Contact Dermatitis Link to this fact

Green, natural and unscented / Self-reported survey

Three in four UK adults (75.0%) did not know that products called natural, green, or organic can also release hazardous air pollutants, and more than half (53.5%) said they would stop using a product if they knew.

Moderate evidence: Awareness item; the emission claim itself rests on other studies.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Green, natural and unscented / Measured in people or real products

Plant-derived scent chemicals drove the particle bursts, so a 'natural' citrus or pine scent is not automatically cleaner to breathe.

Moderate evidence: No unscented comparison in this study.

Source: Rosales 2022, Science Advances Link to this fact

Green, natural and unscented / Measured in people or real products

Labels are not a guarantee: ethyl and butyl paraben actually rose after girls switched to paraben-free-labeled products, probably because some replacements contained them.

Moderate evidence: Replacement products were not tested; explanation inferred.

Source: Harley 2016, Environmental Health Perspectives Link to this fact

Green, natural and unscented / Journalism

A 2009 audit of 2,219 North American products making green claims found that more than 98% made at least one misleading or unsupported environmental claim.

Moderate evidence: TerraChoice gray literature; auditor sells eco-certification; audits substantiation not chemistry.

Source: Dahl 2010, Environmental Health Perspectives Link to this fact

Green, natural and unscented / Journalism

Green-claim auditors named 'all-natural' as a textbook example of a vague green claim and called household cleaning-product makers 'among the worst greenwash offenders'.

Moderate evidence: Opinion of TerraChoice staff; '3 of 397 cleaners' figure not text-verified.

Source: Dahl 2010, Environmental Health Perspectives Link to this fact

Green, natural and unscented / Measured in people or real products

In a test of 79 US feminine hygiene products, labels such as organic, natural, or for sensitive skin did not predict lower levels of volatile chemicals.

Moderate evidence: Product content, not exposure; small subgroups.

Source: Lin 2020, Environment International Link to this fact

Green, natural and unscented / Journalism

Perfumers themselves say every perfume blends synthetic and natural materials: "As all perfumers, I create perfume formulas with both synthetic and natural perfumery raw materials" (a Charabot perfumer). A "natural" scent is rarely all natural.

Moderate evidence: One perfumer's essay; no proportions given; industry author.

Source: Ellena 2008, Chemistry & Biodiversity Industry-funded Link to this fact

Green, natural and unscented / Self-reported survey

'Natural' essential oils have not been shown safe for hormone-sensitive children: the only survey claiming so had about a 5% chance of detecting even a tripling of risk.

Moderate evidence: Power figure is evidence base arithmetic from the paper's group sizes and observed baseline; absence of proof of safety is not proof of harm.

Source: Hawkins 2021, International Journal of Pediatrics and Adolescent Medicine Industry-funded Link to this fact

Green, natural and unscented / Review of other studies

Many products sold as "fragrance free" in natural-product stores are free only of synthetic fragrance and still contain essential oils, which make up 80 of the 162 fragrance ingredients documented to cause skin allergy.

Moderate evidence.

Source: Rodriguez 2024, Cutis Link to this fact

Green, natural and unscented / Lab study (cells or chemistry)

'Natural' scent is not biologically inert: essential oils such as lavender and tea tree are chemical mixtures, and in lab tests they acted on estrogen and androgen receptors.

Moderate evidence: Shows biological activity, not harm at use levels.

Source: Henley 2007, New England Journal of Medicine Link to this fact

Green, natural and unscented / Review of other studies

Even a review that found little evidence of harm from lavender and tea tree oil in children warned that 'a lack of evidence of harm cannot be interpreted as evidence of safety' for essential oils in children's products.

Moderate evidence: Direct quote; the review's own conclusion is that the link is unsupported.

Source: Hawkins 2020, Complementary Therapies in Medicine Industry-funded Link to this fact

Green, natural and unscented / Lab study (cells or chemistry)

Natural does not mean hormonally inert: the hormone-active chemicals tested here are ordinary constituents of lavender and tea tree essential oils, not synthetic fragrance chemicals.

Moderate evidence: Cell assays only, at concentrations far above plausible human exposure; whole-animal guideline tests of the two main lavender constituents were negative.

Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact

Green, natural and unscented / Lab study (cells or chemistry)

Terpenes do not behave alike: alpha-terpineol and terpinen-4-ol were the most hormone-active of the eight essential-oil chemicals tested, while eucalyptol was inactive on both the estrogen and the androgen receptor.

Moderate evidence: Receptor assays only; eucalyptol is separately reported to inhibit the steroid-synthesis enzyme CYP17A1, which this study did not test.

Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact

Green, natural and unscented / Measured in people or real products

A fragrance-free body lotion still gave the highest VOC emissions measured in the study, mostly from a preservative (likely phenoxyethanol), and its plant oils reacted with ozone to form aldehydes such as nonanal and nonenal.

Moderate evidence: One lotion, 4 men, chamber; phenoxyethanol identity inferred from PTR-MS ions and the ingredient list.

Source: Wang 2024, Environmental Science & Technology Link to this fact

Green, natural and unscented / Lab study (cells or chemistry)

There is no known 'safe terpene'. Eucalyptol is inactive on hormone receptors but acts weakly on a hormone-making enzyme; alpha-terpineol is the most active on receptors and only middling on the enzyme; limonene is near-inert on receptors and a comparable enzyme inhibitor. The two rankings disagree in both directions.

Moderate evidence: Both rankings are in vitro and at concentrations far above real exposure. The point is that one screen does not clear a molecule, not that any of these molecules is proven harmful.

Source: Sharma 2024 + Ramsey 2019, Biomolecules Link to this fact

Green, natural and unscented / Review of other studies

Natural exfoliants such as salt, sugar, ground seeds or shells, and cellulose beads can replace plastic microbeads.

Moderate evidence: Environmental substitution only; skin safety of the alternatives was not assessed.

Source: Han & Kim 2025, Cosmetics Link to this fact

Green, natural and unscented / Review of other studies

Essential oils oxidize in air into the same allergens as synthetic fragrance, and 'natural' cosmetics routinely carry fragrance allergens: 91% of 'natural' perfumes on the Danish market contained at least one target fragrance sensitizer (chemical analysis, 1996) — but only 35% of the other 'natural' cosmetics (shampoos, creams, lotions) in the same study did, at far lower concentrations — and 82 of 100 European natural-brand products checked in 2013-15 listed at least one allergen on the label.

Moderate evidence.

Source: Pastor-Nieto 2021 (Rastogi 1996; Klaschka 2016), Current Treatment Options in Allergy Link to this fact

Green, natural and unscented / Measured in people or real products

In a check of 100 'natural' personal-care products from 10 European natural-cosmetics brands, 82 listed at least one of the EU's labeled fragrance allergens (up to 11 in one product); limonene was on 71 labels and linalool on 70.

Moderate evidence: Label declarations only, no chemical analysis; 10 products from each of 10 anonymous brands, not representative; 2013-15, when the EU list had 26 allergens.

Source: Klaschka 2016, Environmental Sciences Europe Link to this fact

Green, natural and unscented / Measured in people or real products

'For sensitive skin' is not a promise of no fragrance allergens: all 15 natural products named 'sensitive', 'soothing' or 'soft' listed between 1 and 7 of the EU's labeled fragrance allergens.

Moderate evidence: N=15 products, labels only, European natural brands.

Source: Klaschka 2016, Environmental Sciences Europe Link to this fact

Green, natural and unscented / Measured in people or real products

In a 2016 survey of 174 best-selling US body moisturizers, 18 of the 40 labeled "fragrance free" (45%) still listed at least one ingredient that dermatologists' allergen database (ACDS CAMP) flags for fragrance-allergic patients.

Moderate evidence.

Source: Xu 2017, JAMA Dermatology Link to this fact

Green, natural and unscented / Measured in people or real products

Among the same best-selling US moisturizers, 15 of 18 labeled "hypoallergenic" (83%) and 95% of those labeled "dermatologist recommended" contained at least one common skin allergen; only 12% of all products contained none.

Moderate evidence: Listed allergens (NACDG series), not reactions; label data, 2016 formulations.

Source: Xu 2017, JAMA Dermatology Link to this fact

Green, natural and unscented / Measured in people or real products

All 16 UK day face moisturizers tested gave off fragrance terpenes (measured together as 'limonene'), and the 8 'green'-marketed ones released the same amount as the 8 regular ones (0.25 vs 0.26 µg per second per gram), as well as the same ethanol.

Moderate evidence.

Source: Yeoman 2022, Indoor Air Link to this fact

Green, natural and unscented / Review of other studies

In 1999 a dermatologist listed ten US "fragrance-free" skin products that named fragrance chemicals in their own ingredient lists, including a "fragrance-free" cleansing bar containing rose, rosewood, cedarwood, and almond oils; one manufacturer admitted the benzaldehyde in its fragrance-free product was there to mask an unpleasant smell.

Moderate evidence.

Source: Scheinman 1999, Journal of the American Academy of Dermatology Link to this fact

Green, natural and unscented / Measured in people or real products

In a 1996 Danish GC-MS analysis, 91% (20 of 22) of perfumes marketed as based on natural ingredients contained 1 to 7 of 11 well-known fragrance sensitizers at concentrations up to 7.7%, including one perfume with 6.04% hydroxycitronellal — above the concentration shown to sensitize 36% of healthy volunteers in patch testing.

Moderate evidence.

Source: Rastogi 1996, Contact Dermatitis Link to this fact

Green, natural and unscented / Measured in people or real products

The same 1996 study found far fewer fragrance sensitizers in other 'natural' cosmetics (shampoos, creams, lotions, deodorants, massage oils): only 35% (7 of 20) contained 1-3 of the target substances, at concentrations (0.0003-0.082%) roughly 100x lower than the natural perfumes.

Moderate evidence: Small non-representative sample (n=20); shows fragrance-sensitizer exposure from 'natural' products is concentrated in perfume-type products, not uniform across the category.

Source: Rastogi 1996, Contact Dermatitis Link to this fact

Green, natural and unscented / Review of other studies

Essential oils are complex mixtures of hundreds of components whose composition varies by producer, plant origin, climate, and extraction method, so a product labeled as containing 'lavender oil' or 'tea tree oil' does not guarantee a fixed chemical composition or a fixed level of biological activity.

Moderate evidence: Stated as general essential-oil chemistry background in this review; not measured for any specific consumer product here.

Source: Ramsey 2020 (YJBM), Yale Journal of Biology and Medicine Link to this fact

Green, natural and unscented / Self-reported survey

More than half of Germans (55.6%) wrongly believe products with natural fragrance ingredients are healthier than products with synthetic ones, and the false belief is highest (67-69%) among people who read ingredient labels or prefer fragrance-free products.

Moderate evidence: Belief survey, not a chemical measurement; the 'wrong' judgment is the author's own hazard-classification argument, not tested in this paper.

Source: Klaschka 2020a, Environmental Sciences Europe Link to this fact

Green, natural and unscented / Measured in people or real products

A headspace test of the fragranced and fragrance-free versions of the same detergent brand found 34 volatile chemicals in the fragranced version but only 7 in the fragrance-free version, and no fragrance terpenes (such as D-limonene or linalool) at all in the fragrance-free version.

Moderate evidence: Single product pair tested (one Australian brand); presence/absence only, not a full quantitative comparison.

Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact

Green, natural and unscented / Government agency

Allergy UK's Product Endorsement Scheme is run by Allergy Research Ltd, a private limited company that is a legally separate trading subsidiary of the charity British Allergy Foundation (which operates publicly as Allergy UK); ARL donates its profits to the charity.

Moderate evidence: Organizational/legal fact stated plainly on the page itself; not independently verified against Companies House or charity filings.

Source: Allergy UK 2026 Link to this fact

Green, natural and unscented / Government agency

On the page describing its Product Endorsement Scheme, Allergy UK publishes no fragrance-specific criteria: the word "fragrance" does not appear anywhere on the page, and the only stated assurance is that a product has been "scientifically tested by Allergy UK to confirm its claims," with no ingredient list, protocol, or threshold given.

Moderate evidence: Absence of published criteria on this page is not proof the underlying testing process lacks criteria internally; it is only what the public page discloses.

Source: Allergy UK 2026 Link to this fact

Green, natural and unscented / Government agency

EPA's Safer Choice fragrance-free certification is a documentary ingredient-list review, not a finished-product lab test: EPA checks that a product already meets the full Safer Choice Standard, then checks its ingredient list against the industry's own IFRA Transparency List of fragrance materials.

Moderate evidence.

Source: US EPA Safer Choice Link to this fact

Green, natural and unscented / Government agency

A product carrying the EPA Safer Choice 'fragrance-free' label can still have a smell, because ordinary functional ingredients such as surfactants and solvents can carry an odor without being classified as a fragrance material.

Moderate evidence: EPA states this directly; it is a definitional carve-out, not a measurement of any certified product's actual odor.

Source: US EPA Safer Choice Link to this fact

Green, natural and unscented / Government agency

Health Canada's cosmetic labeling guidance on 'unscented'/'fragrance-free' does not cover laundry detergent, fabric softener, or dryer sheets; Canada's legal definition of 'cosmetic' (Food and Drugs Act s.2) covers products for the complexion, skin, hair, or teeth, not fabric.

Moderate evidence.

Source: Health Canada 2026 Link to this fact

Green, natural and unscented / Measured in people or real products

Laundry products labeled 'free and gentle' genuinely excluded fragrance (0% contained it across every product category), but still commonly contained preservative allergens (MI in 57.1% of free-and-gentle detergents) and surfactant allergens (decyl/lauryl glucoside in 28.6-33.3% of free-and-gentle detergents and stain removers).

Moderate evidence: N=7-13 per free-and-gentle subgroup depending on category; label survey only.

Source: Bai 2020, Dermatitis® Link to this fact

Green, natural and unscented / Measured in people or real products

In the same test house and wax warmer, an unscented wax melt produced no significant terpene release and no measurable nanoparticle formation, showing that the fragrance chemicals — not the melted wax itself — are what drives the particle-forming reaction.

Moderate evidence: A single unscented product tested as one control condition; supports the mechanism but is not itself a survey of unscented products generally.

Source: Patra et al. 2025, Environmental Science & Technology Letters Link to this fact

Green, natural and unscented / Review of other studies

Most 'natural' or herbal deodorant actives described in this review (essential oils such as tea tree and usnic acid, and dozens of herbal extracts) work the same way synthetic actives like triclosan and silver compounds do: by killing or inhibiting the skin bacteria that cause odor, not through some fundamentally gentler mechanism.

Moderate evidence: Based on antibacterial potency (MIC/MBC) data only; this review does not compare skin-irritation or sensitization rates between herbal actives and synthetic anti-microbial salts.

Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact

Green, natural and unscented / Measured in people or real products

The unscented 'plain' paraffin candle used as this study's own combustion reference produced the third-highest formaldehyde level of the six candles tested when lit (925 ppb), higher than two of the five scented candles.

Moderate evidence.

Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact

Green, natural and unscented / Measured in people or real products

A series of six men's grooming products from one brand were marketed with the text 'Our products never contain artificial colors, synthetic fragrances' while labeled to contain Evernia furfuracea (tree moss) extract, a natural-source fragrance allergen.

Moderate evidence: Single-brand example (n=6 products from one line), not a systematic audit of 'natural' marketing claims.

Source: Bennike 2017/2018 Link to this fact

Green, natural and unscented / Measured in people or real products

Not all fragrance-based odor masking works the same way: Iso E Super, a common deodorant fragrance chemical that barely blocked the malodor receptors in lab dish tests, still reduced how strong a sulfur malodor smelled to people, but less effectively than beta-ionone, suggesting this masking runs mainly through the brain blending two smells together rather than through receptor blocking.

Moderate evidence: Central-processing explanation is the authors' inference from a negative in-vitro result, not directly tested; based on the same single-lab, single-cohort study.

Source: Fukutani et al. 2023, Current Biology Industry-funded Link to this fact

Green, natural and unscented / Measured in people or real products

Ethanol, linalool, and D-limonene, common fragrance and solvent terpenes found in both synthetic and "natural" scented products, were the single most-listed chemicals overall (about 27%, 16%, and 12% of products respectively) in a database of over 7,000 Korean household chemical products, ahead of synthetic fragrance aldehydes like hexyl cinnamaldehyde (about 8%).

Moderate evidence: Ingredient-list prevalence, not measured air or dermal exposure; does not distinguish products marketed as "natural"/"green" from conventional ones.

Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact

Green, natural and unscented / Government agency

EPA's own advice for preventing unpleasant household odors is proper ventilation and basic household cleanliness, not air fresheners or fragranced products.

Moderate evidence: Stated in the context of moth-repellent/paradichlorobenzene odor, not a general product-safety recommendation.

Source: US EPA, "The Inside Story" Link to this fact

Health effects / Self-reported survey

In a national survey of 1,098 Australian adults, one in three (33%) said fragranced products such as air fresheners, cleaners, and perfume gave them health problems, most often breathing trouble, migraines, and skin reactions.

Moderate evidence: Self-report; same dataset as Steinemann 2018 AU asthmatics, 2018 AU MCS, and 2019 AU arm (362/1,098 reconfirmed in the MCS paper's Table 1; not a replication).

Source: Steinemann 2017, Preventive Medicine Reports Link to this fact

Health effects / Self-reported survey

In national surveys of 4,435 adults in the US, Australia, the UK, and Sweden, about 1 in 3 (32%) said fragranced products such as air fresheners, scented cleaners, or other people's perfume cause them health problems.

Moderate evidence: Self-report; any symptom from any product counts; pooled re-analysis of previously published surveys; the US arm (34.7%) is the same dataset as four US papers.

Source: Steinemann 2019, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

About 1 in 8 adults (12.6%) in four countries said fragranced products trigger migraine headaches, and 7% said they trigger asthma attacks.

Moderate evidence: Self-report; no diagnosis check.

Source: Steinemann 2019, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

In a national US survey, about two in three adults with asthma (64.3%) said fragranced products made them ill, compared with about one in four (23.8%) of people without asthma.

Moderate evidence.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

27.9% of US adults with asthma said fragranced products had triggered asthma attacks.

Moderate evidence.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

In a random-based sample of 946 Danish adults, 42% said fragranced products gave them eye, nose, or breathing symptoms in the past year (50% of women, 30% of men).

Moderate evidence: Self-attributed symptoms; sample enriched for allergy at baseline.

Source: Elberling 2005, Clinical and Experimental Allergy Link to this fact

Health effects / Self-reported survey

Among people with symptoms, 56% named other people's perfume, 32% air fresheners, and 28% other people's freshly washed (fabric-softened) clothes as triggers.

Moderate evidence: Self-report.

Source: Elberling 2005, Clinical and Experimental Allergy Link to this fact

Health effects / Self-reported survey

About 1 in 7 Danish adults (14%) reported fragrance-triggered symptoms at least weekly, and 5% had changed where they shop, how they travel, or how they work because of them.

Moderate evidence: Self-report.

Source: Elberling 2005, Clinical and Experimental Allergy Link to this fact

Health effects / Measured in people or real products

Standard allergy tests did not predict who reacted to fragrance; people with sensitive airways (including non-allergic asthma) were 2-4 times more likely to react, pointing to airway irritation rather than classic allergy.

Moderate evidence.

Source: Elberling 2005, Clinical and Experimental Allergy Link to this fact

Health effects / Self-reported survey

In a national survey of 1,100 Swedish adults, one in three (33.1%) said fragranced products gave them health problems, most often breathing difficulties (20.0%) and migraines (16.1%).

Moderate evidence.

Source: Steinemann 2018 (Sweden), Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

In a nationally representative survey of 1,136 US adults, 34.7% said fragranced products such as air fresheners, cleaners, and perfume gave them health problems, most often breathing difficulties, eye/nose irritation, or migraine.

Moderate evidence.

Source: Steinemann 2016, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

In a national survey of 1,098 Australian adults, more than half of those with asthma or an asthma-like condition (55.6%) said fragranced products made them ill, against about a quarter (23.9%) of people without asthma.

Moderate evidence.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

About 1 in 4 Australian adults with asthma (24.0%) said a fragranced product had triggered an asthma attack; air fresheners were the most common trigger (14.1% of all asthmatics).

Moderate evidence: Self-report; consistent with US and Danish samples (~34-43% airway symptoms).

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Health effects / Review of other studies

Cleaning products were the suspected exposure in 236 of 1,915 (12%) confirmed work-related asthma cases across California, Massachusetts, Michigan, and New Jersey (1993-1997); in California, janitors and cleaners had roughly double the confirmed-case rate of all other occupations combined (4.3 vs 2.3 per 100,000 workers).

Moderate evidence.

Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact

Health effects / Self-reported survey

In a US national survey, about 1 in 5 adults (20.4%) said air fresheners gave them health problems such as breathing difficulty, migraine, or asthma attacks.

Moderate evidence: Restated from Steinemann 2016 survey; cite the primary; self-report.

Source: Steinemann 2017, Building and Environment Link to this fact

Health effects / Self-reported survey

In a nationally representative survey of 1,100 UK adults, 27.8% said fragranced products such as air fresheners, cleaners, or perfume gave them health problems, including migraines (8.4%) and asthma attacks (6.8%).

Moderate evidence: Self-report, any symptom; same data as Steinemann 2019 UK arm.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Health effects / Review of other studies

In a small double-blind, randomized lab test (Ternesten-Hasséus 2002, the primary study behind this review's capsaicin-challenge claim), 12 people with multiple chemical sensitivity coughed significantly more than 12 matched healthy controls at every capsaicin dose tested (P<0.05 to P<0.005), a sign that their airway irritant nerves are oversensitive.

Moderate evidence.

Source: Molot 2023, Neuroscience and Biobehavioral Reviews Link to this fact

Health effects / Measured in people or real products

Estimated cancer risks were below one in a million for most feminine hygiene product types; washes (3.3 in a million) and sprays/powders (2.1 in a million) were just above that level under worst-case assumptions.

Moderate evidence: Modeled upper-bound scenario.

Source: Lin 2020, Environment International Link to this fact

Health effects / Lab study (cells or chemistry)

In lab studies, common flavor and fragrance chemicals act directly on TRPA1, the nerve receptor that senses irritants such as mustard oil: cinnamon's cinnamaldehyde and thyme's thymol switch it on, while camphor and eucalyptus oil block it.

Moderate evidence: Cell and animal pharmacology; the review's framing is therapeutic, not hazard.

Source: Mihara & Shibamoto 2015, Allergy, Asthma & Clinical Immunology Link to this fact

Health effects / Measured in people or real products

In a double-blind lab test where people could not smell it, perfume vapor piped to one eye caused more eye irritation than clean air in 10 of 42 people, including 2 healthy volunteers: perfume can irritate the eyes without being smelled.

Moderate evidence.

Source: Elberling 2006, Indoor Air Link to this fact

Health effects / Measured in people or real products

The eye irritation from perfume vapor was not an allergy: people patch-test allergic to the very same perfume were no more likely to react than those who were not.

Moderate evidence.

Source: Elberling 2006, Indoor Air Link to this fact

Health effects / Measured in people or real products

In a Toronto clinic for work-related breathing problems, about 1 in 10 referred workers had an irritable larynx (throat) syndrome rather than asthma; perfumes and cleaning agents, bleaches and air fresheners were among the named triggers.

Moderate evidence.

Source: Hoy 2010, Occupational Medicine Link to this fact

Health effects / Measured in people or real products

About 80% of workers with scent- and irritant-triggered irritable larynx syndrome were women, versus 24–52% of workers with occupational asthma at the same clinic.

Moderate evidence: N=30, one clinic; referral and care-seeking may differ by sex.

Source: Hoy 2010, Occupational Medicine Link to this fact

Health effects / Measured in people or real products

Scent-triggered throat and breathing reactions can mimic asthma but do not respond to asthma inhalers; almost two-thirds of these patients had been prescribed asthma medication anyway.

Moderate evidence.

Source: Hoy 2010, Occupational Medicine Link to this fact

Health effects / Measured in people or real products

An older, unblinded human study (Stewart 1970) reported eye, nose, and throat irritation from PGME solvent vapor at 250 ppm in 23 subjects across five experimental runs, and odor tolerance developing within 25 minutes in 6 subjects at 100 ppm; a later double-blind study with objective eye measurements (Emmen 2003) found no objective eye effects at up to 150 ppm and only very slight subjective eye discomfort at 150 ppm, but did not test 250 ppm.

Moderate evidence.

Source: CIR 2008 (citing Stewart 1970), International Journal of Toxicology Industry-funded Link to this fact

Health effects / Animal study

Citronellol, a rose-scented fragrance ingredient present in about half of household products, crosses the blood-brain barrier: brain-to-blood ratios were 0.5-0.8 in fish, up to 0.6 in mice, and 0.77 in a laboratory barrier built from human brain cells.

Moderate evidence: BBB crossing is measured and dose-independent as a property, but the doses used were far above consumer exposure; routes were waterborne and oral, not inhalation or skin.

Source: Kim 2024, Journal of Hazardous Materials Link to this fact

Health effects / Animal study

At high doses in zebrafish and mice, citronellol pushed tryptophan metabolism toward 3-hydroxykynurenine, a neurotoxic metabolite, and produced brain inflammation, roughly double the oxidative stress, a five-fold rise in dying brain cells, a leaky blood-brain barrier, and anxiety-like behavior.

Moderate evidence: Zebrafish 2-8 mg/L in water; mice 345-3450 mg/kg by gavage (top dose = an LD50); 10^5-10^6 times estimated human exposure; male mice only.

Source: Kim 2024, Journal of Hazardous Materials Link to this fact

Health effects / Animal study

Citronellol's effect on the brain reverses with dose: protective in a rat Parkinson's-disease model at 25 mg/kg oral (given as a month-long pretreatment before each day's toxin dose, not as treatment of existing damage), damaging at 345 mg/kg and above in a different paper, species and route.

Moderate evidence.

Source: Kim 2024, Journal of Hazardous Materials Link to this fact

Health effects / Review of other studies

Salicylate fragrance chemicals pass through skin and are converted in the body to salicylic acid, the compound aspirin becomes: for methyl salicylate (wintergreen), human studies found roughly 12-30% of an applied dose absorbed.

Moderate evidence.

Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact

Health effects / Animal study

Mice breathing the vapor of five ordinary commercial colognes for one hour showed airway irritation and a 30-35% drop in mid-expiratory airflow, despite never having been exposed to any allergen or asthma trigger.

Moderate evidence.

Source: Anderson & Anderson 1998, Archives of Environmental Health Link to this fact

Health effects / Measured in people or real products

Over 20 years (1993–2012), California's work-related asthma surveillance confirmed 270 cases linked to perfume or air fresheners at work, 3.8% of all confirmed cases; perfume was the 9th most common workplace asthma exposure.

Moderate evidence: Surveillance count of physician-diagnosed, reported cases; misses >=2/3 of cases; no objective testing required; excludes fragranced cleaners.

Source: Weinberg 2017, Journal of Asthma Link to this fact

Health effects / Measured in people or real products

94% of workers with fragrance-related work asthma in California were women, mostly in offices, health care, and schools, and most cases came from perfume worn by others.

Moderate evidence: Authors attribute the sex skew to occupation and exposure, not susceptibility; care-seeking bias possible.

Source: Weinberg 2017, Journal of Asthma Link to this fact

Health effects / Self-reported survey

Many people with chemical sensitivities delay or avoid medical care because clinics and hospitals are heavily scented; healthcare was named as one of the least accessible settings (31 of 60).

Moderate evidence: Qualitative, self-selected Canadian sample; frequency of care avoidance not quantified.

Source: Roy 2026 Link to this fact

Health effects / Review of other studies

People adapt to a steady odor, so a constant background scent stops being noticed while it is still in the air.

Moderate evidence.

Source: Dalton & Jaén 2010, Current Opinion in Allergy and Clinical Immunology Industry-funded Link to this fact

Health effects / Self-reported survey

In a nationally representative German survey, half of the people who get sick from fragranced products (51.1%) had been kept from going somewhere because of fragrance, and 43.8% had avoided public toilets with air fresheners or scented products.

Moderate evidence: Self-report; Germany 2019, n=219 fragrance-sensitive of 1,102; same data as Steinemann & Klaschka 2019.

Source: Klaschka 2020, Environmental Sciences Europe Link to this fact

Health effects / Review of other studies

Fragrance can cause skin allergy without touching your own products: from a partner's toiletries (consort dermatitis), from soap residue carried on the hands to the eyelids, and through the air, as in a small case series of a ride-share driver and four passengers whose airborne facial/eyelid dermatitis (all patch-test positive for fragrance mix I and/or balsam of Peru) was linked to car fragrance diffusers, with the driver's rash clearing when his diffuser was removed.

Moderate evidence.

Source: Rodriguez 2024, Cutis Link to this fact

Health effects / Lab study (cells or chemistry)

In lab tests on human cells, both lavender oil and tea tree oil switched on estrogen-receptor signaling (about half the maximum effect of the body's own estradiol) and blocked testosterone-type (androgen-receptor) signaling by 41–52%.

Moderate evidence.

Source: Henley 2007, New England Journal of Medicine Link to this fact

Health effects / Lab study (cells or chemistry)

Lavender oil and tea tree oil activated the human estrogen receptor in cell assays to about 17-18% of the response to estradiol, and blocked testosterone signaling more completely than flutamide, a prescription anti-androgen drug.

Moderate evidence.

Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact

Health effects / Review of other studies

If a young child has unexplained early breast development, it is reasonable to ask about lavender and tea tree products, including room diffusers, and try stopping them – which is what the study's authors recommend to doctors.

Moderate evidence: This is the authors' clinical recommendation, not a proven treatment; they explicitly state they are not recommending that anyone avoid these products generally.

Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact

Health effects / Self-reported survey

Of all personal care product types, perfumes and colognes had the highest hazard ratings in the Environmental Working Group's Skin Deep database, and adults aged 18–39 used the highest-rated ones (average 7.2 of 10, vs 5.9 for those 60 and over).

Moderate evidence: EWG hazard ratings from listed ingredients, not measured toxicity or exposure; 39% of perfumes used could not be rated.

Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact

Health effects / Self-reported survey

Black women in a US university sample were twice as likely as White women to have recently used a hair product rated high-hazard by EWG (relative risk 1.99, 95% CI 1.37–2.89).

Moderate evidence.

Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact

Health effects / Lab study (cells or chemistry)

Essential-oil terpenes can interfere with the enzymes that BUILD hormones, not just the receptors hormones act on — a route that the standard estrogen- and androgen-receptor safety screens are not designed to detect.

Moderate evidence: Mechanistic point only. The measured effects were weak (13–33%) and all at a single 10 µM with no dose–response.

Source: Sharma 2024, Biomolecules Link to this fact

Health effects / Lab study (cells or chemistry)

The antibacterial triclosan, once in about 45% of US soaps, reacts to UVB at an intensity matched to real midday sunlight by generating free radicals that damaged human skin cells (HaCaT keratinocytes) in the laboratory, dose-dependently and only when triclosan and radiation were combined.

Moderate evidence.

Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact

Health effects / Review of other studies

A 2024 safety review by an industry toxicologist states there are no data on whether PTFE passes through the skin, how the body handles it, or whether it affects hormones, and that it does not biodegrade.

Moderate evidence.

Source: Jomaa 2024, Journal of the Netherlands Society of Toxicology (JNST) Industry-funded Link to this fact

Health effects / Lab study (cells or chemistry)

In a 2025 lab screen of 42 everyday perfumes, almost all contained compounds that damaged bacterial DNA, killed cells, blocked the hormone-making enzyme aromatase, or acted on human estrogen or androgen receptors in test organisms, regardless of price or whether the perfume was marketed to men or women.

Moderate evidence.

Source: Morlock & Heil 2025, Journal of Chromatography A Link to this fact

Health effects / Animal study

Two fragrance musks, AETT and musk ambrette, damaged the nervous system of rats in industry-sponsored studies and were withdrawn; musk ambrette was also barred from skin products because it caused allergic reactions in sunlight.

Moderate evidence.

Source: Ford 1994 (RIFM) Industry-funded Link to this fact

Health effects / Measured in people or real products

Sunlight can turn some fragrance chemicals into skin allergens: the now-banned perfume ingredient 7-methoxycoumarin made 11 of 25 volunteers photoallergic, and in people already sensitized, 0.001% plus UVA light triggered a reaction.

Moderate evidence: Artificial UVA at 20 J/cm2 (~1 h summer sun) for the 0.001% figure; predictive photomaximization test; ingredient banned in EU cosmetics since 2000.

Source: SCCNFP 2000 Link to this fact

Health effects / Lab study (cells or chemistry)

Two sunscreen ingredients, oxybenzone (benzophenone-3) and homosalate, blocked the male hormone receptor in human cells, at roughly the potency of the pesticide metabolite p,p'-DDE.

Moderate evidence.

Source: Schlumpf 2004, Toxicology Link to this fact

Health effects / Self-reported survey

In a national survey of 1,098 Australian adults, 6.5% said a doctor or health professional had told them they have multiple chemical sensitivities, and 18.9% said they are unusually sensitive to everyday chemicals.

Moderate evidence: Single self-reported 'ever told' item, online panel, adults 18-65; a South Australian population survey found 1% diagnosed; same dataset as the AU fragrance reports.

Source: Steinemann 2018, Preventive Medicine Reports Link to this fact

Health effects / Self-reported survey

Among Australians who said they had been diagnosed with multiple chemical sensitivities, 91.5% reported health problems from fragranced products such as air fresheners, scented cleaners, and other people's perfume.

Moderate evidence: N = 71; self-report; partly built into the definition.

Source: Steinemann 2018, Preventive Medicine Reports Link to this fact

Health effects / Self-reported survey

In a 2016 US national survey, 86% of people who said a doctor had diagnosed them with multiple chemical sensitivity reported health problems from fragranced products, most often breathing problems (50%), migraines (47%) and eye/nose symptoms (47%).

Moderate evidence: Self-report; 'diagnosed' = told by any health professional; opt-in online panel; same dataset as Steinemann 2016.

Source: Steinemann 2018 (JOEM), Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Self-reported survey

In the same 2016 US survey, about 1 in 4 adults (25.9%) said they were unusually sensitive to everyday chemicals such as cleaning products, perfume, and detergents, and 81% of them reported health problems from fragranced products.

Moderate evidence: Self-report; adults 18-65 in an opt-in online panel; earlier US telephone surveys gave 11-16%.

Source: Steinemann 2018 (JOEM), Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Measured in people or real products

Some people whose breathing problems are set off by scents do not have asthma or allergy: in a Swedish clinic study, 11 such patients had normal lung function, negative methacholine and allergy tests, and asthma medicines had given most of them little relief.

Moderate evidence: Clinic referrals selected for scent-triggered complaints; n=11; describes a phenotype, not its prevalence.

Source: Millqvist 1999, Allergy Link to this fact

Health effects / Measured in people or real products

In a small lab test where patients could not smell it, perfume released near their eyes caused more eye irritation than a saline dummy (1.1 vs 0.2 on a 0-3 scale); a later double-blind study found the same eye effect.

Moderate evidence: Single-blind, n=11, self-rated; corroborated double-blind by Elberling 2006 (8/21 patients vs 2/21 controls, P=0.07).

Source: Millqvist 1999, Allergy Link to this fact

Health effects / Review of other studies

A systematic review of workplace irritants found that people with pre-existing airway sensitivity (atopy plus non-specific bronchial hyper-responsiveness) can develop new-onset asthma from chronic, repeated exposure to an irritant at concentrations below the official occupational exposure limit.

Moderate evidence.

Source: Baur, Bakehe & Vellguth 2012, Journal of Occupational Medicine and Toxicology Link to this fact

Health effects / Measured in people or real products

In a small double-blind lab test, 12 people with multiple chemical sensitivity coughed significantly more than 12 healthy matched controls every time they inhaled capsaicin (the compound that makes chili peppers hot), and the difference grew larger at higher doses.

Moderate evidence: N=12 vs 12, single Gothenburg clinic, MCS diagnosed only by Cullen's clinical criteria (no independent biomarker), not independently replicated outside this research group.

Source: Ternesten-Hasséus 2002, Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Measured in people or real products

The extra coughing in multiple chemical sensitivity patients was not explained by asthma or classic allergy: patients tested negative on standard allergy skin-prick and methacholine airway-reactivity tests, and lung function (FEV1) did not change after capsaicin, pointing to an oversensitive airway nerve response rather than an allergic or asthmatic reaction.

Moderate evidence.

Source: Ternesten-Hasséus 2002, Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Measured in people or real products

In a nationally representative sample of 2,432 US women aged 20-49, women who douched frequently (2+ times/month) had 81% higher blood levels of 1,4-dichlorobenzene than women who never douched, with a dose-response trend across frequency categories (p=0.04).

Moderate evidence: Cross-sectional NHANES biomarker data; wide CI (2% to 221%); mothballs and toilet deodorizers are DCB's dominant known sources and could not be ruled out as confounders.

Source: Ding 2020, Journal of Women's Health Link to this fact

Health effects / Measured in people or real products

Using feminine powder in the past month was linked to 36% higher blood ethylbenzene in a nationally representative NHANES sample of reproductive-aged women.

Moderate evidence: Single VOC, modest effect size; alternative sources (e.g. talc packaging) not ruled out; no dose-response could be tested (frequency not collected).

Source: Ding 2020, Journal of Women's Health Link to this fact

Health effects / Measured in people or real products

Non-Hispanic Black women douched far more often than white women (39% vs 13% in the past month) and had significantly higher blood 1,4-dichlorobenzene, a possible contributor to racial differences in chemical exposure.

Moderate evidence: Association, not a demonstrated causal pathway; unadjusted racial comparison for the biomarker figure.

Source: Ding 2020, Journal of Women's Health Link to this fact

Health effects / Animal study

In a rat model of Parkinson's disease, oral citronellol (25 mg/kg/day) given as a month-long pretreatment before each day's dose of the neurotoxin rotenone reduced brain oxidative stress, inflammatory cytokines, glial activation, and the loss of dopamine-producing neurons.

Moderate evidence.

Source: Jayaraj 2022, Heliyon Link to this fact

Health effects / Measured in people or real products

Cleaning products were the suspected exposure in 236 of 1,915 (12%) confirmed work-related asthma cases across California, Massachusetts, Michigan, and New Jersey, 1993-1997; most were new-onset asthma (80%) and about a fifth were consistent with reactive airways dysfunction syndrome, an irritant-induced, non-allergic asthma type.

Moderate evidence.

Source: Rosenman 2003, Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Measured in people or real products

In California, janitors and cleaners had roughly double the confirmed work-related asthma rate of all other occupations combined (4.3 vs 2.3 per 100,000 workers).

Moderate evidence.

Source: Rosenman 2003, Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Self-reported survey

In a 1986 clinic and hospital survey of 60 asthma patients, 72% said perfume or cologne worsened their asthma, and two asthma patients who could not smell at all still reacted to perfume worn by others nearby.

Moderate evidence.

Source: Shim & Williams 1986, The American Journal of Medicine Link to this fact

Health effects / Self-reported survey

In a German cohort of 1,695 young adults (19-24) followed from childhood, frequent private use of household disinfectants (a composite of methods including hand-wash, machine, sponge, and spray disinfection) was associated with close to a threefold increase in the odds of newly developing asthma, compared with people who didn't use disinfectants (OR 2.79, 95% CI 1.14-6.83).

Moderate evidence.

Source: Weinmann 2017, Occupational and Environmental Medicine Link to this fact

Health effects / Animal study

AETT, a musk fragrance once common in soaps, deodorants, and cosmetics, caused progressive nerve-fiber demyelination and irreversible pigment build-up in the brains of rats fed the compound for 12-20 weeks; the fragrance industry voluntarily withdrew it from cosmetics in 1978 on the strength of its own data.

Moderate evidence: Small single-lab study (N=16 rats), one route (dietary), one dose pair (25/50 mg/kg/day); AETT was withdrawn from cosmetics in 1978 and is not a current fragrance ingredient.

Source: Spencer 1979, Science Industry-funded Link to this fact

Health effects / Measured in people or real products

The fragrance-linked phthalate DEP was found in 78% of the hair products tested, and cyclosiloxanes, parabens, and DEP were found at the highest concentrations, including one anti-frizz product that was 38-46% cyclosiloxane by weight.

Moderate evidence: N=18 products; concentration in the product is not the same as absorbed dose or exposure.

Source: Helm 2018, Environmental Research Link to this fact

Health effects / Measured in people or real products

Nitrate radicals alone, generated from ozone and nitrogen dioxide with no terpene present at all, raised human eye-blink frequency 21% — comparable in size to the effect of isoprene ozonolysis products — suggesting that some of the eye-irritating power of 'scented product plus ozone' indoor chemistry may come from reactive radicals in general, not from limonene specifically.

Moderate evidence.

Source: Klenø & Wolkoff 2004 Link to this fact

Health effects / Review of other studies

Odor and fragrance exposure reliably distracts people and slows some cognitive tasks (reaction time, lexical decisions), independent of any toxic effect.

Moderate evidence: Effect sizes are small and inconsistent across tasks, and persistence beyond a single exposure session is not established.

Source: Wolkoff & Nielsen 2017, Environment International Link to this fact

Health effects / Animal study

Mice breathing the vapor of one commercial solid air freshener for one hour showed dose-dependent airway irritation and, at higher doses, a ~35% fall in mid-expiratory airflow — the same magnitude reported for colognes in the same lab's companion study.

Moderate evidence.

Source: Anderson & Anderson 1997, Archives of Environmental Health Link to this fact

Health effects / Measured in people or real products

Using the identical question and instrument in the same Swedish town, adults report being bothered by strong odors about twice as often as teenagers (33% vs 15.6%), and objectively confirmed sensory hyperreactivity is about seven times more common in adults (6.3% vs 0.9%), suggesting chemical sensitivity often develops with age rather than being present from childhood.

Moderate evidence.

Source: Andersson 2008, International Journal of Hygiene and Environmental Health Link to this fact

Health effects / Lab study (cells or chemistry)

Three fragrance and cosmetic chemicals used in bodycare products applied around the breast — benzyl salicylate, benzyl benzoate, and butylphenylmethylpropional (Lilial) — activated the human estrogen receptor and increased growth of estrogen-dependent breast cancer cells in a laboratory dish, an effect blocked by an anti-estrogen drug, suggesting the mechanism runs through the estrogen receptor.

Moderate evidence.

Source: Charles & Darbre 2009, Journal of Applied Toxicology Link to this fact

Health effects / Lab study (cells or chemistry)

These estrogen-receptor effects only appeared at concentrations tens of thousands to millions of times higher than the natural hormone estradiol needs to produce the same size effect — this is laboratory-dish evidence that these chemicals can act like a weak estrogen, not evidence that normal skin or cosmetic use delivers enough of them to the breast to do so.

Moderate evidence.

Source: Charles & Darbre 2009, Journal of Applied Toxicology Link to this fact

Health effects / Measured in people or real products

In lab tests, basophils (a type of blood immune cell) from people with perfume-related breathing symptoms released significantly more histamine when exposed to strong perfume than basophils from healthy volunteers, but only at the strongest concentration tested; both groups' basophils started releasing histamine at the same dose.

Moderate evidence.

Source: Elberling 2007, Clinical and Experimental Allergy Link to this fact

Health effects / Measured in people or real products

The excess basophil reactivity to perfume in symptomatic patients was not explained by allergy antibodies in the blood (a passive-serum-transfer test found no difference between groups) and did not track whether a patient also had a skin (contact) allergy, an inhalant allergy, or asthma.

Moderate evidence.

Source: Elberling 2007, Clinical and Experimental Allergy Link to this fact

Health effects / Lab study (cells or chemistry)

In a laboratory study, triclosan exposed to UVB at an intensity matched to real midday sunlight in a subtropical city generated damaging free radicals and killed human skin cells (HaCaT keratinocytes) in a dose-dependent way.

Moderate evidence.

Source: Dubey 2019, Ecotoxicology and Environmental Safety Link to this fact

Health effects / Lab study (cells or chemistry)

Triclosan and UVB/sunlight together caused significant DNA damage (comet assay, micronuclei, cyclobutane pyrimidine dimers) in human skin cells in the laboratory, while triclosan alone in the dark and UVB/sunlight alone caused none.

Moderate evidence: Single in-vitro cell-line study; genotoxicity not shown in whole skin or in vivo.

Source: Dubey 2019, Ecotoxicology and Environmental Safety Link to this fact

Health effects / Measured in people or real products

In a 2021 audit of 50 stores across 8 Boston neighborhoods, stores in lower-income Roxbury and Mission Hill were more than twice as likely to stock a hair product with a high (7-10) Environmental Working Group hazard score than stores in higher-income, predominantly White Beacon Hill (risk ratio 2.3 for both).

Moderate evidence.

Source: Chan 2023, Environmental Health Perspectives Link to this fact

Health effects / Measured in people or real products

Hair relaxers were found for sale only in the lower-income, more racially diverse Boston neighborhoods studied; none were cataloged in the two highest-income/highest-White or Asian-share neighborhoods (Beacon Hill, Chinatown).

Moderate evidence.

Source: Chan 2023, Environmental Health Perspectives Link to this fact

Health effects / Measured in people or real products

In the best-controlled human test available, propylene glycol methyl ether (PGME) solvent vapor at 150 ppm produced no measurable objective eye damage (redness, corneal swelling, tear-film stability, blinking rate) when tested double-blind against a matched-odor placebo in 12 volunteers.

Moderate evidence: Small study (n=12, all male), single 2.5 h exposure; does not test longer or repeated exposures, other populations, or higher occupational concentrations.

Source: Emmen et al. 2003, Toxicology Letters Industry-funded Link to this fact

Health effects / Measured in people or real products

A statistically significant 'nose irritation' rating from a scented solvent vapor disappeared once how strongly subjects could smell the vapor was accounted for statistically, showing that self-reported irritation from a scented product can really be a report of smell, not tissue injury.

Moderate evidence: One study, one chemical, one nasal-irritation question; the eye-irritation rating in the same study did not similarly vanish.

Source: Emmen et al. 2003, Toxicology Letters Industry-funded Link to this fact

Health effects / Measured in people or real products

In a 3-hour chamber test at realistic ozone and citrus-terpene (limonene) levels, people with mild asthma rated the air as less irritating to their eyes, nose, and throat than healthy people did, but reported more chest tightness, headache, and flu-like symptoms.

Moderate evidence.

Source: Fadeyi et al. 2015, Indoor Air Link to this fact

Health effects / Measured in people or real products

People with mild asthma performed a concentration task significantly less accurately than healthy people during a 3-hour ozone-limonene chamber exposure, despite working faster.

Moderate evidence: Single study, no unexposed control arm, so it is not established that the chemistry (rather than general chamber occupancy or task load) caused the accuracy difference.

Source: Fadeyi et al. 2015, Indoor Air Link to this fact

Health effects / Measured in people or real products

In the nasal-lavage arm of the same 130-woman chamber study, breathing a VOC-ozone mixture containing citrus and pine scent chemicals (limonene, alpha-pinene) caused no significant increase in nasal irritation symptoms or in objective inflammation markers (immune cells, IL-6, IL-8, protein) in nasal fluid.

Moderate evidence.

Source: Laumbach 2005, Journal of Occupational and Environmental Medicine Link to this fact

Health effects / Review of other studies

General reviews of the skin-penetration literature put the size ceiling for crossing intact skin's outer barrier (the Stratum Corneum) at around 100 nanometers; larger particles usually do not cross it.

Moderate evidence: Stated as a citation to a prior review (Revel et al. 2018), not new primary data from this paper; an order-of-magnitude rule, not a precise cutoff.

Source: Menichetti et al. 2025, Journal of Xenobiotics Link to this fact

Health effects / Lab study (cells or chemistry)

When the outer skin barrier (Stratum Corneum) is removed or already compromised, far more 100-500 nanometer plastic nanoparticles get through than when it is intact, pointing to skin condition, not just particle size, as the deciding factor.

Moderate evidence.

Source: Menichetti et al. 2025, Journal of Xenobiotics Link to this fact

Health effects / Measured in people or real products

In a small Swedish clinic study, people whose breathing symptoms were set off by scents reacted to a blinded perfume challenge with more symptoms than a saline placebo, even though a nasal clamp meant they could not smell either one, and their lung function, oxygen levels, heart rate, and breathing rate never changed at all.

Moderate evidence: N=9, single clinic, self-rated symptoms, perfume-vs-saline contrast single-blind (not double-blind); no healthy control group.

Source: Millqvist & Löwhagen 1996, Allergy Link to this fact

Health effects / Measured in people or real products

Wearing a mask with an active-carbon filter, the kind designed to remove odors and organic vapors from the air, did not stop a scent-triggered breathing reaction to perfume: symptom scores with the carbon filter were no different from a dummy filter.

Moderate evidence.

Source: Millqvist & Löwhagen 1996, Allergy Link to this fact

Health effects / Measured in people or real products

In the clinical case series that first defined "irritable larynx syndrome," perfume was a named symptom trigger in about a quarter of patients (10 of 39), well behind reflux (72%) and other airborne irritants (51%).

Moderate evidence: Single specialist voice clinic, retrospective, uncontrolled, n=39; self-reported triggers, multiple allowed per patient; not an occupational or fragrance-specific population.

Source: Morrison 1999, Journal of Voice Link to this fact

Health effects / Measured in people or real products

About 85% of patients in the founding irritable larynx syndrome case series were judged to have gastroesophageal reflux contributing to their laryngeal symptoms, making reflux the single most common named trigger and etiologic factor, ahead of any airborne trigger including perfume.

Moderate evidence.

Source: Morrison 1999, Journal of Voice Link to this fact

Health effects / Measured in people or real products

In a small double-blind lab test, a drug that numbs sensory nerves (lidocaine) cut in half the number of coughs that chemically sensitive patients had after inhaling capsaicin, evidence that their airway sensitivity runs through nerve pathways rather than the kind of airway narrowing seen in asthma.

Moderate evidence.

Source: Millqvist 2000, Allergy Link to this fact

Health effects / Measured in people or real products

A blinded, controlled 30-minute lab exposure to two fragranced household aerosols caused no objective ocular redness or nasal congestion (acoustic rhinometry) change in mild or moderate asthmatics, and no drop in lung function (FEV1).

Moderate evidence.

Source: Opiekun 2003, Clinical and Experimental Allergy Industry-funded Link to this fact

Health effects / Measured in people or real products

Moderate asthmatics self-reported more nasal congestion after one of two fragranced aerosols, but objective nasal-airway measurement (acoustic rhinometry) on the same people at the same time found no change.

Moderate evidence.

Source: Opiekun 2003, Clinical and Experimental Allergy Industry-funded Link to this fact

Health effects / Review of other studies

Across 6 independent lab studies using a forced-choice 'which one is the real chemical?' test, people who report multiple chemical sensitivities were not better than other people at telling active chemical exposures apart from blank or sham ones.

Moderate evidence.

Source: Das-Munshi 2006, Journal of Allergy and Clinical Immunology Link to this fact

Health effects / Measured in people or real products

In one lab study of 180 people, simply telling them beforehand that an odor was an 'industrial solvent' (versus a 'relaxing natural extract' or a neutral label) made them report significantly more irritation and symptoms from the identical odorant, and the effect was strongest in people who normally rate odors as more reactive/irritating.

Moderate evidence: Reported via Das-Munshi's review, not read from the Dalton 1999 primary source directly; acquire Dalton 1999 (Health Psychol 18:579) to verify before treating as primary-grade.

Source: Das-Munshi 2006, citing Dalton 1999, Journal of Allergy and Clinical Immunology Link to this fact

Health effects / Self-reported survey

In a large random sample of Swedish adults (Vasterbotten, n=3,406), 12.2% said they get symptoms from odorous or pungent chemicals such as perfumes and cleaning agents in doses that don't bother most other people, but only 3.3% had actually been given a doctor's diagnosis of a chemical-intolerance condition.

Moderate evidence: Single region (Vasterbotten county), not national; diagnosis status is itself self-reported, not verified against medical records.

Source: Palmquist 2014, International Journal of Hygiene and Environmental Health Link to this fact

Health effects / Self-reported survey

People who report being intolerant to one environmental factor (chemicals, certain buildings, electromagnetic fields, or everyday sounds) are far more likely than chance to also report intolerance to another — for example, self-reported chemically intolerant Swedes were about six times more likely than average to also report building-related symptoms (observed 96 vs. 19.5 expected under chance).

Moderate evidence: Cross-sectional single-item design; cannot separate a shared physiological mechanism from a shared symptom-reporting/attribution style or shared exposure circumstances.

Source: Palmquist 2014, International Journal of Hygiene and Environmental Health Link to this fact

Health effects / Measured in people or real products

In a small case series, an Uber driver and four Uber passengers developed facial and eyelid airborne contact dermatitis linked to fragrance diffusers used inside the cars; all five patients had positive patch tests to fragrance mix I and/or balsam of Peru, and the driver's dermatitis improved after he removed his own diffuser.

Moderate evidence.

Source: Perper et al. 2017, Contact Dermatitis Link to this fact

Health effects / Measured in people or real products

In an unblinded human chamber study, 23 volunteers exposed to about 250 ppm propylene glycol monomethyl ether (PGME) vapor for 1-7 hours judged the odor objectionably unpleasant, and 20 of 23 developed eye irritation within about an hour, with some needing to leave early due to severe lacrimation; no subject at any tested concentration up to 2,050 ppm showed impaired vision, coordination, or reaction time.

Moderate evidence.

Source: Stewart 1970 (Arch Environ Health), Archives of Environmental Health: An International Journal Industry-funded Link to this fact

Health effects / Measured in people or real products

At 100 ppm PGME vapor, most of 6 subjects found the odor intolerable on first exposure, but odor tolerance developed within 25 minutes and all judged it mild; only 1-2 of the 6 reported mild or slight eye irritation over the following two hours, with no measurable effect on vision, coordination, or neurological tests.

Moderate evidence: Unblinded, n=6, no objective eye measurements; a double-blind study at the same concentration (Emmen 2003) found no eye effects at all, subjective or objective.

Source: Stewart 1970 (Arch Environ Health), Archives of Environmental Health: An International Journal Industry-funded Link to this fact

Health effects / Self-reported survey

In a nationally representative German survey, one in five adults (19.9%) report at least one health effect from fragranced products, and more than half of them (55.3%) report respiratory problems, not skin problems — the focus of most prior German fragrance research.

Moderate evidence: Self-report; no clinical confirmation; n=1,102, Germany 2019; same dataset as Klaschka 2020b.

Source: Klaschka 2020a, Environmental Sciences Europe Link to this fact

Health effects / Self-reported survey

People who already blame fragrances for their own symptoms do not use less of them: 98.6% of Germany's fragrance-sensitive survey respondents are still exposed to fragrances from their own weekly use, slightly above the general population's 96.9%.

Moderate evidence: Self-report; cannot rule out that affected people simply notice or report their own exposure more accurately rather than actually using more.

Source: Klaschka 2020a, Environmental Sciences Europe Link to this fact

Health effects / Self-reported survey

Among adults with a diagnosis of autism or autism spectrum disorder, 71.4% (US) and 51.2% (Australia) report health problems from the scent of laundry products coming from a dryer vent — the highest prevalence of any group measured (general population, asthmatics, autistic adults, migraineurs) in either country.

Moderate evidence.

Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact

Health effects / Self-reported survey

Among people who get migraines, 40.8% (US) and 29.1% (Australia) report health problems from the scent of laundry products coming from a dryer vent, with asthma attacks the most frequently reported effect in this group.

Moderate evidence.

Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact

Health effects / Review of other studies

Quaternary ammonium compounds such as benzalkonium chloride (BAC) and didecyldimethylammonium chloride (DDAC) have been linked to occupational asthma, contact dermatitis, and urticaria in healthcare workers, professional cleaners, and hairdressers with heavy, repeated exposure to disinfectants, antiseptics, and cosmetic preservatives.

Moderate evidence.

Source: Peyneau 2022, Frontiers in Toxicology Link to this fact

Health effects / Other evidence

In mice, repeated exposure to a specific odorant made the sense of smell more sensitive to that exact odorant, and the change arose at least partly in the smell-sensing tissue of the nose (the olfactory epithelium), not only in the brain.

Moderate evidence.

Source: Yee & Wysocki 2001, Physiol Behav 72:705-711, Physiology & Behavior Link to this fact

Health effects / Other evidence

In mice, odor detection thresholds were not fixed: 10 days of exposure to one odorant sharpened detection of that odorant 3- to 20-fold without changing sensitivity to an unexposed odorant.

Moderate evidence.

Source: Yee & Wysocki 2001, Physiol Behav 72:705-711, Physiology & Behavior Link to this fact

Health effects / Measured in people or real products

In a lab EEG study, people who scored high on a validated chemical-sensitivity questionnaire showed brainwave (ERP) evidence of difficulty disengaging attention from a pungent gas (CO2) and an odorant (amyl acetate) specifically, not from a neutral tone, when told to ignore them and focus on another task.

Moderate evidence.

Source: Andersson 2009, Journal of Psychosomatic Research Link to this fact

Health effects / Measured in people or real products

The same chemically sensitive group did not habituate to repeated chemical exposure over 1.5 hours (perceived intensity of CO2 and an ERP amplitude marker stayed flat), while a nonsensitive comparison group habituated normally on both measures.

Moderate evidence.

Source: Andersson 2009, Journal of Psychosomatic Research Link to this fact

Health effects / Review of other studies

In human nasal provocation studies, hypertonic saline triggers substance P release within the first 3 minutes and dose-dependent glandular mucus secretion over the following 3-5 minutes, but produces no measurable increase in nasal-lavage albumin (a marker of vascular permeability) — a pattern reproduced in normal volunteers, acute allergic rhinitis, and acute and chronic rhinosinusitis patients.

Moderate evidence: This review summarizes the authors' own earlier provocation trials rather than presenting independent replication; sample sizes and statistics are not restated in this review.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Other evidence

The human nasal 'axon response' that follows hypertonic saline provocation drives glandular secretion but, unlike neurogenic inflammation described in rat trachea and other rodents, produces no vascular-permeability (plasma leak) component in human nasal mucosa — a stated species dissociation between rodent and human neurogenic inflammation.

Moderate evidence.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Other evidence

Histamine nasal provocation produces itch, increased vascular permeability, and cholinergic reflex-driven glandular secretion (the classic allergic-rhinoconjunctivitis pattern), but histamine-induced 'axon responses' — direct local neuropeptide release from sensory nerve terminals — have not been clearly demonstrated in human airway mucosa.

Moderate evidence: This is an absence-of-evidence statement from a narrative review; the authors do not report having done a systematic search for such studies.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Review of other studies

A family of temperature- and chemical-gated TRP ion channels spans the range of stimuli relevant to breathing: TRPV2 detects tissue-damaging heat (>=52C), TRPV1 detects warmth/capsaicin/low pH/ethanol (>=42C), TRPV3/TRPV4 detect normal ambient temperature and osmotic/mechanical changes (roughly 22-40C), TRPM8 detects menthol and cool temperatures (8-22C), and TRPA1 detects very cold temperatures, mustard oil, garlic isothiocyanates, and THC (below 8C) but not menthol.

Moderate evidence: This is a conceptual/diagrammatic synthesis of previously published receptor characterization studies, not new data generated in this paper.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Review of other studies

TRPV1 is expressed well beyond nociceptive nerves, including on airway, skin, gastrointestinal, bladder, and rectal epithelial cells, plus the substantia nigra, hippocampus, and hypothalamus — meaning capsaicin and other TRPV1 ligands can act directly on epithelium without involving nerves at all.

Moderate evidence: Synthesized from cited prior localization studies, not measured in this paper.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Review of other studies

Cold, dry air causes dose-dependent nasal airflow obstruction in people with idiopathic nonallergic rhinitis but not in healthy controls, while separately, low-dose chlorine that produces no perceptible sensory irritation can still cause neurogenic nasal airflow obstruction with no detectable neuropeptide release — pointing to a non-classical, local mucosal mechanism distinct from typical axon-response neurogenic inflammation.

Moderate evidence.

Source: Baraniuk & Merck 2009, Annals of the New York Academy of Sciences Link to this fact

Health effects / Review of other studies

A systematic review of 27 human chemical-exposure challenge studies on multiple chemical sensitivity (1998-2015) found no scientific consensus on whether the reaction is physical (toxicological) or psychological: only a minority of studies concluded toxicological causation, a similar minority concluded psychological causation, and the single largest group of studies reached no conclusion at all.

Moderate evidence.

Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact

Health effects / Self-reported survey

Among 129 clinically diagnosed MCS patients in Rome, hyperosmia and asthenia were the most common symptoms (about 97% and 83% of patients) and clustered together statistically, followed by respiratory symptoms (dyspnea, cough, tachypnea; about 72%) and neurocognitive symptoms (confusion, attention/memory/decision-making deficits; about 62%).

Moderate evidence: Single-center clinical (not population) sample of physician-diagnosed patients; no control group; no exposure measurement; describes symptom co-occurrence, not cause.

Source: Del Casale 2020 Link to this fact

Health effects / Review of other studies

Across 13 independent qualitative studies from four countries, people with multiple chemical sensitivity consistently describe being kept out of everyday places by scented/chemical products, and losing jobs, income, or social relationships because of it.

Moderate evidence.

Source: Driesen 2020, Journal of Psychosomatic Research Link to this fact

Health effects / Measured in people or real products

In a controlled study of 7 asthmatic subjects, 0.5 ppm sulfur dioxide alone and cold, dry air alone each caused no significant airway narrowing, but breathing the two together raised specific airway resistance more than 3-fold (6.94 to 22.35 l*cmH2O*l-1*s, P<0.001), with worsened wheeze or breathlessness in 6 of 7 subjects.

Moderate evidence.

Source: Bethel 1984 Link to this fact

Health effects / Measured in people or real products

In asthmatic subjects, self-rated shortness-of-breath severity correlated only loosely with objectively measured airway resistance after inhaling irritant stimuli; the categories overlapped so much that a person's own symptom report gave little information about how much bronchoconstriction had actually occurred.

Moderate evidence: Small study (n=7), single ordinal symptom scale; consistent with our broader point that self-reported symptom severity and objective physiological response are different measures.

Source: Bethel 1984 Link to this fact

Health effects / Measured in people or real products

In a controlled chamber study of 85 volunteers, people with mild asthma and people with moderate/severe (medication-dependent) asthma showed similar increases in airway narrowing and symptoms per increment of sulfur dioxide exposure (0.2-0.6 ppm); clinical asthma severity did not reliably predict who reacted most to the gas itself, though moderate/severe asthmatics had a higher baseline (clean-air) symptom and airway-resistance level.

Moderate evidence.

Source: Linn et al. 1987, American Review of Respiratory Disease Link to this fact

Health effects / Measured in people or real products

An individual's sensitivity to a given dose of an irritant gas (sulfur dioxide) was highly reproducible when the same person was retested 1-7 weeks later (r=0.85 across all subjects, r=0.82-0.74 within asthmatic subgroups), even though that sensitivity could not be predicted well from a clinical asthma diagnosis, allergy skin testing, or serum IgE level.

Moderate evidence: Single-lab study, n=85 total; reproducibility was much weaker for exercise responses measured in clean air alone.

Source: Linn et al. 1987, American Review of Respiratory Disease Link to this fact

Health effects / Measured in people or real products

Atopic (allergic, IgE-sensitized) volunteers without asthma were essentially as unresponsive to sulfur dioxide exposure as non-atopic normal volunteers; airway hyperreactivity (asthma), not IgE-mediated allergy/atopy, was what predicted reaction to this irritant gas.

Moderate evidence.

Source: Linn et al. 1987, American Review of Respiratory Disease Link to this fact

Health effects / Test-chamber measurement

Telling people a real chemical exposure is a harmful industrial solvent versus a beneficial natural extract changed how irritating they rated identical 800 ppm acetone air and how many health symptoms (throat/nasal irritation, lightheadedness, nausea, drowsiness) they reported afterward, even though every group breathed the same concentration.

Moderate evidence: Single lab, single cohort, not independently replicated; co-funded by the Chemical Manufacturers' Association alongside NIH grants (coi/industry-funded).

Source: Dalton et al. 1997, Int Arch Occup Environ Health 69:407-417 Industry-funded Link to this fact

Health effects / Other evidence

Objective, blinded odor-detection thresholds for acetone and butanol did not differ between subjects given positive, negative, or neutral framing of the same acetone exposure, even though their subjective irritation and symptom ratings differed sharply by framing.

Moderate evidence: Single lab, single cohort; thresholds tested olfactory (CN I) sensitivity only, not trigeminal chemesthesis.

Source: Dalton et al. 1997, Int Arch Occup Environ Health 69:407-417 Industry-funded Link to this fact

Health effects / Measured in people or real products

In a small Swedish clinic study, people whose breathing symptoms were triggered by scents and chemical irritants — but who had normal lung function and negative allergy and asthma tests — coughed much more after inhaling capsaicin (the hot-pepper compound) than either people with verified asthma or healthy volunteers (93 vs 23 average coughs at the highest dose, P<0.001).

Moderate evidence.

Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact

Health effects / Measured in people or real products

The extra coughing in these chemically sensitive patients could not be explained by asthma: their lung function, methacholine reactivity, and skin-prick allergy testing were all normal, yet they still coughed dose-dependently to inhaled capsaicin, and even to a plain saline control, while a separate group of people with verified asthma did not cough more than healthy volunteers.

Moderate evidence.

Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact

Health effects / Government agency

As of 1998, EPA's own environmental-health office stated that certain types of childhood cancer were increasing but the causes were largely unknown, and that the agency lacked a reliable basis to determine whether most untested high-production-volume industrial chemicals were safe or unsafe for children.

Moderate evidence.

Source: Goldman 1998, Environmental Health Perspectives Link to this fact

Health effects / Self-reported survey

People with asthma were about 4 times more likely to report a doctor's diagnosis of environmental illness/multiple chemical sensitivity than people without asthma (19.0% vs. 4.6%), and over twice as likely to self-report unusual sensitivity to everyday chemicals (31.5% vs. 13.9%).

Moderate evidence.

Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact

Health effects / Self-reported survey

Women were about 1.6 times more likely than men to self-report sensitivity to more than one everyday chemical, after adjusting for other factors, though doctor-diagnosed MCS itself was not significantly associated with sex.

Moderate evidence.

Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact

Health effects / Self-reported survey

Reports of doctor-diagnosed multiple chemical sensitivity and self-reported chemical sensitivity were spread fairly evenly across race/ethnicity, income, education, marital status, and geography in a representative California sample, unlike clinic-based case series which have reported a predominance of middle- to upper-class white women.

Moderate evidence.

Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact

Health effects / Measured in people or real products

In healthy volunteers using an oxymetazoline nasal decongestant spray for 30 days, adding the preservative benzalkonium chloride (BKC) produced significantly greater rebound nasal mucosal swelling (P < 0.01) and evening nasal stuffiness (P < 0.05, from week 2 onward) than the same spray without BKC.

Moderate evidence.

Source: Graf 1999, Clinical Therapeutics Industry-funded Link to this fact

Health effects / Measured in people or real products

In a 3-arm trial, benzalkonium chloride (BKC) alone (no decongestant) produced significantly more nasal mucosal swelling than placebo after 30 days, but did not cause subjective nasal stuffiness; oxymetazoline alone caused pronounced nasal hyperreactivity to histamine challenge and subjective stuffiness, suggesting the two agents contribute distinct, additive components to rhinitis medicamentosa.

Moderate evidence: N=10/arm, healthy volunteers, single research group.

Source: Graf 1999, Clinical Therapeutics Industry-funded Link to this fact

Health effects / Other evidence

In a standard mouse bioassay, methacrolein is primarily an upper-airway (sensory) irritant: it caused a concentration-dependent drop in breathing rate at 2-26 ppm (RD50 = 10.4 ppm) with no detectable pulmonary irritation or desensitization over 30 minutes of exposure.

Moderate evidence: Single small study (n=4 mice per concentration), one lab, acute exposure only (30 min); no chronic or repeated-exposure data.

Source: Larsen & Nielsen 2000, Toxicology Letters Industry-funded Link to this fact

Health effects / Other evidence

Methacrolein activates the sensory-irritant receptor by chemically reacting with it (like acrolein), not by simple physical adsorption, and its carbon-carbon double bond — not its aldehyde group — is the key reactive feature; it is roughly six times less potent than acrolein itself.

Moderate evidence: Mechanistic inference from a potency-ratio comparison across compounds tested in different (cited) studies, not a direct receptor-binding assay.

Source: Larsen & Nielsen 2000, Toxicology Letters Industry-funded Link to this fact

Health effects / Animal study

In a mouse inhalation screening study, all five commercial fabric-softener dryer pads tested (three scented, two labeled unscented) caused significant sensory irritation (21-58% of breaths) and airflow limitation (6-32%) compared to sham exposure, and two of the five brands also caused significant pulmonary irritation (12% and 23%); the two 'unscented'-labeled brands were just as irritating as the scented ones.

Moderate evidence.

Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact

Health effects / Animal study

In the same study, a cotton tee-shirt that had already been dried with a fabric-softener pad — not the pad itself — still emitted enough residual chemical to cause significant sensory irritation in mice (49% of breaths, versus 6% for an unwashed new shirt), at a much lower bulk air concentration (86 ppm) than the raw pad's headspace.

Moderate evidence.

Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact

Health effects / Other evidence

Despite reporting more symptoms at higher VOC concentrations, the same subjects showed no significant change in lung function (FEV1, FVC) or in nasal-lavage and induced-sputum cell counts and inflammatory markers (neutrophils, IL-8, LTB4, albumin) at 25 or 50 mg/m3.

Moderate evidence.

Source: Pappas et al. 2000, Int J Occup Environ Health 6:1-8 Link to this fact

Health effects / Other evidence

This chamber study directly conflicts with an earlier study (Koren et al. 1992) on the same measurement: Koren found more neutrophils in nasal-lavage fluid after a similar VOC mixture at 25 mg/m3, while this study found no nasal-lavage neutrophil increase at 25 or 50 mg/m3 in the full sample.

Moderate evidence.

Source: Pappas et al. 2000, Int J Occup Environ Health 6:1-8 Link to this fact

Health effects / Lab study (cells or chemistry)

In a lab test, four common fragrance/flavor chemicals found in essential oils – citral, geraniol, nerol, and trans-anethole – weakly activated the human estrogen receptor, and eugenol weakly blocked it, but all needed concentrations 100,000 to 1,000,000 times higher than the body's own estrogen to show any effect.

Moderate evidence: Single-lab yeast reporter assay, confirmed by direct receptor-binding but not by a second cell-based assay (Ishikawa cells, negative for all compounds).

Source: Howes et al. 2002, Journal of Pharmacy and Pharmacology Link to this fact

Health effects / Animal study

When the two most estrogen-receptor-active compounds, citral and geraniol, were applied to the skin of mice at doses about 6,000 times the effective estrogen dose, neither produced any of the classic signs of estrogen exposure (uterus growth or increased uterine blood-vessel leakiness).

Moderate evidence: N=5-6 mice per group, one species, one route (transdermal), short exposure (single dose or 3 days).

Source: Howes et al. 2002, Journal of Pharmacy and Pharmacology Link to this fact

Health effects / Lab study (cells or chemistry)

Linalool and eucalyptol (1,8-cineole) – two of the main scent chemicals in lavender and tea tree oil – showed no estrogen-receptor activity at all in this yeast test, alongside 14 other common essential-oil constituents that were tested and found inactive.

Moderate evidence.

Source: Howes et al. 2002, Journal of Pharmacy and Pharmacology Link to this fact

Health effects / Review of other studies

Three large NEI-sponsored trials (OHTS, EMGT, BISED) each found an increased incidence of cataract or nuclear lens opacity in patients on long-term topical antiglaucoma medication compared with untreated or lower-IOP patients, but none was designed to identify a cause.

Moderate evidence.

Source: Brandt 2003 (editorial), Archives of Ophthalmology Industry-funded Link to this fact

Health effects / Self-reported survey

In a 2002-03 US national telephone survey of 1,054 randomly selected adults, 11.2% self-identified as unusually sensitive to everyday chemicals such as cleaning products, perfume, and detergents, and 2.5% said they had been medically diagnosed with multiple chemical sensitivity (MCS).

Moderate evidence.

Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact

Health effects / Self-reported survey

In the same national survey, almost 1 in 3 adults (31.1%) said being next to someone wearing a scented product was irritating, and about 1 in 6 (17.6%) said air fresheners gave them headaches, breathing difficulties, or other health problems.

Moderate evidence: Self-report, single national telephone survey; 46.3% found scented products on others appealing rather than irritating.

Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact

Health effects / Self-reported survey

Among the 11.2% of US adults who self-identified as chemically hypersensitive, about 2 in 3 (66.7%) described their symptoms as severe or moderately severe, and about 1 in 7 (13.2%) said they had lost a job because of it; 72.7% had changed their household or personal-care products.

Moderate evidence: Self-report severity and lifestyle-effect items in a subgroup of n=117-122; no clinical verification.

Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact

Health effects / Self-reported survey

In this national survey, women were reported as chemically hypersensitive at roughly 4 times the rate of men (about 15.9% of women vs 4.0% of men, wiki arithmetic from the paper's cross-tabulation), and prevalence rose steadily with age from about 7% under age 36 to about 15% over age 50.

Moderate evidence.

Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact

Health effects / Self-reported survey

In the ALSPAC cohort, mothers who used air fresheners daily or on most days during pregnancy more often reported depression (adjusted OR 1.19) and headache or migraine (adjusted OR 1.24) 8 months after giving birth; aerosol use was similarly associated with headache (adjusted OR 1.25) but not depression.

Moderate evidence.

Source: Farrow 2003, Archives of Environmental Health: An International Journal Link to this fact

Health effects / Self-reported survey

In a 1999-2000 telephone survey of 1,582 randomly selected adults in the Atlanta, Georgia metro area, 12.6% self-identified as unusually sensitive to everyday chemicals, and 3.1% reported a medical diagnosis of environmental illness or multiple chemical sensitivity (MCS).

Moderate evidence: Single regional random-digit-dial telephone survey; self-report with no clinical verification of hypersensitivity or diagnosis.

Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact

Health effects / Self-reported survey

Among Atlanta-area adults who reported chemical hypersensitivity, about 1 in 7 (13.5%) said they had lost a job because of it (1.8% of the entire sample), and about 3 in 10 (29.9%) said it made shopping in stores difficult.

Moderate evidence: Self-report, single regional survey; asked only of the 199 respondents who reported hypersensitivity.

Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact

Health effects / Self-reported survey

In this Atlanta sample, women were reported as chemically hypersensitive at roughly 1.75 times the rate of men (about 15.7% of women vs 8.95% of men, wiki arithmetic from the paper's cross-tabulation), a smaller sex skew than the same authors' national survey found (F:M about 4.0).

Moderate evidence: Sex-specific prevalence rates are evidence base arithmetic from the paper's Table 4 cross-tabulation, not stated directly by the authors; single regional self-report survey.

Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact

Health effects / Self-reported survey

In the same follow-up, the most common symptoms reported after a chemical exposure were headache (88.4%) and burning eyes (76.8%), followed by asthma-like breathing difficulty (59.4%) and nausea or stomach distress (55.1%).

Moderate evidence.

Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact

Health effects / Self-reported survey

In a 10-country European cohort of 3,503 adults who did the cleaning at home and were asthma-free at baseline, using household cleaning sprays at least once a week was associated with a 49% higher rate of new asthma symptoms or asthma-medication use over about 9 years of follow-up.

Moderate evidence: Single multinational cohort (not yet independently replicated by a different research group); exposure and symptom outcomes were both self-reported at one follow-up interview.

Source: Zock et al. 2007, American Journal of Respiratory and Critical Care Medicine Link to this fact

Health effects / Self-reported survey

Using household cleaning sprays at least 4 days a week was linked to roughly double the rate of new physician-diagnosed asthma (HR 2.11, 95% CI 1.15-3.89) compared with light or no spray use, with a clear dose-response across frequency categories (P for trend 0.041) and number of different sprays used (P for trend 0.022).

Moderate evidence: Physician-diagnosed asthma relied on participant report of a doctor's diagnosis, not independent verification; single cohort.

Source: Zock et al. 2007, American Journal of Respiratory and Critical Care Medicine Link to this fact

Health effects / Self-reported survey

Cleaning products that were not applied as a spray (liquid multiuse cleaners, washing powders, polishes, bleach, ammonia, decalcifiers) showed no significant association with new-onset asthma in this study, while glass-cleaning, furniture, and air-refreshing sprays did.

Moderate evidence.

Source: Zock et al. 2007, American Journal of Respiratory and Critical Care Medicine Link to this fact

Health effects / Self-reported survey

The household-spray-asthma association was not modified by atopy (allergic sensitization): risk was similar in atopic (RR 1.30) and non-atopic (RR 1.33) participants, supporting an irritant rather than allergic mechanism.

Moderate evidence: Single cohort; the study could not directly test cellular/immunological mechanism, only the atopy-stratified association.

Source: Zock et al. 2007, American Journal of Respiratory and Critical Care Medicine Link to this fact

Health effects / Measured in people or real products

In a PET brain-imaging study of 12 women with multiple chemical sensitivity (MCS) and 12 matched controls, MCS subjects activated the brain's core odor-processing regions (amygdala, piriform, and insular cortex) LESS than controls when smelling most odorants, not more, despite resting brain activity being normal in both groups.

Moderate evidence: N=12/group, women only, single center (Karolinska), no independent replication of this exact PET paradigm in our evidence base yet.

Source: Hillert et al. 2007, Human Brain Mapping Link to this fact

Health effects / Measured in people or real products

The same MCS subjects showed extra activation of the anterior cingulate cortex and cuneus-precuneus during odor smelling that was not seen in controls, a pattern the authors call 'highly speculative' evidence for top-down (brain-level) regulation of odor response rather than a sensitized peripheral or olfactory system.

Moderate evidence: The authors themselves label the top-down/harm-avoidance explanation highly speculative; it is one candidate account among several, not established mechanism.

Source: Hillert et al. 2007, Human Brain Mapping Link to this fact

Health effects / Measured in people or real products

MCS subjects showed real, measurable physical changes during odor exposure that controls did not: their heart rate rose (RR interval fell, P<0.0001) and their breathing pattern changed differently from controls specifically while smelling odorants (not odorless air), a difference that held up even after statistically controlling for breathing pattern itself.

Moderate evidence: N=12/group; the finding shows odor-locked autonomic distress, not that the distress is caused by a specific chemical mechanism.

Source: Hillert et al. 2007, Human Brain Mapping Link to this fact

Health effects / Measured in people or real products

Odor detection thresholds (n-butanol test) did not differ between MCS subjects and controls (P=0.8), and nasal anatomy was normal in both groups, so normal ability to smell coexisted with abnormal brain and autonomic responses to odors.

Moderate evidence: Tests only the olfactory (CN I) channel; says nothing about the trigeminal/chemesthetic channel some MCS mechanism hypotheses focus on.

Source: Hillert et al. 2007, Human Brain Mapping Link to this fact

Health effects / Measured in people or real products

In a double-blind chamber study of 130 healthy women, those who scored high on a validated chemical-odor-intolerance questionnaire did not have worse symptoms, stress-hormone (cortisol) levels, or cognitive/driving-simulation performance when exposed to an indoor VOC or VOC-plus-ozone mixture, compared to women who scored low on the same questionnaire.

Moderate evidence.

Source: Fiedler 2008, Psychosomatic Medicine Link to this fact

Health effects / Measured in people or real products

Women prone to negative affect (anxiety, worry, distress) became more anxious after a public-speaking stressor during an indoor-chemical exposure session, regardless of what was in the air (clean air, VOCs, or VOCs plus ozone) – but they did not show higher cortisol or more physical (non-anxiety) symptoms than women low in negative affect.

Moderate evidence.

Source: Fiedler 2008, Psychosomatic Medicine Link to this fact

Health effects / Measured in people or real products

People who scored high in chemical intolerance or negative affect rated the same chemical exposure and their own symptoms as more annoying and more distressing than other participants did, even though their measured symptom counts, cortisol, and driving/attention performance were no different.

Moderate evidence: Annoyance/distress were retrospective, subjective 5-point ratings, not the same structured symptom-severity measure used for the main null; single study, healthy women only.

Source: Fiedler 2008, Psychosomatic Medicine Link to this fact

Health effects / Other evidence

In a large Canadian population survey, more frequent use of personal care products was associated with small but statistically significant reductions in objectively measured lung function.

Moderate evidence: Single cross-sectional study; exposure was self-reported, not measured; cannot establish causation.

Source: Dales 2013, Annals of Epidemiology Link to this fact

Health effects / Other evidence

In both men and women, more frequent use of hairstyle products (hairspray, gel, mousse) was associated with an approximate 2% decrease in FEV1, FVC, and the FEV1/FVC ratio.

Moderate evidence: Self-reported frequency of use, not measured exposure; no specific chemical or product identified as responsible.

Source: Dales 2013, Annals of Epidemiology Link to this fact

Health effects / Other evidence

Restricting the analysis to never-smokers did not remove the association between personal care product use and lower lung function in women.

Moderate evidence: Subgroup analysis of a single cross-sectional cohort; wide confidence intervals.

Source: Dales 2013, Annals of Epidemiology Link to this fact

Health effects / Self-reported survey

Among 543 healthcare workers in 7 French hospitals/clinics, occupational exposure to quaternary ammonium compounds (QACs, e.g. benzalkonium chloride) was linked to about 7.5x higher odds of reported physician-diagnosed asthma (adjusted OR 7.56, 95% CI 1.84-31.05) and about 3.2x higher odds of nasal symptoms at work (adjusted OR 3.21, 95% CI 1.42-7.22), after adjustment for age, gender, smoking, BMI, and atopy.

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Health effects / Self-reported survey

In the same study, chlorine/bleach exposure (adjusted OR 1.01, 95% CI 0.47-2.18), latex glove use (adjusted OR 0.69, 95% CI 0.32-1.51), and glutaraldehyde exposure (crude OR 1.31, 95% CI 0.53-3.23) showed no significant association with reported asthma; QAC exposure was the only occupational chemical exposure that remained statistically significant after adjustment.

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Health effects / Self-reported survey

The single highest-risk activity for asthma and nasal symptoms was manual dilution of concentrated disinfectant products (adjusted OR 4.01, 95% CI 1.34-12.00 for asthma; 1.90, 95% CI 1.13-3.18 for nasal symptoms), higher than general disinfection or cleaning tasks alone.

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Health effects / Measured in people or real products

Only 6.5% of tested healthcare workers (32 of 494) had detectable specific IgE antibodies to quaternary ammonium compounds, and this was not significantly associated with reported asthma, new-onset asthma, or nasal symptoms — despite QAC exposure itself being strongly associated with those same outcomes. The study authors read this pattern as pointing to an irritant, not an IgE-mediated allergic, mechanism.

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Health effects / Self-reported survey

Reported physician-diagnosed asthma prevalence varied sharply by healthcare occupation: 16.1% among nurses, 16.7% among auxiliary nurses, 7.7% among cleaners, 5.1% among other healthcare workers, and 3.4% among administrative staff (overall 11.2%, p=0.003).

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Health effects / Review of other studies

Benzalkonium chloride (BAK), the preservative in most glaucoma eye drops, accumulates in the trabecular meshwork and other deep ocular tissues after chronic topical use and has a tissue half-life of about 20 hours in the corneal/conjunctival epithelium.

Moderate evidence: Accumulation is well documented; a causal link between that accumulation and disease progression is not established by these detection studies alone.

Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact

Health effects / Other evidence

BAK-exposed trabecular meshwork tissue and cells share the same qualitative cellular and molecular damage signature — cell loss, apoptosis, increased reactive oxygen species, extracellular matrix accumulation, decreased outflow, fibronectin upregulation, and cellular senescence — seen in the trabecular meshwork of primary open-angle glaucoma patients.

Moderate evidence.

Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact

Health effects / Measured in people or real products

Burning candles indoors measurably shifted a marker of heart-rhythm regulation (heart rate variability) toward a more 'rest and digest' pattern within about 30-90 minutes, in a chamber study using candle-smoke levels similar to real dinner-table use.

Moderate evidence: Single small (n=22) study, one lab; heart rate itself did not change; the effect (HF-HRV +22.3%, p=0.01 vs. clean air) is not yet independently replicated.

Source: Hagerman et al. 2014, Atmospheric Environment Link to this fact

Health effects / Other evidence

In a controlled bronchoprovocation study of 28 adults with mild, stable asthma, doubling doses of inhaled benzalkonium chloride (BAC) produced bronchospasm (at least 20% FEV1 fall) in 17 of 28 subjects (61%, mean FEV1 decrease 28%), with a cumulative threshold dose of about 300 micrograms (1.00 micromole); pretreatment with the mast-cell stabilizer cromolyn, but not ipratropium, blocked the response.

Moderate evidence: Single study, small sample (28 subjects), adults with mild/stable (not severe) asthma; not a systematic review or meta-analysis.

Source: Prabhakaran 2017 Link to this fact

Health effects / Other evidence

In a double-blind randomized crossover study of 18 young adults with stable asthma, repeated 600-microgram doses of benzalkonium chloride (up to 4 doses, 20 minutes apart) produced a mean 17% fall in FEV1, versus no significant difference between EDTA and placebo; 6 of 18 subjects had an FEV1 fall of more than 20%.

Moderate evidence: Small sample (18 subjects), single study; EDTA and BAC are both nebulizer-solution additives but were tested for different purposes.

Source: Prabhakaran 2017 Link to this fact

Health effects / Other evidence

A randomized double-blind study of a single, clinically realistic dose of albuterol with benzalkonium chloride (100 micrograms BAC plus 2.5 mg albuterol) found no decrease in bronchodilator response compared with preservative-free albuterol in 22 adults with mild stable asthma.

Moderate evidence.

Source: Prabhakaran 2017 Link to this fact

Health effects / Self-reported survey

In a cohort of 4,102 US nurses already diagnosed with asthma (Nurses' Health Study II), weekly use of disinfectants to clean medical instruments was associated with poorly controlled asthma (OR 1.37, 95% CI 1.05-1.79) and very poorly controlled asthma (OR 1.88, 95% CI 1.38-2.56) versus no weekly instrument disinfection, after adjusting for age, smoking, BMI, race and ethnicity.

Moderate evidence.

Source: Dumas 2017, European Respiratory Journal Link to this fact

Health effects / Self-reported survey

Weekly use of disinfectant/cleaning sprays at work was associated with worse asthma control in US nurses (OR 1.50, 95% CI 1.16-1.94 for poorly controlled; OR 1.38, 95% CI 1.00-1.92 for very poorly controlled), and the association held even among nurses who used sprays less than once a week.

Moderate evidence.

Source: Dumas 2017, European Respiratory Journal Link to this fact

Health effects / Self-reported survey

Using an expert job-task-exposure matrix, high occupational exposure to formaldehyde (OR 1.33), glutaraldehyde (OR 1.18), hypochlorite bleach (OR 1.18), hydrogen peroxide (OR 1.19) and enzymatic cleaners (OR 1.33, the only one significant at P<0.001) was each associated with poorer asthma control in US nurses, versus low exposure to the same chemical.

Moderate evidence.

Source: Dumas 2017, European Respiratory Journal Link to this fact

Health effects / Self-reported survey

US nurses exposed to a combination of aldehydes (formaldehyde or glutaraldehyde) plus hypochlorite bleach/hydrogen peroxide plus enzymatic cleaners had the strongest asthma-control signal in the study: odds ratio 1.91 (95% CI 1.31-2.79) for very poorly controlled asthma versus nurses with low exposure to all seven disinfectant categories studied (P-trend=0.001).

Moderate evidence.

Source: Dumas 2017, European Respiratory Journal Link to this fact

Health effects / Self-reported survey

Occupational exposure to quaternary ammonium compounds ('quats') and alcohol-based disinfectants showed no significant association with asthma control in a cohort of 4,102 US nurses (quats: OR 1.10, n=1,548 exposed, P-trend=0.14; alcohol: OR 1.11, n=1,591 exposed, P-trend=0.12), and the null for quats held in two further models adjusting for exposure to the other six disinfectant products.

Moderate evidence.

Source: Dumas 2017, European Respiratory Journal Link to this fact

Health effects / Review of other studies

A review of controlled chamber studies (carbon dioxide, ammonia, formaldehyde, sulfur dioxide, glycol/glycol-ether mixtures) found no consistent evidence that people with allergic rhinitis or mild asthma are more sensitive to sensory-irritant chemicals than non-allergic people.

Moderate evidence.

Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Review of other studies

The same authors' own worked example for ammonia — comparing a mouse near-zero-effect threshold (42 ppm) to the human no-effect level, then adding a further factor to account for ordinary variation between people — lands on a combined safety margin of about 4 to 5, not the smaller factor of about 2 that a later 2024 review attributes to this paper for protecting sensitive groups.

Moderate evidence.

Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Self-reported survey

The study found no association between childhood or adult hair product or hair oil use and mammographic breast density, a separate, strong breast-cancer risk factor, suggesting that if hair-product chemicals affect breast cancer risk, it may be through pubertal timing rather than breast density.

Moderate evidence: Small sample (N=248) limits power to detect a true but modest effect on breast density; one adult product subgroup (hair dye) did show a small positive association with density.

Source: McDonald 2018, Environmental Health Link to this fact

Health effects / Animal study

In rats exposed by nose-only inhalation to concentrated benzalkonium chloride (BKC) aerosols (37.6-52.8 mg/m3 for 4-6 hours over 3 days), animals developed increased relative lung weight and elevated total protein, LDH, and IgE in bronchoalveolar lavage fluid, indicating severe lung damage; the highest dose killed 2 of 5 animals.

Moderate evidence.

Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact

Health effects / Animal study

In mice, 30-minute inhalation exposure to benzalkonium chloride aerosol up to 19 mg/m3 produced a concentration-dependent decrease in tidal volume, an increase in respiratory rate, and neutrophilic lung inflammation; even the lowest tested dose (0.049 mg/m3) significantly decreased tidal volume.

Moderate evidence.

Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact

Health effects / Other evidence

Nebulized benzalkonium chloride has caused bronchoconstriction in sensitive severe asthmatics after prolonged (15-30 minute), repeated exposure to cumulative doses of about 300 micrograms; the affected multi-dose nebulizer formulations have since been replaced with BKC-free unit-dose vials.

Moderate evidence.

Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact

Health effects / Measured in people or real products

In a population-representative sample of about 2,900 Canadians (Canadian Health Measures Survey, 2012-2013), a 100% increase in measured residential indoor-air limonene was associated with a 17-18% relative increase in the adjusted odds of both wheezing (OR 1.17, 95% CI 1.16-1.18) and doctor-diagnosed asthma (OR 1.18, 95% CI 1.17-1.19), plus a 1.55% (95% CI 1.28-1.89) increase in exhaled nitric oxide (FeNO), an objective marker of airway inflammation.

Moderate evidence.

Source: Dales & Cakmak 2019, Environmental Pollution Industry-funded Link to this fact

Health effects / Lab study (cells or chemistry)

In a laboratory study, benzalkonium chloride (BAK), the most common eye-drop preservative, killed 50% of human corneal epithelial cells within about 1 to 5 minutes of exposure at concentrations (10-30 ug/mL) that fall within BAK's own reported clinical eye-drop concentration range (10-200 ug/mL).

Moderate evidence.

Source: Kabashima 2020, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact

Health effects / Lab study (cells or chemistry)

BAK exposure disrupted and reduced the tight-junction protein occludin and delayed recovery of transepithelial electrical resistance (a barrier-function measure) in a dose-dependent manner in human corneal epithelial cells, while a preservative-free trometamol/boric-acid/EDTA mixture (TBE) did not.

Moderate evidence: Single-lab, in vitro monolayer model; occludin densitometry and TEER recovery magnitude are partly chart-read (approx., read from Fig. 3 and Fig. 4F); no independent replication.

Source: Kabashima 2020, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact

Health effects / Measured in people or real products

Scaled to a realistic 90-square-meter apartment burning 5 candles for 3.5 hours, the highest-soot candle type produced an estimated fine-particle (PM2.5) concentration of 70 micrograms per cubic meter, above the WHO 24-hour air quality guideline of 25 micrograms per cubic meter, while the estimated cancer-risk marker (benzo[a]pyrene equivalent) stayed at, not above, the WHO guideline in both the highest- and lowest-emitting candle scenarios tested.

Moderate evidence.

Source: Andersen 2021, Indoor Air Link to this fact

Health effects / Measured in people or real products

When candle emissions were converted to realistic household exposure (a 30 m3 room, candle burning 4 hours a day, 4 days a week), most measured pollutants (carbon monoxide, carbon dioxide, formaldehyde, PM2.5, benzene, most VOCs) stayed below international indoor air guide values, but nitrogen dioxide, acrolein, and benzo[a]pyrene exceeded some (not all) of the guide values tested, depending on which health agency's reference value was used.

Moderate evidence.

Source: Salthammer 2021, Environment International Industry-funded Link to this fact

Health effects / Review of other studies

People with chemical intolerance or multiple chemical sensitivity react more strongly than healthy controls in controlled chamber exposures to irritant chemicals, with derived sensitivity factors typically 1 to 3 times higher and, in some studies, up to about 20 times higher.

Moderate evidence.

Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact

Health effects / Review of other studies

Benzalkonium chloride (BAK), the preservative used in about 70% of eye-drop formulations, is toxic to eye-surface cells at the concentrations it's commonly used (0.02-0.04%), which is 4 to 8 times its own cited cytotoxicity threshold of about 0.005%.

Moderate evidence.

Source: Goldstein 2022, Eye Industry-funded Link to this fact

Health effects / Review of other studies

Glaucoma patients on chronic BAK-preserved eye drops have ocular surface disease at much higher rates (30-70% across cited studies) than similarly aged adults without glaucoma (5-30%), and even a single 7-to-14-day course of BAK-preserved drops caused goblet-cell loss and other surface damage in eyes that started out healthy.

Moderate evidence.

Source: Goldstein 2022, Eye Industry-funded Link to this fact

Health effects / Lab study (cells or chemistry)

BAK's ocular toxicity is proposed to work partly through mitochondria: because BAK is positively charged and mitochondria are the only negatively charged compartment inside cells, cell studies cited in this review found BAK triggers oxidative stress and can inhibit mitochondrial function by more than 90%.

Moderate evidence: Mechanism drawn from in vitro/cell-culture studies cited by the review, not measured directly in intact human eyes.

Source: Goldstein 2022, Eye Industry-funded Link to this fact

Health effects / Review of other studies

Benzalkonium chloride (BAC), used at 0.005%-0.02% as an eye-drop preservative, is used at roughly 5-100 times that concentration (0.1%-1.0%) to deliberately induce dry-eye-disease signs in rabbit, mouse, and rat models.

Moderate evidence.

Source: Thacker 2023, Indian Journal of Ophthalmology Link to this fact

Health effects / Animal study

Topical BAC induces dry-eye-disease signs in animals through a detergent-like mechanism: it disrupts the tear film's lipid layer and causes corneal/conjunctival epithelial cell apoptosis, mitochondrial dysfunction, and DNA single-strand breaks, with elevated pro-inflammatory cytokines (IL-6, IL-8, IL-1β, TNF-α) and reduced mucin/goblet cells.

Moderate evidence.

Source: Thacker 2023, Indian Journal of Ophthalmology Link to this fact

Health effects / Animal study

In a rabbit dose-comparison study, 0.2% BAC (twice daily for 2 weeks) sustained dry-eye-disease signs for 3 weeks after BAC was stopped, versus only 1-2 weeks for 0.1% and 0.15% BAC.

Moderate evidence: Single-lab original data from this paper's own unpublished experiment, not yet independently replicated at these exact concentrations.

Source: Thacker 2023, Indian Journal of Ophthalmology Link to this fact

Health effects / Animal study

In the same rabbit study, both the fluorescein staining score and the corneal smoothness index rose with BAC concentration after 2 weeks: about 3 at 0.1%, about 4 at 0.15%, and about 5 at 0.2% (both scored on a 0-5 scale).

Moderate evidence: Approx., read from Fig. 3b/3c bar charts; the paper does not print these exact scores in the text.

Source: Thacker 2023, Indian Journal of Ophthalmology Link to this fact

Health effects / Lab study (cells or chemistry)

In cultured human corneal stromal fibroblasts, benzalkonium chloride (BAC) reduced cell viability and impaired mitochondrial respiration at concentrations 10-100,000 times lower than the classic ocular-surface-toxicity threshold (as low as 10^-8%-10^-6% vs. ~5×10^-3%).

Moderate evidence.

Source: Umetsu et al. 2024, Graefe's Archive for Clinical and Experimental Ophthalmology Link to this fact

Health effects / Lab study (cells or chemistry)

BAC dose-dependently suppressed mRNA expression of collagen I, collagen VI, and fibronectin in human corneal stromal fibroblasts, with collagen I significantly reduced even at the lowest concentration tested (10^-8%).

Moderate evidence: In vitro, 2D monolayer model, 2 donors; extracellular-matrix gene suppression has not been linked to a measured clinical outcome (e.g., corneal thinning) in this study.

Source: Umetsu et al. 2024, Graefe's Archive for Clinical and Experimental Ophthalmology Link to this fact

Health effects / Lab study (cells or chemistry)

BAC suppressed rather than activated the ER-stress/unfolded-protein-response pathway (GRP94, IRE1, PERK, ATF4, sXBP1, CHOP) in human corneal stromal fibroblasts, in a concentration-dependent manner, which the authors interpret as failure of an adaptive stress response rather than reassurance.

Moderate evidence: Interpretation (failed adaptive response) is the authors' own; ER-stress-gene suppression alone does not establish a clinical mechanism of corneal damage.

Source: Umetsu et al. 2024, Graefe's Archive for Clinical and Experimental Ophthalmology Link to this fact

Health effects / Measured in people or real products

No toxicological testing has been done on the specific nanoparticles formed during scented wax melt use; the authors explicitly call for future studies on their toxicological properties before drawing health conclusions.

Moderate evidence: This is the paper's own stated evidence gap, not a finding of harm or safety.

Source: Patra et al. 2025, Environmental Science & Technology Letters Link to this fact

Health effects / Lab study (cells or chemistry)

Exposing primary human bronchial epithelial cells (air-liquid interface culture) to a disinfectant-concentration (0.4%) benzalkonium chloride aerosol for 24 h produced 2,810 differentially expressed genes (1,475 up, 1,335 down), mapping onto DisGeNET disease networks for asthma, COPD, and pulmonary fibrosis; IL1RL1 and IL6R (upregulated) are independently reported as elevated in human asthma patients.

Moderate evidence.

Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact

Health effects / Lab study (cells or chemistry)

The two genes with the largest fold-change increases in BKC-exposed bronchial cells were both pulmonary-fibrosis-associated: FGF2 (11.4-fold) and GREM1 (19.4-fold).

Moderate evidence: No documented human case of BKC-caused pulmonary fibrosis exists; this is a gene-expression signal in one in vitro model, not a demonstrated disease outcome.

Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact

Health effects / Review of other studies

A narrative research review of 96 studies (32 human, 26 in vivo, 38 in vitro) on BKC respiratory toxicity found mixed clinical-trial results (some report impaired nasal ciliary motility and bronchoconstriction, others find no significant effect), a handful of occupational-asthma case reports, and animal-inhalation evidence of decreased tidal volume, inflammation, and histological changes resembling pulmonary fibrosis/obstructive lung disease; the authors conclude evidence that BKC causes respiratory disease in humans 'remains limited.'

Moderate evidence.

Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact

Health effects / Review of other studies

Hydrolyzed wheat protein used in cosmetics (facial creams, moisturizers, shampoos, gels) has caused immediate allergic reactions, including hives and anaphylaxis, in sensitized users when applied to the skin.

Moderate evidence.

Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact

Health effects / Review of other studies

Underarm body odor is mostly made by skin bacteria, not by sweat itself: apocrine-gland secretions are odorless when released, and only turn into the characteristic musk/urine smell after aerobic Corynebacteria metabolize odorless steroid precursors into 16-androstenes, or after bacteria break the goat-like acid 3-methyl-2-hexenoic acid free from its carrier proteins.

Moderate evidence: Review synthesis of older primary biochemistry literature, not this paper's own new data.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Health effects / Review of other studies

A single gene variant (ABCC11 538G->A) largely explains why most East Asians have a faint, acidic body odor instead of the strong axillary odor typical of Caucasians and Africans, and the same variant also determines dry vs. wet earwax.

Moderate evidence: Review synthesis of a single genetics study, not replicated here.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Health effects / Review of other studies

Several metabolic and infectious diseases have documented, specific body-odor signatures: trimethylaminuria smells of rotten fish in urine/sweat/breath/saliva/semen, diabetic ketoacidosis smells of acetone, maple syrup urine disease smells of caramelized sugar, and typhoid fever produces a musty or fresh-baked-bread body odor.

Moderate evidence: Compiled from decades-old, mostly single case-series/case-report literature, not systematically re-verified by this review.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Health effects / Review of other studies

Body odor changes measurably with age, but studies disagree on which compound tracks it: one GC study found dimethyl sulfone, benzothiazole, and nonanal correlating with age (and did not detect 2-nonenal), while a separate Japanese study found 2-nonenal rising sharply after age 39, the compound blamed for the so-called old man smell.

Moderate evidence: The review attributes the discrepancy to likely diet/cohort differences (the Japanese cohort's diet was unreported), not a resolved mechanism.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Health effects / Review of other studies

Diet measurably changes how pleasant other people rate a person's body odor: in a controlled study cited here, eating red meat decreased how pleasant axillary odor was rated.

Moderate evidence: Single cited study; effect size and diet duration not given in this review.

Source: Kippenberger 2012, Experimental Dermatology Link to this fact

Health effects / Lab study (cells or chemistry)

Among 62 individually tested deodorant ingredients, only fragrance chemicals (plus one insect-pheromone contaminant) showed any estrogenic activity; no carrier, stabilizer, emulsifier, plasticizer, antitranspirant, or other active ingredient (including triclosan and BHT) tested positive.

Moderate evidence: Only 62 of the many ingredients found by GC/MS screening were selected for individual testing, based on frequency of occurrence; ingredients not selected were not tested at all.

Source: Lange et al. 2014, Chemosphere Link to this fact

Health effects / Measured in people or real products

Acetaldehyde, a probable human carcinogen, rose far more than its boiling point alone would predict once candles were lit — one strawberry candle's on/off concentration ratio for acetaldehyde was 3,688-fold, the largest ratio of any of the 34 compounds tracked in the study.

Moderate evidence.

Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact

Health effects / Measured in people or real products

Kim et al. 2016 found their own original 2015 emission factors for carbonyl compounds from scented candles (formaldehyde and related aldehydes) had been computationally underestimated by exactly a factor of 250, due to a missed sample-dilution correction; the revised formaldehyde emission factor for the highest-emitting candle (SB-on) rose from 383 ng/g to 95.7 ug/g.

Moderate evidence: Single lab, self-corrected; independent replication of the corrected emission factors has not been reported.

Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact

Health effects / Measured in people or real products

A Korean government risk assessment of 64 deodorants found that at the maximum concentrations actually measured in the products, none of the 19 fragrance and biocidal ingredients carried to detailed (tiered 2) assessment exceeded its margin-of-exposure or hazard-quotient safety threshold, for either the inhalation or the dermal route.

Moderate evidence.

Source: Kim et al. 2018, Science of The Total Environment Link to this fact

Health effects / Review of other studies

Fragrance chemicals have been reported to cause immediate-type contact urticaria, photosensitivity reactions, and rarer miscellaneous effects such as depigmentation and orofacial granulomatosis, but the review characterizes all of these as currently rare and not causing significant clinical problems.

Moderate evidence: Causal relationship for the miscellaneous effects in Table 13 is explicitly stated by the review as "not always established beyond doubt" (mostly case reports).

Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact

Health effects / Animal study

Scented candle fumes alone, at an occupational-intensity chamber dose, significantly increased inflammatory cytokines (TNF-alpha, IL-6, IL-1beta) and NF-kB activity in the lungs of mice, and caused measurable lung histological injury, without significantly raising heart inflammatory markers, heart NF-kB, cardiac injury markers (LDH, CPK, CKMB), plasma BNP, or heart HIF-1alpha above unexposed controls.

Moderate evidence.

Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact

Health effects / Animal study

In mice, chronic social-disruption stress combined with scented candle fume exposure produced significantly worse cardiopulmonary inflammation and injury (BALF/lung/heart cytokines, NF-kB activity, serum LDH/CPK/CKMB, plasma BNP, heart HIF-1alpha, and lung histological injury) than either stress or candle fumes alone, though no group showed significant heart tissue histopathology.

Moderate evidence.

Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact

Health effects / Advocacy group testing

Six substances found in the tested perfumes are classed by this report as suspected endocrine disruptors: benzyl salicylate, BHT, butylphenyl methylpropional, ethylhexyl methoxycinnamate, ethylhexyl salicylate, and octocrylene.

Moderate evidence: 'suspected' means the substance appears on one or more screening/priority lists, not that endocrine disruption in humans at perfume-use doses has been demonstrated.

Source: Tegengif 2022 Link to this fact

Health effects / Advocacy group testing

Butylphenyl methylpropional, found in several of the tested perfumes, is the one substance in this report's list of 26 that is also classed as reprotoxic.

Moderate evidence.

Source: Tegengif 2022 Link to this fact

Health effects / Self-reported survey

Among 472 Saudi university students who used scented candles, 24.8% reported at least one adverse health symptom in the past 12 months, most commonly headache (15.2%), shortness of breath (8.9%) and cough (7.8%); skin irritation was rare (1.3%).

Moderate evidence.

Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact

Health effects / Self-reported survey

Among the same scented-candle users, respiratory-specific complaints in the past 12 months included waking with chest tightness (36.0%), waking from a coughing attack (33.1%), nasal allergy/hay fever (25.0%), a diagnosed respiratory illness (16.3%), a shortness-of-breath attack on waking (17.2%), wheezing (14.6%) and an asthma attack (9.5%).

Moderate evidence: Self-reported, non-clinically-confirmed symptoms in a non-representative convenience sample; no comparison group of non-candle-users was asked the same respiratory questions.

Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact

Health effects / Lab study (cells or chemistry)

An academic in vitro toxicology screen of Lilial (butylphenyl methylpropional, the fragrance chemical banned from EU cosmetics in 2022) found no cytotoxicity, no mutagenicity in a mammalian gene mutation assay, no nephrotoxicity, and no NF-κB or NRF2 stress-pathway activation, in either Lilial itself or its major liver-generated (S9) metabolites, up to 100 µM.

Moderate evidence.

Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact

Health effects / Lab study (cells or chemistry)

Using OECD/EPA guideline-validated receptor-transactivation assays (HeLa9903 for estrogen receptor, MDA-kb2 for androgen receptor), Lilial and its major liver metabolites showed no estrogen- or androgen-receptor agonist activity from 1 nM to 100 µM; the study's authors said they were unable to confirm the European Chemicals Agency's earlier suspicion that Lilial is an endocrine disruptor.

Moderate evidence: Single academic lab; this directly conflicts with a weaker, non-guideline finding from a different assay type (MCF7 proliferation) for the same compound — see contradiction.

Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact

Health effects / Lab study (cells or chemistry)

The mutagenic/genotoxic evidence for Lilial is genuinely mixed: bacterial Ames tests were mostly negative (one strain's positive result did not reproduce in a confirmatory test), a mammalian CHO/HPRT gene-mutation assay found no mutagenicity up to 500 µM with metabolic activation, but a DNA-strand-break (γH2AX) assay in the same paper gave results the authors themselves call inconclusive rather than negative.

Moderate evidence: The γH2AX result depended on which of two readouts (fold-change vs. area-normalized fluorescence) was used, and these disagreed in most of the conditions tested.

Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact

Health effects / Other evidence

Polycyclic aromatic hydrocarbons identified as carcinogens, including naphthalene, anthracene, and pyrene, have been found in candle fumes from wax, aroma substances or combustion dyes.

Moderate evidence: Directionally consistent with our own chamber PAH data (Salthammer 2021, Andersen 2021), though the editorial's own citation (Orecchio 2011) is not itself in this evidence base.

Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact

Health effects / Animal study

In rats, burning a scented candle 1-6 hours/day for 8 weeks in a sealed room raised serum TNF-alpha to about 115-220 pg/mL and IL-6 to about 120-215 pg/mL (both approximate, read from Fig. 3), versus about 30 and 50 pg/mL in fresh-air controls, and caused progressively worse lung damage on histopathology, reaching severe injury (fibrosis, necrobiotic changes, dense inflammatory infiltration) after as little as 3 hours/day.

Moderate evidence.

Source: Mohamed et al. 2025, Frontiers in Public Health Link to this fact

Health effects / Government agency

An international expert working group convened by the World Health Organization and UN Environment Program concluded that close to 800 chemicals are known or suspected to interfere with hormone receptors, hormone synthesis, or hormone conversion, but only a small fraction of them have been tested for whether they actually cause overt endocrine effects in an intact organism.

Moderate evidence.

Source: WHO/UNEP 2012 Link to this fact

Health effects / Government agency

Animal studies show that mixtures of endocrine-disrupting chemicals can produce additive effects even when every chemical in the mixture is present at a level too low, on its own, to cause any observable effect, meaning many 'individually safe' exposures could add up to a harmful one.

Moderate evidence.

Source: WHO/UNEP 2012 Link to this fact

Health effects / Government agency

Hormone-disrupting chemicals often do not follow a simple 'more dose equals more effect' pattern; some show non-monotonic dose-response curves, so standard toxicology testing at high doses, divided by a safety factor to estimate a low 'safe' dose, may miss real effects that occur only at low doses.

Moderate evidence: This is the report's own methodological critique of standard regulatory toxicology testing, not a finding about any specific chemical.

Source: WHO/UNEP 2012 Link to this fact

Health effects / Other evidence

A widely cited 2012 review (Vandenberg et al.) cataloged many examples of endocrine-disrupting chemicals producing non-monotonic (U-shaped) dose-response curves; an independent 2013 Danish government reanalysis of that same catalog found that 45% of its cited in vitro examples were artifacts of general cell toxicity rather than true hormone-mediated effects, and only 5 of 34 cited in vivo (whole-animal) examples showed clear evidence of a genuine non-monotonic response.

Moderate evidence.

Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Other evidence

The WHO-UNEP 2012 report changed its conclusion on PCBs and DDT causing adrenocortical hyperplasia (Cushing-like adrenal gland disease) in Baltic seals from 'uncertain association' in the WHO's 2002 report to 'sufficient evidence' of a causal link in 2012, without citing any new supporting data, while not addressing contrary findings that tie similar adrenal changes in other marine mammals to chronic stress rather than chemical exposure, and rat studies finding the opposite direction of adrenal effect (atrophy, not hyperplasia) from the same chemicals.

Moderate evidence: From an industry-funded critique paper; the underlying wildlife and rat studies have not yet been read as primaries by this evidence base.

Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Other evidence

The WHO-UNEP 2012 report's claim that the rise in autism spectrum disorder (ASD) prevalence is at least partly caused by environmental factors, including endocrine-disrupting chemicals, rests on only two citations (from 1976 and 2007); separate, non-industry-affiliated research attributes much of the reported increase in ASD prevalence to changes in diagnostic criteria, broader case ascertainment, and diagnostic substitution (children previously diagnosed with intellectual disability now diagnosed with ASD) rather than to any confirmed environmental cause.

Moderate evidence.

Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Other evidence

In a mouse study the WHO-UNEP 2012 report cites as evidence that DES and the plant estrogen genistein cause endometrial cancer, the doses of DES used were more than 1,000 times a typical daily estrogen dose from a low-dose oral contraceptive, and the genistein dose was more than 50 times the highest human daily dietary intake reported in a high-soy-consuming population; the study also used mice bred with a genetic defect in DNA-repair, a detail the WHO-UNEP report does not mention.

Moderate evidence: Single cited animal study; dose-comparison figures come from the critique paper's own calculations, not independently re-verified here.

Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Health effects / Government agency

The European Commission states that 'a share of scientists' holds that no safe threshold can be established for endocrine disruptors at all, an open scientific question the Commission says still needs to be resolved.

Moderate evidence.

Source: EU Commission 2018 Link to this fact

Health effects / Animal study

Repeated animal studies attribute transgenerational reproductive effects of endocrine-disrupting chemicals to epigenetic changes (DNA methylation, histone modification, noncoding RNA) transmitted through the germline to descendants who were never themselves exposed to the chemical, rather than to a new genetic mutation.

Moderate evidence.

Source: Brehm & Flaws 2019, Endocrinology Link to this fact

Health effects / Review of other studies

Antiperspirants do not stop sweating; astringent aluminum or aluminum-zirconium salts narrow the sweat duct and reduce underarm sweat emission by only about 50%.

Moderate evidence: Secondhand via a narrative review; the underlying efficacy studies are not individually cited by concentration here.

Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact

Health effects / Other evidence

Aluminum from antiperspirants penetrates intact skin only in tiny amounts (up to 0.07% of the applied dose in an in vitro Franz-cell study), but rose roughly 6-fold on damaged or shaved skin, reaching 11.5 micrograms per square centimeter.

Moderate evidence: Single in vitro study on excised human skin, known only secondhand via this review; primary (Pineau 2012) not yet in our evidence base.

Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact

Health effects / Review of other studies

Multiple independent expert reviews (a 2008 oncology/pharmacology literature review, France's Afssaps in 2011, and the EU's Scientific Committee for Cosmetic Products in 2014) found no conclusive evidence that antiperspirant aluminum causes breast cancer or Alzheimer's disease.

Moderate evidence.

Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact

Health effects / Test-chamber measurement

Scented candle fumes failed to reduce chronic-stress-induced serum corticosterone and instead increased inflammatory biomarkers, proinflammatory cytokine production, and NF-kB activation in the lungs and heart, causing cardiopulmonary injury.

Moderate evidence.

Source: Singh 2023, Environmental Science & Technology Link to this fact

Health effects / Review of other studies

In a systematic review of 15 human studies, 11 found significantly higher bisphenol A (BPA) in the blood, urine, or follicular fluid of women with polycystic ovary syndrome (PCOS) than in women without it, with several also finding positive correlations between BPA and testosterone, androstenedione, insulin resistance, or low-grade inflammation markers.

Moderate evidence.

Source: Srnovršnik 2023, Life Link to this fact

Health effects / Lab study (cells or chemistry)

In a lab-grown 3D model of human skin, fragmented polystyrene particles smaller than about 2 micrometers reached the epidermis within about an hour of a single dose and the dermis within about two hours, peaking at an average of 4.7 micrograms in the dermis after 6 hours, and dose-dependently switched on inflammation genes and proteins (IL-1alpha, IL-1beta, IL-18, IL-6, IL-8, ICAM-1, FOS, JUN) at both the mRNA and protein level.

Moderate evidence.

Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact

Health effects / Animal study

In live hairless mice given fragmented polystyrene topically on shaved skin once a day for two weeks, only about 0.04% to 0.12% of the total applied plastic was detectable in the skin afterward, yet the treated skin still showed a significant, dose-dependent increase in the same inflammatory genes and proteins seen in the lab skin model, with no change in body or liver weight.

Moderate evidence.

Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact

Health effects / Lab study (cells or chemistry)

In donated human abdominal skin dosed daily with fragmented polystyrene for 10 days, the plastic reached depths of about 183 to 291 micrometers (into the dermis) and penetrated proportionally more than in mouse skin given a similar daily dose — roughly 1.7% of the applied dose in human skin versus about 0.04% in mouse skin at the lower dose level — which the authors attribute to human hair follicles being much larger than mouse hair follicles.

Moderate evidence.

Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact

Health effects / Lab study (cells or chemistry)

Fragmented polystyrene was cytotoxic to human skin keratinocytes and dermal fibroblasts in culture at concentrations above 200 micrograms per milliliter over 24 hours, with visible cell membrane and cytoskeleton damage at 400 micrograms per milliliter; below that, the plastic was still taken up into the cytosol of both cell types at 100 micrograms per milliliter without killing them.

Moderate evidence: Cell-culture (2D monolayer) result, not skin tissue; concentrations are not benchmarked against any measured real-world skin exposure.

Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact

Health effects / Lab study (cells or chemistry)

RNA sequencing of human keratinocytes exposed to fragmented polystyrene found nearly 4,700 genes with altered activity, with pathway analysis pointing to the p53, IL-17, and TNF inflammatory signaling pathways as significantly affected.

Moderate evidence.

Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact

Health effects / Review of other studies

Across multiple large studies and meta-analyses, people with higher levels of the plastic chemical bisphenol A (BPA) in their urine or blood have consistently higher rates of obesity and abdominal obesity; one meta-analysis found an 11% increase in obesity risk for every 1 ng/mL rise in blood BPA.

Moderate evidence.

Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact

Health effects / Review of other studies

In mouse, rat, and zebrafish studies, bisphenol A and phthalates such as DEHP promote weight gain by switching on the master fat-cell gene PPAR-gamma, boosting appetite-driving brain chemicals (neuropeptide Y and AgRP), and triggering low-grade inflammation in fat tissue, often at doses meant to mimic real-world human exposure.

Moderate evidence.

Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact

Health effects / Review of other studies

A 2025 systematic review of 18 human studies found bisphenol A, phthalates, and the UV filter octocrylene positively associated with polycystic ovary syndrome (PCOS) in most (though not all) of the studies that tested them.

Moderate evidence.

Source: Ozga & Jurewicz 2025 Link to this fact

Health effects / Measured in people or real products

A 2025 global disease-burden model estimates that DEHP exposure from plastics was linked to about 356,000 cardiovascular deaths worldwide in 2018 (about 13.5% of CV deaths among 55-64-year-olds), and about 10.5 million years of life lost.

Moderate evidence.

Source: Hyman 2025, eBioMedicine Link to this fact

Health effects / Measured in people or real products

The estimated DEHP-attributable cardiovascular mortality burden falls hardest on the Middle East, South Asia, East Asia, and the Pacific, which together account for about 73% of all estimated DEHP-attributable deaths, while the USA and Europe show the lowest attributable share (about 10% and 8%).

Moderate evidence.

Source: Hyman 2025, eBioMedicine Link to this fact

Health effects / Measured in people or real products

Countries with large aging populations and expanding plastics industries — India, China, and Indonesia — bear the largest absolute numbers of DEHP-attributable cardiovascular deaths in 2018 (about 104,000, 61,000 and 20,000 respectively).

Moderate evidence: Modeled estimate built on country-level population and mortality-rate data, not a direct count of deaths caused by DEHP.

Source: Hyman 2025, eBioMedicine Link to this fact

Health effects / Other evidence

In a 2004 FDA laboratory study, two of three chemicals that penetrated into skin and stayed there after 24 hours (a self-tanning ingredient and a hair-dye ingredient) were shown, using an extended 72-hour test, not to actually enter the bloodstream in any meaningful additional amount.

Moderate evidence: Single FDA lab, in vitro diffusion-cell system (not in vivo humans); findings are chemical-specific, not a general rule about skin-retained chemicals.

Source: Yourick 2004, Toxicology and Applied Pharmacology Link to this fact

Health effects / Lab study (cells or chemistry)

In FDA's own lab tests, only about 0.1% of the diethanolamine (DEA) applied in real shampoo and hair-dye products reached the receptor fluid (the in vitro proxy for systemic absorption) after a normal 5-30 minute use; 96-98% of the DEA that penetrated the skin stayed lodged there instead.

Moderate evidence: Single-lab, in vitro, excised human skin diffusion-cell model; not a human in vivo measurement; n=2 products per class.

Source: Kraeling 2004, Food and Chemical Toxicology Link to this fact

Health effects / Lab study (cells or chemistry)

With body lotion left on skin for 24 hours, up to about 15% of applied DEA penetrated the skin, and 3 consecutive days of lotion use built DEA up in skin to nearly 30% of the applied dose, but systemic absorption into the receptor fluid still stayed under 1% each day.

Moderate evidence.

Source: Kraeling 2004, Food and Chemical Toxicology Link to this fact

Health effects / Government agency

Air fresheners accounted for only 0.58% of all 2.4 million chemical exposures reported to US poison control centers in 2005, and 95% of the resulting injuries were minor; deodorizers (the category containing air fresheners) ranked 20th of 23 product categories for pediatric poison-control exposures.

Moderate evidence.

Source: EPA 2007, citing AAPCC 2005 Link to this fact

Health effects / Other evidence

In a 2011 in vitro study on human cadaver abdominal skin, undiluted propylene glycol crossed the skin at a measured steady-state rate of about 97.6 micrograms per square centimeter per hour, and dipropylene glycol crossed about 2.5 times more slowly, at about 39.3 micrograms per square centimeter per hour.

Moderate evidence.

Source: Fasano 2011, Toxicology in Vitro Industry-funded Link to this fact

Health effects / Government agency

IARC classifies benzophenone (CAS 119-61-9) as Group 2B, possibly carcinogenic to humans, based on sufficient evidence in experimental animals: dose-related liver tumors (hepatocellular adenoma, and rare hepatoblastoma) in male mice, histiocytic sarcoma in female mice, renal tubule adenoma in male rats, and mononuclear-cell leukemia in rats, from two 2-year NTP feed studies; no human cancer data exist on benzophenone.

Moderate evidence.

Source: IARC 2013 Link to this fact

Health effects / Government agency

Benzophenone's oxidative metabolite 4-hydroxybenzophenone, which is estrogenic in vitro (MCF-7 cells, ERalpha binding) and in vivo (rat uterotrophic assay), can also be formed by ultraviolet or sunlight irradiation of benzophenone itself, not only by enzymatic metabolism; the Working Group noted this matters because benzophenone has been used as a UV filter in cosmetics.

Moderate evidence.

Source: IARC 2013 Link to this fact

Health effects / Other evidence

Across 11-13 published studies from 1943-2015 (human volunteers, animals, and excised skin), mineral oil and petrolatum ingredients in cosmetics consistently stayed in the outermost skin layer (the stratum corneum), with at most a few percent reaching deeper skin layers and none detected in blood in any study.

Moderate evidence.

Source: Petry et al. 2017, Toxicology Letters Industry-funded Link to this fact

Health effects / Review of other studies

A 1950s-70s antiseptic called hexachlorophene showed how a chemical that binds tightly to the skin's outer dead layer can be both protective and dangerous: routine hexachlorophene baths cut newborn staph-infection admissions from about 6.5% to 0.6%, but when 18 French children were accidentally exposed to 6% hexachlorophene talc in 1972, four died and others developed permanent neurological damage from the same skin-binding property letting the chemical build up to toxic levels.

Moderate evidence.

Source: Li, Cary & Maibach 2018, Archives of Dermatological Research Industry-funded Link to this fact

Health effects / Review of other studies

How long a chemical lingers in the outer layer of skin after being applied depends mainly on three things: its chemical structure (ionic/charged chemicals bind skin proteins more strongly), how hydrated the skin is, and how well the chemical dissolves in the product's carrier liquid — and, in one specific dataset (a set of six chemical warfare agent simulants), skin binding rose in step with how fat-soluble (lipophilic) the chemical was.

Moderate evidence.

Source: Li, Cary & Maibach 2018, Archives of Dermatological Research Industry-funded Link to this fact

Health effects / Measured in people or real products

IARC found no convincing evidence that styrene exposure causes lung cancer or other solid tumors in humans; the strongest human cancer evidence for styrene concerns lymphohematopoietic malignancies, especially AML and T-cell lymphoma, in reinforced-plastics-industry cohorts.

Moderate evidence.

Source: IARC 2019 (Vol. 121) Link to this fact

Health effects / Animal study

Styrene-7,8-oxide, styrene's main metabolite, was separately classified by IARC in 2019 as Group 2A ("probably carcinogenic to humans") based on sufficient evidence in animals and strong mechanistic evidence that it is an electrophile which reacts directly with DNA and is genotoxic, even though human cancer evidence for styrene-7,8-oxide itself was rated "inadequate."

Moderate evidence.

Source: IARC 2019 (Vol. 121) Link to this fact

Health effects / Lab study (cells or chemistry)

Studies reviewed in the cosmetics industry's own 2021 benzophenone safety report found benzophenone-3 estrogenic in MCF-7 breast cancer cells (EC50 1.56-3.73 uM) and estrogenic/antiandrogenic in a yeast reporter assay (EC50 6.44 uM estrogen, 10.2 uM antiandrogen), and found benzophenone-1 and benzophenone-2 estrogen- and androgen-receptor-active in ovarian and prostate cancer cell lines; the industry panel's own Discussion and Conclusion do not address this data when reaching a 'safe' determination.

Moderate evidence.

Source: CIR 2021 Benzophenones Industry-funded Link to this fact

Health effects / Government agency

A study of 423 patients cited in the cosmetics industry's own 2021 benzophenone safety report found a positive association between women's urinary benzophenone-3 levels and the incidence of Hirschsprung's disease, with the cited authors noting that sunscreen use can expose a fetus to benzophenone-3 during the weeks 5-12 gestational window in which neural crest cell migration (implicated in the disease) occurs; the industry panel's Discussion and Conclusion do not address this study.

Moderate evidence: Single case-control study (China); association, not established causation; reported by CIR without further discussion or rebuttal in its Discussion/Conclusion sections.

Source: CIR 2021 Benzophenones Industry-funded Link to this fact

Health effects / Review of other studies

The Endocrine Society's April 2025 Position Statement defines an endocrine-disrupting chemical as "an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action," and states that because non-monotonic dose responses are common, it cannot be assumed there are non-zero thresholds below which EDC exposure is safe.

Moderate evidence.

Source: Endocrine Society 2025 Link to this fact

Health effects / Self-reported survey

More than half of Canadians with MCS surveyed (52%) said their current housing exposed them to mold or other symptom-triggering conditions, and 15% (18/119) fell into the paper's homeless category: moving frequently, living in a vehicle or tent, or staying with friends or family.

Moderate evidence.

Source: Diallo 2026 Link to this fact

Health effects / Other evidence

The Endocrine Society's definition of an endocrine-disrupting chemical covers interference with any aspect of hormone action, including hormone synthesis, not only interference at hormone receptors.

Moderate evidence.

Source: Sharma 2024, Biomolecules Link to this fact

Health effects / Review of other studies

Formaldehyde, released by household cleaning products both directly and via reaction with indoor ozone, is described as a human carcinogen as well as a respiratory irritant.

Moderate evidence.

Source: Rossignol 2013, Atmospheric Environment Link to this fact

Health effects / Government agency

The WHO/UNEP 'State of the Science of Endocrine Disrupting Chemicals — 2012' report's Concluding Remarks state verbatim that endocrine disruptors are 'a global threat that needs to be resolved.'

Moderate evidence.

Source: WHO/UNEP 2012 Link to this fact

Health effects / Measured in people or real products

BPA was detected in 93% of urine samples tested in the US NHANES national biomonitoring survey.

Moderate evidence.

Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact

Hidden ingredients / Measured in people or real products

In a test of 6 best-selling US air fresheners and laundry products, researchers found 98 chemical detections (58 different chemicals) released into the air; none appeared on any product label, and only 1 (ethanol) appeared on a safety data sheet.

Moderate evidence: N=6 products, headspace only, semi-quantitative.

Source: Steinemann 2009, Environmental Impact Assessment Review Link to this fact

Hidden ingredients / Measured in people or real products

4 of the 6 products released at least one chemical the Clean Air Act classifies as a hazardous air pollutant (acetaldehyde, chloromethane, or 1,4-dioxane), and none was listed.

Moderate evidence: Paper text says 5 of 6; tables support 4. Two of three HAPs come from the base formulation, not fragrance.

Source: Steinemann 2009, Environmental Impact Assessment Review Link to this fact

Hidden ingredients / Self-reported survey

68.6% of Australians were unaware that fragrance ingredients don't have to be fully listed on labels.

Moderate evidence: Awareness survey item.

Source: Steinemann 2017, Preventive Medicine Reports Link to this fact

Hidden ingredients / Self-reported survey

73.4% of Swedes didn't know fragrance ingredients don't have to be fully disclosed, and 70.9% didn't know that fragranced products sold as 'green' or 'organic' can also release potentially hazardous air pollutants.

Moderate evidence: Awareness items; the HAP premise itself rests on other studies.

Source: Steinemann 2018 (Sweden), Air Quality, Atmosphere & Health Link to this fact

Hidden ingredients / Measured in people or real products

When researchers tested 25 best-selling US laundry, cleaning, personal-care, and air-freshener products, they found 133 different chemicals released into the air, but only 1 of them was listed on any product label.

Moderate evidence: Single headspace sample per product; VOC counts depend on detection threshold.

Source: Steinemann 2011, Environmental Impact Assessment Review Link to this fact

Hidden ingredients / Measured in people or real products

11 of 25 best-selling fragranced products (44%) released at least one chemical the EPA classes as a probable cancer-causing air pollutant, such as acetaldehyde or 1,4-dioxane, though the study couldn't tell whether these came from the fragrance or the rest of the formula.

Moderate evidence: Headspace, not exposure; mostly base-formula compounds.

Source: Steinemann 2011, Environmental Impact Assessment Review Link to this fact

Hidden ingredients / Self-reported survey

About two-thirds (64.6%) of US adults did not know fragrance ingredients don't have to be listed on the label, and more than half would prefer fragrance-free workplaces (53.2% vs 19.7% against) and health care (54.8% vs 22.4%).

Moderate evidence: Opinion survey.

Source: Steinemann 2016, Air Quality, Atmosphere & Health Link to this fact

Hidden ingredients / Measured in people or real products

Counting the word "parfum" undercounts scented children's products, because essential oils and individual fragrance chemicals are listed under other names.

Moderate evidence: Undercount size not measured for these products.

Source: Uber 2024, Jornal de Pediatria (Rio de Janeiro) Link to this fact

Hidden ingredients / Measured in people or real products

In a test of 42 fragranced baby products (shampoos, lotions, oils, sprays), 95% of the chemicals they released into the air were not listed on the label, safety data sheet, or company website.

Moderate evidence: Headspace presence only; Australian products.

Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact

Hidden ingredients / Measured in people or real products

The best-selling US laundry detergent's label and safety sheet disclosed almost none of what it released; only ethanol was listed.

Moderate evidence: Same detergent measured in 2009, 2011, and 2013 papers; count once.

Source: Steinemann 2013, Air Quality, Atmosphere & Health Link to this fact

Hidden ingredients / Review of other studies

One product's safety data sheet listed twelve ingredients, every one of them only as 'trade secret' at '1-100%'.

Moderate evidence: Single example cited by EPA authors.

Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact

Hidden ingredients / Review of other studies

In a German test of six air fresheners, more than 90% of the chemicals they released were not declared on the product.

Moderate evidence: Secondary citation of Uhde & Schulz 2015 (not in our evidence base); by number of substances (>75% by concentration).

Source: Steinemann 2017, Building and Environment Link to this fact

Hidden ingredients / Review of other studies

Fragrance turns up in products people don't think of as scented: household cleaners and detergents, tampons and panty liners, medicines, medical devices, toys, and candles.

Moderate evidence: Qualitative list of exposure sources.

Source: Sukakul 2024, Acta Dermato-Venereologica Industry-funded Link to this fact

Hidden ingredients / Self-reported survey

When companies replace a chemical of concern, they often swap in one with far less safety data; one firm found a supplier's 'safer' substitute only looked safer because more of its ingredients were kept confidential.

Moderate evidence: Interview quotes and one anecdote.

Source: Scruggs 2011, Environmental Science & Policy Link to this fact

Hidden ingredients / Review of other studies

Testing cited by a 2010 review claimed the fragrance solvent DEP was found in all fragrances tested and in 71% of cosmetics, but the largest independent survey since (Koniecki 2011, n=252) found DEP in 70% of fragrances and 41% of cosmetics overall — lower than either earlier figure.

Moderate evidence.

Source: Crinnion 2010, Alternative Medicine Review Link to this fact

Hidden ingredients / Review of other studies

FDA's voluntary cosmetic registration listed benzyl alcohol in only 322 formulations in 1998 and 511 products in 2006, far below its real use in moisturizers, shampoos, baby products, and deodorants, which the authors call widespread under-reporting.

Moderate evidence.

Source: Jacob & Barron 2007, Dermatitis Link to this fact

Hidden ingredients / Review of other studies

The glycol-ether solvent propylene glycol methyl ether (PGME), mostly used in industrial coatings and cleaners, is officially listed as a possible 'fragrance ingredient' in cosmetics, and a Swiss survey found it making up 30–50% of one perfume.

Moderate evidence: INCI function listing plus one Swiss product survey (Dentan 2000, cited secondhand); US registry shows only nail-product uses.

Source: CIR 2008, International Journal of Toxicology Industry-funded Link to this fact

Hidden ingredients / Review of other studies

The single word 'fragrance' on a label can stand for dozens to hundreds of chemicals. The fragrance industry's own inventory (RIFM) lists about 2,600 chemicals in current active use, plus roughly 3,500 discontinued materials it keeps only for internal read-across comparison.

Moderate evidence.

Source: Rádis-Baptista 2023, Journal of Xenobiotics Link to this fact

Hidden ingredients / Review of other studies

Several hundred different label names can signal fragrance (chemical names, over 50 essential oils by common or Latin name, and synonyms such as aroma, parfum, perfume, and scent), so dermatologists say allergic patients are very unlikely to find fragrance-free products by reading labels alone.

Moderate evidence: Expert opinion.

Source: Rodriguez 2024, Cutis Link to this fact

Hidden ingredients / Review of other studies

A violet-water cologne that doctors reported as a lavender-oil exposure in a boy with breast growth declared no essential oil on its ingredient list, and an essential-oil industry group's lab analysis found none; it reported a synthetic fragrance allergen (alpha-isomethyl ionone), azo dyes, and diethyl phthalate instead. Go by the ingredient list of the actual product, not its scent name.

Moderate evidence.

Source: Braunstein & Braunstein 2023, touchREVIEWS in Endocrinology Industry-funded Link to this fact

Hidden ingredients / Review of other studies

Nobody independently analyzed the products used by the children in the 2019 lavender breast-growth case reports: the only published analysis was by an essential-oil trade consortium, which covered two of the three products and reported no numbers; the researchers concede the products contain other, partly synthetic, substances whose composition may vary by where they were bought.

Moderate evidence.

Source: Ramsey et al. 2020 (JCEM reply), The Journal of Clinical Endocrinology & Metabolism Link to this fact

Hidden ingredients / Self-reported survey

About a third of the personal care products people actually used were not in EWG's Skin Deep database at all, including 39% of perfumes and nearly all intimate-care products, so their hazards could not be rated.

Moderate evidence: Database coverage as of July 2022; EWG has since added products.

Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact

Hidden ingredients / Measured in people or real products

Once in the air, scent chemicals such as linalool, ionones, and the woody musk OTNE ('Iso E Super') reacted with ozone to form dozens of new oxidized chemicals, including a hydroperoxide. None of these was in the product.

Moderate evidence: Compound identities are tentative (formula-level mass spectrometry); products unquantified; no hazard testing.

Source: Wu 2024, Environmental Science & Technology Letters Link to this fact

Hidden ingredients / Animal study

The regulatory endocrine dossier on linalool tested 99.7%-pure, freshly handled material — not the air-oxidized linalool that forms in an opened bottle and that accounts for almost all of linalool's known allergy risk. Nobody has tested whether oxidized linalool is hormonally active.

Moderate evidence: This is standard and correct practice for a REACH dossier; it is a limit on what the result covers, not a flaw in the study.

Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact

Hidden ingredients / Review of other studies

Plastic particles are added to cosmetics on purpose for texture, a silky or powdery feel, opacity, shimmer, and as carriers for other ingredients, not only as scrub beads; and the EU chemicals agency's definition does not count liquid, semi-solid, or water-soluble polymers as microplastics.

Moderate evidence: Definition statement is the review's reading of ECHA; check against Regulation (EU) 2023/2055.

Source: Han & Kim 2025, Cosmetics Link to this fact

Hidden ingredients / Review of other studies

PFOA and GenX, both EU Substances of Very High Concern, may be used in making PTFE; a 2024 review says these impurities must be kept to a minimum but reports no measured levels in cosmetics, and the label says only 'PTFE'.

Moderate evidence.

Source: Jomaa 2024, Journal of the Netherlands Society of Toxicology (JNST) Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

In 2018, testing commissioned by Breast Cancer Prevention Partners of 25 personal care and 7 cleaning products found chemicals flagged for cancer, hormone disruption, respiratory, or developmental hazards that were not on the label; 99 of the 124 were on the fragrance industry's own ingredient list.

Moderate evidence: Not peer reviewed; labs, detection limits, and concentrations not reported; hazard = database flag; IFRA list includes multifunctional solvents/preservatives.

Source: BCPP 2018 Link to this fact

Hidden ingredients / Advocacy group testing

In a 2010 survey of more than 11,000 Canadian personal-care products with ingredient lists, 'fragrance' or 'parfum' was the most common ingredient of concern, listed on 56% of products and on about two-thirds of shampoos, soaps, and deodorants.

Moderate evidence: Self-selected volunteers read labels; product entries not de-duplicated; 2010 formulations; label count is a lower bound on fragranced products.

Source: David Suzuki Foundation 2010 Link to this fact

Hidden ingredients / Measured in people or real products

Lab tests commissioned by US campaigners found 38 chemicals not listed on the label across 17 popular perfumes; 10 of them had no published safety data at all.

Moderate evidence: NGO report, not peer reviewed; relayed through a student thesis; cite the report itself.

Source: Sarantis et al. 2010 (Not So Sexy), via Gilton 2011 Link to this fact

Hidden ingredients / Review of other studies

Sanitary pads, panty liners and tampons can contain undisclosed fragrance allergens — chiefly alpha-isomethyl ionone (in every scented tampon tested), hexyl cinnamal, and benzyl salicylate, plus trace limonene, linalool, and geraniol — and in the EU they do not have to declare any of them.

Moderate evidence.

Source: Pastor-Nieto 2021 (Desmedt 2020), Current Treatment Options in Allergy Link to this fact

Hidden ingredients / Lab study (cells or chemistry)

Eight of nine cosmetic UV filters tested were estrogenic in human breast-cancer cells, and six of nine increased uterine weight in immature rats; avobenzone (butyl methoxydibenzoylmethane) was the one inactive in every assay.

Moderate evidence.

Source: Schlumpf 2004, Toxicology Link to this fact

Hidden ingredients / Measured in people or real products

In one of the best-known reports linking 'lavender' products to breast growth in children, the boy's violet-water cologne declared no essential oil on its ingredient list; the essential-oil industry's own analysis found none, but reported a synthetic fragrance allergen (alpha-isomethyl ionone), azo dyes, and diethyl phthalate, a fragrance solvent suspected of hormone disruption.

Moderate evidence: Industry-funded letter; GC-MS/LC-MS/MS results given as prose with no concentrations, detection limits, lab or sample provenance; not independently confirmed.

Source: Giroux & Orjubin 2020 (JCEM letter; Consortium Huiles Essentielles), The Journal of Clinical Endocrinology & Metabolism Industry-funded Link to this fact

Hidden ingredients / Review of other studies

The only chemical analysis ever published of the products named in the 2019 lavender breast-growth case reports was done by an essential-oil trade group, covered two of the three products, and reported no numbers.

Moderate evidence: True of the published literature as read; the NIEHS reply to this letter (dgaa227) has not been read.

Source: Giroux & Orjubin 2020 (JCEM letter; Consortium Huiles Essentielles), The Journal of Clinical Endocrinology & Metabolism Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

In a Belgian test of 10 scented tampons, panty liners, and pads, 8 of the 24 fragrance allergens that EU cosmetics must name were found; all 4 tampons and 1 liner held at least one above 10 µg/g, the level at which a cosmetic would have to list it, and none named any allergen on the pack.

Moderate evidence: 10 products from one country (2019); presence in product, not transfer to the body; mostly weak sensitizers at 0.001-0.01%.

Source: Desmedt 2020, Contact Dermatitis Link to this fact

Hidden ingredients / Measured in people or real products

The fragrance allergens found most in scented tampons were α-isomethyl ionone (in every tampon, 12.6-19.1 µg/g) and hexyl cinnamal, not the familiar citrus and lavender terpenes.

Moderate evidence: N=4 tampons, Belgian market; limonene/linalool may be under-read by a headspace method that sees parents only.

Source: Desmedt 2020, Contact Dermatitis Link to this fact

Hidden ingredients / Review of other studies

FDA's own 1998 registry data, reproduced in full by the industry's cosmetic safety panel, show benzyl alcohol's biggest single cosmetic use was hair dye (130 of 1,572 formulations), with smaller counts in baby shampoo (5 of 21), baby lotion (3 of 53), moisturizers (8 of 769) and body/hand skin care (16 of 796).

Moderate evidence: Voluntary registry counts (Jan 1998); concentration-of-use reporting to FDA had already stopped by 1992 per the same report, so these are presence counts, not amounts used.

Source: Nair 2001 (CIR Expert Panel), International Journal of Toxicology Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

A 2024 lab study of six cosmetics found that ingredient labels can misdescribe the PFAS actually present: one product's named ingredient (a silane) appeared to be a different molecular isomer than the standard, and another's named phosphate-ester ingredient did not disclose that it contained shorter fluorocarbon chain lengths than its name implies.

Moderate evidence: Small sample (6 products from one country, 2 with naming issues); does not establish how common INCI-naming errors are across the wider market.

Source: Namazkar 2024, Environmental Science: Processes & Impacts Link to this fact

Hidden ingredients / Measured in people or real products

Benzyl alcohol, a fragrance allergen dubbed the "covert fragrance," was found in 32 of 533 US baby and children's personal care products (6%) with no "fragrance," "perfume," or "parfum" wording anywhere on the label.

Moderate evidence: Doesn't establish whether these products are marketed "fragrance-free"; measures label wording, not chemical content verification.

Source: Bonchak 2018, Dermatitis Link to this fact

Hidden ingredients / Measured in people or real products

Only 16% of the chemicals detected above the testing limit in these hair products were listed anywhere on the product label; fragrance ingredients were almost never named individually, appearing instead as the single word "fragrance".

Moderate evidence: Label concordance rose to 54% only for the highest-concentration chemicals (>1000 ug/g); 28 product/component labels checked.

Source: Helm 2018, Environmental Research Link to this fact

Hidden ingredients / Animal study

The air freshener's exact formulation is proprietary; GC/MS of its emissions identified toluene, limonene, alpha- and beta-pinene, terpinolene, sabinene, and about a dozen other volatiles the consumer has no way to learn about from the label.

Moderate evidence: Qualitative GC/MS of one product, one test atmosphere, recoveries unknown; only peaks with 90%+ library-match certainty reported; brand unnamed.

Source: Anderson & Anderson 1997, Archives of Environmental Health Link to this fact

Hidden ingredients / Measured in people or real products

FDA's own testing of 48 consumer cosmetic products found the fragrance solvent diethyl phthalate (DEP) in all 5 fragrance products tested, at levels up to 38,663 parts per million (3.9% by weight), and in 27 of 48 products overall, though phthalate esters were named on the ingredient list of only some nail products, never on fragrance.

Moderate evidence: Single FDA laboratory, 48 products bought in the Washington DC area (~2003-05), method-validated HPLC-UV; concentration in the product, not absorbed dose.

Source: Hubinger & Havery 2006, Journal of Cosmetic Science Link to this fact

Hidden ingredients / Measured in people or real products

A common personal-care-product ingredient can appear on ingredient labels under several different chemical names (the silicone D5 may be listed as 'cyclopentasiloxane' or 'cyclomethicone'), which may not read as the same substance to a consumer trying to identify or avoid it.

Moderate evidence: Based on this study's own tested product labels and general INCI naming conventions for volatile methyl siloxanes, not a systematic label-disclosure survey.

Source: Coggon 2018, Environmental Science & Technology Link to this fact

Hidden ingredients / Measured in people or real products

Independent laboratory testing not funded by the essential-oil or fragrance industry chemically confirmed that one of these colognes genuinely contained lavender oil (linalool and linalyl acetate), the only time this has been done for an actual implicated product in this literature rather than a reference oil bought for a lab study.

Moderate evidence.

Source: Diaz 2016, Journal of Pediatric Endocrinology and Metabolism Link to this fact

Hidden ingredients / Other evidence

California state scientists estimate that the mass of PFAS in cosmetics is concentrated not in makeup but in shaving creams and gels, hair care products, facial cleansers, sun care products, and lotions and moisturizers, which together make up more than 90% of the total estimated PFAS mass in California cosmetics sold each year, while all makeup categories combined make up less than 3%.

Moderate evidence.

Source: Balan 2024, Environmental Science & Technology Link to this fact

Hidden ingredients / Measured in people or real products

Fragrance materials not known to occur in any natural essential oil were found in products marketed as natural: a 'natural' body lotion contained 0.082% alpha-amylcinnamic aldehyde, a concentration that would require the essential oil itself to be about 16% pure synthetic aldehyde if it came from any known essential oil at typical use levels — evidence the 'natural' formulation included added synthetic fragrance material.

Moderate evidence.

Source: Rastogi 1996, Contact Dermatitis Link to this fact

Hidden ingredients / Self-reported survey

Only about 1 in 4 Germans (27.5%) know that fragrance chemicals do not have to be fully disclosed on a product's label or safety data sheet.

Moderate evidence: Awareness item, not a measurement of actual disclosure; Germany 2019, n=1,102.

Source: Klaschka 2020a, Environmental Sciences Europe Link to this fact

Hidden ingredients / Measured in people or real products

The chemical composition of all five fabric-softener dryer-sheet products tested was undisclosed (a trade secret); gas chromatography/mass spectrometry of one scented brand's emissions found only petroleum-derived aromatic compounds (toluene, styrene, xylenes, trimethylbenzene, isopropylbenzene) plus phenol and thymol — no fragrance terpenes, esters, or alcohols were detected, even though prior published analyses had found such compounds (limonene, linalool, benzyl acetate, and others) in fabric-softener emissions generally.

Moderate evidence.

Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact

Hidden ingredients / Journalism

Of the volatile organic compounds identified coming from the dryer vent and the laundry products' own headspace, only ethanol was listed on either product's label or Material Safety Data Sheet.

Moderate evidence: Restates the primary study's disclosure finding (Steinemann 2013); same underlying product as in the 2009 and 2011 Steinemann headspace papers, not an independent product.

Source: Kessler 2011 (EHP Forum), Environmental Health Perspectives Link to this fact

Hidden ingredients / Review of other studies

The word 'parfum' on a cosmetic ingredient list can stand for up to several hundred fragrance chemicals, so a consumer cannot tell whether fragrance allergens beyond the 26 EU-labeled ones are present.

Moderate evidence.

Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact

Hidden ingredients / Measured in people or real products

Most healthcare workers using disinfectants did not know whether the products they used contained quaternary ammonium compounds: 99 of 543 subjects (18.2%) could not be classified by exposure status from self-report alone, and researchers had to independently review Material Safety Data Sheets with 3 experts to determine actual product ingredients.

Moderate evidence.

Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact

Hidden ingredients / Other evidence

Reading a product's ingredient label does not tell a consumer whether a listed preservative has actually undergone an environmental risk assessment — that status depends on invisible regulatory classification (which EU regulation covers the product category) rather than on anything printed on the package, per a 2016 German household inventory study.

Moderate evidence: Inference from the paper's regulatory-coverage analysis, not a consumer-comprehension study.

Source: Wieck 2016, Environment International Link to this fact

Hidden ingredients / Measured in people or real products

When low-molecular-weight PTFE micropowder (the fine Teflon powder used as a filler and slip agent) is manufactured by gamma-irradiating PTFE in open air, it releases PFOA — a persistent 'forever chemical' — at levels that can exceed the EU's regulatory limit: 28.3 ppb measured after air irradiation, versus a 25 ppb REACH limit that took effect in July 2020.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

Even irradiating PTFE in a vacuum (no oxygen present) still produced up to 25.6 ppb of PFOA at higher radiation doses (400 kGy), right at the EU's regulatory limit, showing that removing atmospheric oxygen during manufacture reduces but does not eliminate PFOA formation.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

Gamma irradiation traps two kinds of free radicals inside PTFE — one at the broken ends of polymer chains, one within the chain — at roughly a 10:1 ratio; it is specifically the chain-end radicals reacting with oxygen and water after exposure to air that go on to form PFOA, while the more persistent in-chain radicals mostly do not.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

Hidden ingredients / Measured in people or real products

Besides PFOA, gamma-irradiated PTFE also released smaller amounts of related short-chain perfluorocarboxylic acids: about 46 ppb perfluorobutanoic acid (PFBA), 26 ppb perfluoropentanoic acid, 20 ppb perfluorohexanoic acid, and 15 ppb perfluoroheptanoic acid, and, when irradiated in an air-filled sealed bag, a wider range of these acids from 4 to 13 carbons.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

Hidden ingredients / Review of other studies

Unlike most retail candles labeled only "fragrance," the candles in this study had their full wax and fragrance formulations precisely known and reported, because they were purpose-built for the research with fragrance industry cooperation.

Moderate evidence.

Source: Salthammer 2021, Environment International Industry-funded Link to this fact

Hidden ingredients / Other evidence

A 1998 GC-MS survey of 71 European deodorants found 226 distinct fragrance and non-fragrance chemicals – more than ten times the 21 fragrance substances the same research group had specifically targeted and quantified in a companion study on the same products.

Moderate evidence: Single study, 1998 market snapshot (product formulations have changed since); no concentrations measured for any of the 226 chemicals, only presence/absence by product type.

Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact

Hidden ingredients / Other evidence

Methyl anthranilate, flagged by this 1998 GC-MS/SAR survey as an aromatic amine (a structural class linked to sensitization and other toxicity concerns), was found in 22 of 71 European deodorants tested, a chemical identity a fragrance label would not disclose since it is covered by the generic term 'parfum'.

Moderate evidence: Structural classification, not a clinical allergy finding for this specific compound in this paper; presence only, not concentration.

Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact

Hidden ingredients / Other evidence

Products labeled 'fragrance free' have been shown to still contain fragrance ingredients, used as preservatives, masking perfumes, or botanicals.

Moderate evidence: Secondary citation of Scheinman's clinical observations, not this review's own new data.

Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact

Hidden ingredients / Review of other studies

Fragrance in deodorants and antiperspirants often functions as a deliberate odor-masking ingredient at percent-level concentrations (e.g., linalool combined with dihydromyrcenol at 0.2-1% w/w, or a multi-fragrance blend of musk, skatole, lemon oil, lavender oil, jasmine, vanillin, benzoin, benzyl acetate, and menthol in one patented licorice-root deodorant), separate from and in addition to any anti-microbial active in the same product.

Moderate evidence.

Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact

Hidden ingredients / Review of other studies

Body odor intensity has a genetic component: people carrying the ABCC11 gene variant linked to dry earwax (common in East Asian populations) had less body odor and lower levels of the odor-carrier protein apolipoprotein D than people without it, in the study this review cites.

Moderate evidence.

Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact

Hidden ingredients / Lab study (cells or chemistry)

In a lab test of 25 commercial underarm deodorants, 9 (36%) showed measurable estrogen-like activity in a human breast-cancer-cell assay, concentrated almost entirely in sprays (7 of 10) versus roll-ons (1 of 9) and sticks (1 of 6) from the same product lines.

Moderate evidence.

Source: Lange et al. 2014, Chemosphere Link to this fact

Hidden ingredients / Lab study (cells or chemistry)

Testing 62 individually purchased fragrance-related ingredients found in the deodorants, 8 were estrogenic in the same cell assay – including the musk HHCB/galaxolide and benzyl salicylate – at potencies the study describes as comparable to parabens, a preservative class with well-documented weak estrogenic activity.

Moderate evidence.

Source: Lange et al. 2014, Chemosphere Link to this fact

Hidden ingredients / Measured in people or real products

Before candles were lit, the largest class of chemicals detected across the products was esters (30 of 34 dominant compounds identified), which manufacturers disclose on the label only as 'fragrance' or 'aroma oil.'

Moderate evidence.

Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact

Hidden ingredients / Measured in people or real products

329 of 5,588 fragranced cosmetic products (5.9%) named one or more of the 26 EU fragrance allergens on the ingredient list without the words 'parfum', 'fragrance' or 'aroma' also appearing on the label; 45 of these 329 (13.7%) were marketed with 'organic/eco', 'sensitive', 'pure' or 'natural' in the product name.

Moderate evidence: Label survey; whether this reflects deliberate omission or labeling inconsistency by the manufacturer is not determined.

Source: Bennike 2017/2018 Link to this fact

Hidden ingredients / Measured in people or real products

In a 2018 Korean government survey of 482 market deodorants, 18 of 26 screened fragrance allergens and 13 of 27 screened biocidal ingredients were actually detected in the products; some fragrance ingredients reached extreme concentrations in individual products, including benzyl benzoate at 142,344 mg/kg (about 14% of product weight) and thymol at 271,525 mg/kg (about 27% of product weight).

Moderate evidence: Single Korean-market survey (64-482 products depending on the ingredient panel); concentrations are maxima found in specific products, not typical or average levels.

Source: Kim et al. 2018, Science of The Total Environment Link to this fact

Hidden ingredients / Other evidence

Even "unscented" or "fragrance-free" products may contain a perfume or essential oil added specifically to mask the unpleasant odor of the product or its other ingredients.

Moderate evidence: General statement in a narrative review, not a count of how many fragrance-free-labeled products actually contain a masking fragrance.

Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact

Hidden ingredients / Review of other studies

In the EU, an entire perfume or fragrance composition can be declared on the ingredient list as the single word 'parfum' or 'aroma', legally hiding every chemical in it except the handful of allergens that must be named separately.

Moderate evidence: Restates the regulation's text; not new data, and the same point is made by other evidence base sources.

Source: Tegengif 2022 Link to this fact

Hidden ingredients / Advocacy group testing

Auditing the printed ingredient lists of 20 popular perfumes sold in Belgium, Denmark, and the Netherlands against 13 official and NGO hazard lists (EDC lists, EU harmonized classifications, the SVHC candidate list, the EU fragrance-allergen list, environmental-persistence lists) turned up 26 problematic substances across the 20 products.

Moderate evidence.

Source: Tegengif 2022 Link to this fact

Hidden ingredients / Advocacy group testing

Only 2 of the 20 tested perfumes contained no suspected endocrine-disrupting chemical (EDC) on their declared ingredient list; the other 18 contained at least one.

Moderate evidence: Counts declared ingredients only; a perfume could contain additional undisclosed EDCs hidden under 'Parfum'.

Source: Tegengif 2022 Link to this fact

Hidden ingredients / Animal study

GC-MS of the scented candle's emissions detected methylene chloride (2.71% of peak area, a carcinogen with two known toxic-metabolite pathways) and the phthalate DEHP (0.1%), neither of which would appear on a candle's fragrance or wax label.

Moderate evidence.

Source: Mohamed et al. 2025, Frontiers in Public Health Link to this fact

Hidden ingredients / Measured in people or real products

FDA's 2010 follow-up testing of 84 consumer cosmetic products found the fragrance solvent diethyl phthalate (DEP) in all 11 fragrance products tested (up to 36,006 ug/g, about 3.6% by weight) and in 20 of 60 adult-use products overall, while dibutyl phthalate (DBP) was found only in nail products (11 of 24, up to 62,607 ug/g), even though phthalates carried in as part of 'fragrance' are not required to be named on the label.

Moderate evidence.

Source: Hubinger 2010, Journal of Cosmetic Science Link to this fact

Hidden ingredients / Government agency

The report states that the vast majority of chemicals in current commercial use have never been tested at all for endocrine-disrupting activity, and that unlike active ingredients in pharmaceuticals and pesticides, most materials, articles, and consumer goods are not required to declare their full chemical make-up, leaving many sources of hormone-disrupting exposure simply unknown.

Moderate evidence: General statement about global chemical commerce as a whole, not a count or rule specific to fragrance or personal-care ingredients.

Source: WHO/UNEP 2012 Link to this fact

Hidden ingredients / Review of other studies

"Alum stone" deodorants are potassium alum (Al3K(SO4)2, 12H2O), which does contain aluminum, sometimes marketed under the name "potassium alum" or the misleading "double potassium sulfate," which omits the word aluminum entirely.

Moderate evidence: Single review's characterization of marketing language, not a systematic label survey.

Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact

Hidden ingredients / Measured in people or real products

Hormone-disrupting chemicals in household cleaners, synthetic detergents, fabric softeners, air fresheners, and deodorants are almost always added as fragrance or preservative, not as the product's main ingredient, so their presence rarely shows up as a headline ingredient a shopper would notice.

Moderate evidence: Based on a database of listed ingredients matched to EPA hazard flags, not chemical measurement of the actual products; a single country's product registry (South Korea, 2020).

Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact

Hidden ingredients / Measured in people or real products

Certain hormone-disrupting chemicals recur together on the same product's ingredient list more often than chance: benzisothiazolinone with hexyl cinnamaldehyde in synthetic detergents, and the fragrance chemical Lilial (butylphenyl methylpropional) with citronellol in fabric softeners, identified by mining co-occurrence patterns across thousands of Korean household products.

Moderate evidence: Association-rule mining measures how often chemicals are listed together on ingredient lists, not their combined toxicity or exposure when the product is used.

Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact

Hidden ingredients / Government agency

DEA and its condensates (cocamide DEA, lauramide DEA) are not banned from cosmetics, but US Cosmetic Ingredient Review guidance says they should not be combined with nitrite or other nitrosating agents in a formulation, because that reaction can form N-nitrosodiethanolamine (NDELA), an animal carcinogen that is not itself listed on any ingredient label.

Moderate evidence.

Source: Kraeling 2004, Food and Chemical Toxicology Link to this fact

Hidden ingredients / Measured in people or real products

A 2007 NRDC test found one or more of five phthalate esters (DBP, DEP, DIBP, DIHP, DMP) in 12 of 14 US air fresheners, including some labeled all-natural or unscented, and none of the 12 positive products listed phthalates as an ingredient on the label.

Moderate evidence.

Source: EPA 2007, citing NRDC 2007 Link to this fact

Hidden ingredients / Measured in people or real products

In the 2007 NRDC air-freshener test, diethyl phthalate (DEP) was the phthalate found at the highest concentrations: three samples at 360, 1,100 and 7,300 ppm, and six more samples at 6.3 ppm or less; di-n-butyl phthalate (DBP), the only one of the five on California's Proposition 65 reproductive-toxicity list, was found at much lower levels (four samples under 1 ppm, one at 4.5 ppm).

Moderate evidence.

Source: EPA 2007, citing NRDC 2007 Link to this fact

Hidden ingredients / Government agency

Benzophenone migrates into food from UV-cured printing inks on paperboard packaging even without direct contact — including through frozen storage at -20C and via the vapor phase from secondary packaging — and the UK Food Standards Agency estimated high-level adult dietary exposure at 1.2-1.5 micrograms/kg body weight per day.

Moderate evidence: Exposure estimate combines a 97.5th-percentile high-consumption food-frequency scenario with average measured occurrence levels, not a direct biomonitoring measurement.

Source: IARC 2013 Link to this fact

Hidden ingredients / Measured in people or real products

Styrene migrates from polystyrene food-contact packaging into food; US dietary intake from this route has been estimated at roughly 9 micrograms per day (Lickly et al. 1995), with strawberries and avocados showing the highest detected styrene concentrations in an FDA Total Diet Study of 70 foods.

Moderate evidence.

Source: IARC 2019 (Vol. 121) Link to this fact

Hidden ingredients / Government agency

EPA lists moth repellents and air fresheners among household-product sources of organic-gas (VOC) indoor air pollution, and notes that paradichlorobenzene, a chemical carrying an 'avoid breathing vapors' warning on moth-repellent labels, is also the key active ingredient in many air fresheners.

Moderate evidence: EPA names the shared ingredient and the moth-repellent warning; it does not separately assess air-freshener-specific health risk.

Source: US EPA, "The Inside Story" Link to this fact

Hidden ingredients / Measured in people or real products

In a database analysis of Korean household chemical products, the most prevalent chemicals flagged as endocrine disruptors were compounds added as fragrance ingredients or preservatives (e.g. linalool, D-limonene, hexyl cinnamaldehyde), not the product's main functional ingredient.

Moderate evidence.

Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact

Hidden ingredients / Measured in people or real products

Diethyl phthalate (DEP), the phthalate most often found in fragrance products, most likely comes from the fragrance ingredient itself, where it functions as a solvent and fixative rather than from another use in the formulation.

Moderate evidence.

Source: Hubinger & Havery 2006, Journal of Cosmetic Science Link to this fact

Hidden ingredients / Review of other studies

An FDA laboratory survey concluded that phthalate esters found in most cosmetic products most likely enter via the fragrance ingredient itself, where they function as a solvent/fixative rather than for some other purpose.

Moderate evidence.

Source: Hubinger & Havery 2006, Journal of Cosmetic Science Link to this fact

Indoor air / Self-reported survey

19.4% of Australians reported health problems from being near someone wearing fragrance and 16.4% from air fresheners.

Moderate evidence: Self-report; no exposure measurement; counts 213/1,098 and 180/1,098 confirmed in Steinemann 2018 (MCS, AU) Table 2, same dataset.

Source: Steinemann 2017, Preventive Medicine Reports Link to this fact

Indoor air / Self-reported survey

About 1 in 6 adults (17%) in four countries said air fresheners or deodorizers make them unwell; of those, half reported breathing problems.

Moderate evidence: Self-report, no objective measure.

Source: Steinemann 2019, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Self-reported survey

41% of US adults with asthma reported health problems from air fresheners, and 36.7% said they can't use a public restroom that has one.

Moderate evidence: Self-report.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Self-reported survey

23.5% of Swedes reported health problems from being near someone wearing a fragranced product.

Moderate evidence: Self-report.

Source: Steinemann 2018 (Sweden), Air Quality, Atmosphere & Health Link to this fact

Indoor air / Self-reported survey

About 1 in 5 US adults (20.4%) reported health problems from air fresheners, and 23.6% from being near someone wearing a fragranced product.

Moderate evidence: Self-report; no exposure measurement.

Source: Steinemann 2016, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Self-reported survey

About 1 in 5 Australians with asthma (21.4%) said they can't or won't use public toilets that have air fresheners.

Moderate evidence: Self-report.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Measured in people or real products

Scented laundry products put fragrance chemicals into outdoor air: in two homes, limonene (a citrus scent chemical) came out of the dryer vent only when fragranced detergent or dryer sheets were used (up to 14.7 ug/m3), not in the no-product runs.

Moderate evidence.

Source: Steinemann 2013, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Measured in people or real products

In a room-sized test chamber, mopping with a pine-oil cleaner or spraying an orange-oil degreaser, with ozone at typical summer-smog levels, produced 130-280 µg/m³ of fine particles, versus 2-5 µg/m³ when the same products were used without ozone.

Moderate evidence.

Source: Singer 2006, Atmospheric Environment Link to this fact

Indoor air / Measured in people or real products

Scent chemicals in cleaners and air fresheners react with ozone that drifts in from outdoors to make formaldehyde: cleaning raised formaldehyde by 9-16 ppb for 4 hours, and a plug-in air freshener raised it by about 6 ppb for as long as it ran.

Moderate evidence.

Source: Singer 2006, Atmospheric Environment Link to this fact

Indoor air / Measured in people or real products

After 2-7 minutes of cleaning with a terpene cleaner, indoor air chemistry stayed altered for 10-12 hours because the scent chemicals soaked into walls and floors and came back out.

Moderate evidence.

Source: Singer 2006, Atmospheric Environment Link to this fact

Indoor air / Measured in people or real products

In a European study that measured the air 182 adults actually breathed over 48 hours, exposure to pine- and citrus-type scent chemicals from cleaning products and fragrances rose with the number of children at home (3-carene median 0.9 to 2.5 µg/m³); the authors attribute this to more cleaning.

Moderate evidence: Late-1990s, small subgroups, attribution to cleaning is the authors' inference; CEFIC-LRI co-funded.

Source: Edwards 2006, Atmospheric Environment Industry-funded Link to this fact

Indoor air / Self-reported survey

Air fresheners were the most common secondhand trigger: 15.5% of UK adults reported health problems from them, and 12.1% avoid or are reluctant to use public restrooms that have them.

Moderate evidence: Self-report.

Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Measured in people or real products

Keeping a gel air freshener in a car raised the fragrance chemical limonene in the air the driver breathed 3.6-4.7 times, to about 19-28 ug/m3, during real commutes (10 cars tested).

Moderate evidence: N=5 per group, non-randomized; mostly drivers' own products.

Source: Jo 2008, Chemosphere Link to this fact

Indoor air / Measured in people or real products

In lab tests, gel air fresheners released limonene at up to 1.5 mg per hour, far more than any other chemical measured.

Moderate evidence.

Source: Jo 2008, Chemosphere Link to this fact

Indoor air / Measured in people or real products

Indoors, vapors from these products run about 7 times higher than outdoors, and include fragrance chemicals such as limonene.

Moderate evidence: Box model checked against indoor measurements.

Source: McDonald 2018, Science Link to this fact

Indoor air / Measured in people or real products

Mopping a room with a terpene-based (pine- or citrus-type) cleaner caused bursts of tiny new particles, about 100 times the particle count of outdoor air, as the scent chemicals reacted with ozone.

Moderate evidence.

Source: Rosales 2022, Science Advances Link to this fact

Indoor air / Measured in people or real products

During mopping with a terpene cleaner, scent chemicals such as limonene and pinene peaked at 280-380 ppb in the room air.

Moderate evidence.

Source: Rosales 2022, Science Advances Link to this fact

Indoor air / Measured in people or real products

Homes painted, refurnished, or re-floored in the previous 6 months had higher levels of indoor chemicals released into the air (including toluene and xylenes) than other homes.

Moderate evidence: Not a fragrance finding.

Source: Maisey 2013, Atmospheric Environment Link to this fact

Indoor air / Measured in people or real products

For the third of homes using p-dichlorobenzene products, the upper-bound cancer risk was about 3x the population average (~270 vs 90 in a million).

Moderate evidence: Upper-bound 1991 potencies, 7-10x above best estimates.

Source: Wallace 1991, Environmental Health Perspectives Link to this fact

Indoor air / Measured in people or real products

A limonene-scented foam cleaner released formaldehyde, an irritant and carcinogen, both directly and through reactions with ozone after use.

Moderate evidence.

Source: Rossignol 2013, Atmospheric Environment Link to this fact

Indoor air / Measured in people or real products

Scent was only part of what a scented cleaner released: its glycol-ether solvent reached about 1,100 ug/m3 in room air against 71 ug/m3 for limonene.

Moderate evidence.

Source: Rossignol 2013, Atmospheric Environment Link to this fact

Indoor air / Review of other studies

Average indoor formaldehyde in homes exceeded California's long-term health limit (9 µg/m³) in every European country the EU's own researchers assessed.

Moderate evidence: Secondary data; formaldehyde mainly from building materials, not shown to be from fragrance.

Source: Sarigiannis 2011, Environment International Link to this fact

Indoor air / Review of other studies

EU researchers attributed large swings in home limonene levels within the same city to whether people had used a fragrance, air freshener, or cleaning product before the air was sampled.

Moderate evidence.

Source: Sarigiannis 2011, Environment International Link to this fact

Indoor air / Review of other studies

The standard week-long air tests used across Europe miss the short spikes of chemicals released after cleaning, which could change the risk picture for eye and airway irritation.

Moderate evidence: Authors' methodological caveat, not a measured result.

Source: Sarigiannis 2011, Environment International Link to this fact

Indoor air / Lab study (cells or chemistry)

In lab chamber tests set up to mimic a room, the citrus scent chemical limonene reacted with ozone in the air to form fine particles carrying reactive oxygen species.

Moderate evidence.

Source: Chen & Hopke 2010, Indoor Air Link to this fact

Indoor air / Lab study (cells or chemistry)

Limonene produced 2 to 11 times more of these reactive particles than alpha-pinene, the pine scent chemical.

Moderate evidence: Chamber comparison only.

Source: Chen & Hopke 2010, Indoor Air Link to this fact

Indoor air / Government agency

EPA notes that people using products can expose themselves and others to very high pollutant levels, and that elevated levels can persist in the air long after the activity ends.

Moderate evidence: About product use in general; the peak example given is paint stripping (up to 1,000x outdoor), not fragrance.

Source: US EPA 2026 Link to this fact

Indoor air / Measured in people or real products

In an office-sized test room with some ozone in the air, a single ordinary spray of perfume, body spray, or hair spray, or a dab of hand lotion, set off a burst of new ultrafine particles within minutes, reaching 34,000–200,000 particles per cubic centimeter, more than in many city streets.

Moderate evidence: One chamber, 5 products, one use each; ozone held at 35–40 ppb (high end for indoors); masked volunteer; no toxicity measured.

Source: Wu 2024, Environmental Science & Technology Letters Link to this fact

Indoor air / Measured in people or real products

Almost everything in a perfume ends up in the air: one perfume released 964 mg of vapor per gram used, mostly alcohol but also about 32 mg per gram of terpene fragrance chemicals.

Moderate evidence: One perfume; emission factors are lower bounds (PTR-MS blind to some compounds).

Source: Wu 2024, Environmental Science & Technology Letters Link to this fact

Indoor air / Measured in people or real products

Skipping showers for one or two days raised skin-derived acetic acid emissions by 84% and 172%, and increased the products of ozone reacting with skin.

Moderate evidence: 4 men; bacterial origin of the acids is inferred, not measured; fragrance-free soap/shampoo used throughout.

Source: Wang 2024, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

Pure limonene only irritates human eyes at about 445 mg/m³, far above indoor levels. A limonene-ozone mixture reacted for just 10 minutes raises eye-blink rates at roughly 1,000-2,000x less limonene: Klenø & Wolkoff (2004, n=8, primary) found residual 0.42 mg/m³ limonene + 0.08 mg/m³ ozone raised blink frequency 42% (P<0.0001); Nøjgaard (2005, n=10, primary) found a lower dose, 0.23 mg/m³ limonene + 0.08 mg/m³ ozone, gave a smaller but still significant +17% (p=0.003).

Moderate evidence.

Source: Wolkoff 2013, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Other evidence

In mouse tests, about three-fourths of the airway irritation from limonene reacting with ozone came from formaldehyde and residual limonene together (formaldehyde the dominant contributor, at roughly 17-22 percentage points; residual limonene a small but real contributor, under 5 percentage points), not from the particles.

Moderate evidence.

Source: Wolkoff 2013, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Review of other studies

An indoor-air toxicologist recommends measuring limonene in offices because this common fragrance 'easily undergoes ozonolysis producing oxidation products that includes formaldehyde'.

Moderate evidence.

Source: Wolkoff 2013, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Measured in people or real products

Indoor ozone reacts with the natural oils on our skin. In a test room with four people and 35 ppb ozone, this alone kept highly reactive hydroxyl (OH) radicals at about 7×10⁵ per cm³, similar to levels measured in empty rooms after cleaning with pine or citrus products.

Moderate evidence.

Source: Zannoni 2022, Science Link to this fact

Indoor air / Measured in people or real products

OH radicals attack almost every organic chemical in indoor air, not only the ~10% that ozone reacts with, and these reactions happen in the air closest to our bodies; the researchers note that many of the resulting products have never been tested for toxicity.

Moderate evidence: No toxicity or health endpoint measured; the 'untested' statement is the authors' assessment.

Source: Zannoni 2022, Science Link to this fact

Indoor air / Instrument measurement

The 'air quality index' on home air monitors is driven by particles; it did not move when only solvent-type products (nail polish remover, hair dye) were used, even though the VOC reading rose.

Moderate evidence: One unnamed device; its AQI does not follow the US EPA scale.

Source: Grigoryants 2025, Cureus Link to this fact

Indoor air / Journalism

In 2003 Southern California air regulators estimated that household and small-business products, including cleaners, cosmetics, perfume, and room fresheners, released about 108 tons of smog-forming chemicals a day in the Los Angeles region, second only to vehicle tailpipes.

Moderate evidence: Agency inventory relayed by the LA Times; for measured/modeled figures use McDonald 2018 (LA) and Coggon 2021 (NYC 2018: VCPs comparable to vehicle fuels for ozone).

Source: DONTSPRAYCALIFORNIA 2008 (DOJ ADA docket) Link to this fact

Indoor air / Measured in people or real products

A new Little Tree car air freshener releases most of its limonene in the first few days: in a closed car the limonene signal halved roughly every day and was nearly gone within 4-5 days.

Moderate evidence: Relative peak areas only, no concentrations; one car and one scent; baseline not shown.

Source: Pino-Delgado 2021 (J Student Res), Journal of Student Research Link to this fact

Indoor air / Self-reported survey

Among Australians with diagnosed multiple chemical sensitivities, about three in four (77.5%) said a fragranced product had kept them from going somewhere, and about two in three (64.8%) can't or won't use public toilets with air fresheners.

Moderate evidence.

Source: Steinemann 2018, Preventive Medicine Reports Link to this fact

Indoor air / Measured in people or real products

When 40 ppb of ozone was added to a room holding a mix of 23 common indoor chemicals, including the citrus and pine scent chemicals limonene and alpha-pinene, formaldehyde tripled (13 to 40 µg/m³), ultrafine particles rose about 18-fold (2,500 to 46,000 per cm³) and particle mass reached 140 µg/m³.

Moderate evidence: Chamber with VOC load ~10x typical buildings; 23-compound office mixture, not a fragranced product; other alkenes also react.

Source: Fiedler 2005, Environmental Health Perspectives Link to this fact

Indoor air / Self-reported survey

Among US adults reporting diagnosed multiple chemical sensitivity, 59% said they could not use a public restroom with an air freshener and 70% had been kept from going somewhere by fragranced products.

Moderate evidence.

Source: Steinemann 2018 (JOEM), Journal of Occupational and Environmental Medicine Link to this fact

Indoor air / Measured in people or real products

When moisturizer goes on the face, the wearer breathes a short burst of its vapors (alcohol, fragrance terpenes, benzyl alcohol) that room-air monitoring does not capture; at a mannequin's nose, alcohols and terpenes took about 30 minutes to fade and some solvents up to 2.5 hours.

Moderate evidence: Mannequin head, no people; unheated face (21 °C vs 32–34 °C skin) and a 5-ACH lab; the size of the burst is disputed (tabulated doses do not match the plotted traces).

Source: Yeoman 2022, Indoor Air Link to this fact

Indoor air / Measured in people or real products

With four people in a test room and indoor ozone at about 35 ppb, the chemical reactivity of the air roughly tripled once ozone was added (from about 8–11 to 25–35 per second). Almost all of the increase came from carbonyls made when ozone hit the natural oils on skin, and across the whole study ozone explained 85% of the variation.

Moderate evidence: One chamber (22.5 m³, 3.2 h⁻¹, mixing fans), one ozone level tested on/off; no health endpoint; fragrance-free products used throughout.

Source: Zannoni 2021, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

Wearing shorts and t-shirts instead of long clothes raised the skin-ozone products 6-MHO, 4-oxopentanal, and geranyl acetone by 35–51%. Clothes that had been worn for a few hours took up ozone about as fast as bare skin, because skin oil moves into the fabric.

Moderate evidence: One group of 4 young adults, ~35 ppb ozone; chemistry only; 6-MHO values may be inflated by an inlet artifact.

Source: Zannoni 2021, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

A dried film of pine-oil cleaner or orange-oil degreaser, with its scent chemicals already evaporated away, still produced formaldehyde and a burst of new particles when later exposed to ozone.

Moderate evidence: Single glass-plate surface test per product in a lab chamber, not tested on real room surfaces (carpet, fabric, furniture).

Source: Destaillats 2006, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

Wiping a small kitchen table with a few grams of an ordinary spray cleaner put 270-2,300 ug/m3 of the solvent 2-butoxyethanol into the air of a room-sized test chamber for the next hour; four of five cleaners tested contained it.

Moderate evidence: 50 m3 empty chamber, use rate at the ~84th percentile of observed users; real furnished rooms sorb glycol ethers faster, lowering peaks.

Source: Singer 2006, Indoor Air, Indoor Air Link to this fact

Indoor air / Measured in people or real products

Cleaning with a pine-oil or citrus cleaner raised scent chemicals (limonene, terpinolene, alpha-terpineol) to about 1,000-6,000 ug/m3 for the first hour in a room-sized chamber, and some stayed elevated for many hours afterwards.

Moderate evidence: Empty chamber; one product per formulation; alpha-terpineol's persistence depends on surface water films and towels left in the room.

Source: Singer 2006, Indoor Air, Indoor Air Link to this fact

Indoor air / Measured in people or real products

A plug-in scented-oil air freshener evaporated 1.5 g of product a day and kept its scent chemicals at 30-160 ug/m3 in the room over three days; its two largest emissions were fragrance esters (bornyl and benzyl acetate, 280-410 ug/m3), not the ozone-reactive terpenes usually studied.

Moderate evidence: One plug-in product; a different air-freshener type (e.g. limonene-selected gels, Jo 2008) can be limonene-dominant instead.

Source: Singer 2006, Indoor Air, Indoor Air Link to this fact

Indoor air / Measured in people or real products

Leaving used paper towels in the room after cleaning increased the solvent and scent chemicals released by 35-100%.

Moderate evidence: Measured over 24 h in an empty chamber.

Source: Singer 2006, Indoor Air, Indoor Air Link to this fact

Indoor air / Measured in people or real products

Scented spray products — spray and plug-in air fresheners, dusting sprays — were among the specific product types most strongly associated with childhood wheeze and asthma risk in this Canadian birth cohort.

Moderate evidence.

Source: Parks et al. 2020, CMAJ (Canadian Medical Association Journal) Link to this fact

Indoor air / Measured in people or real products

When the same volunteers breathed through a mask into a separate room, so only their breath (not their skin) was in contact with the air, indoor ozone barely changed at all — showing the ozone-removing chemistry happens on skin and clothing, not from exhaling.

Moderate evidence: Based on a single experiment (Experiment 12) in the ICHEAR chamber; not replicated across groups.

Source: Bekö 2020, Indoor Air Link to this fact

Indoor air / Test-chamber measurement

A car air freshener's own terpenes (alpha-pinene, beta-pinene, p-cymene, limonene) react with in-vehicle ozone to form ultrafine particles and irritant gases (formaldehyde, acetaldehyde, acrolein) that never appear on the product's ingredient list, because they are made in the cabin air, not sold in the bottle.

Moderate evidence.

Source: Lamorena & Lee 2008 (J Hazard Mater), Journal of Hazardous Materials Link to this fact

Indoor air / Measured in people or real products

In a real working primary school, mopping a classroom with a limonene-containing detergent produced bursts of tens of thousands of tiny new particles per cubic centimeter within minutes, but only when ozone was present in the air; a plain water-only mop produced no such burst.

Moderate evidence.

Source: Morawska 2009, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

A limonene-cleaning event needs indoor ozone above roughly 5 parts per billion to trigger a detectable burst of new ultrafine particles; below that threshold, in this study's controlled trials, essentially no particle formation occurred.

Moderate evidence.

Source: Morawska 2009, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

Nearly all (93%) of the DC childcare facilities studied used chlorine bleach to sanitize surfaces, and chloroform (a bleach byproduct classified by IARC as possibly carcinogenic to humans, Group 2B) was detected in 100% of air samples; the authors attribute it mainly to bleach use.

Moderate evidence: Association, not a measured reaction; bleach usage self-reported, chloroform sources not otherwise investigated.

Source: Quirós-Alcalá 2016, Environmental Research Link to this fact

Indoor air / Measured in people or real products

Among 3,411 Czech households with an infant, the most commonly used chemical products were window cleaner (88%), deodorant (82%) and aerosol/hairspray products (74%) — not air fresheners, which were the second-least-used of 18 chemical product categories (26%).

Moderate evidence: Self-reported product use frequency, one Central European cohort; product prevalence does not equal exposure dose or emission rate.

Source: Mikeš 2019, Science of the Total Environment Link to this fact

Indoor air / Measured in people or real products

A 10-minute-old reacted mixture of limonene and ozone (residual 75 ppb limonene + 40 ppb ozone) raised human eye-blink frequency 42% relative to clean air, while the same men's eyes exposed separately to just limonene, or just ozone, at similar or higher levels, did not blink more.

Moderate evidence.

Source: Klenø & Wolkoff 2004 Link to this fact

Indoor air / Review of other studies

The four most common airborne fragrances in homes and offices — pinene, limonene, linalool, and eugenol — are usually present at levels 2 to 3 times below the concentration needed to physically irritate the eyes and airways, but at or above the much lower level needed just to smell them.

Moderate evidence.

Source: Wolkoff & Nielsen 2017, Environment International Link to this fact

Indoor air / Measured in people or real products

In the two largest, most realistic human tests to date, breathing a fragrance-and-ozone reaction mixture (the kind formed when a citrus-scented product meets indoor ozone) produced no measurable increase in eye, nose or throat irritation, in either healthy people, or asthmatics.

Moderate evidence.

Source: Wolkoff & Nielsen 2017, Environment International Link to this fact

Indoor air / Animal study

A Danish government toxicology lab derived a specific reference value for 4-oxopentanal (4-OPA), a common byproduct when ozone reacts with skin oils and fragrance terpenes indoors: 30 ppb (123 ug/m3), from mouse bronchoconstriction data with standard safety margins applied. Measured office and aircraft-cabin 4-OPA levels (2-10 ppb) sit below this value, though ventilation-filter and occupied-room measurements (up to 10-16 ppb) come closer.

Moderate evidence.

Source: Wolkoff et al. 2012/2013, Toxicology Letters Link to this fact

Indoor air / Animal study

Of five common ozone-terpene reaction products tested in mice (4-AMCH, dihydrocarvone, IPOH, 6-MHO, and 4-OPA), the study's own conclusion was that four do not contribute substantially to airway irritation at indoor or ambient concentrations; only IPOH (sensory irritation) and 4-OPA (airflow limitation) were flagged as compounds of concern warranting precaution against excess formation.

Moderate evidence: Single animal study, one lab (NRCWE Copenhagen); precautionary conclusion, not evidence that current indoor exposure causes harm.

Source: Wolkoff et al. 2012/2013, Toxicology Letters Link to this fact

Indoor air / Measured in people or real products

In a study of 25 UK homes using real whole-air canister sampling (not a lab chamber), the scent chemicals D-limonene and alpha-pinene were the single most abundant VOC measured in 94% of homes, regardless of building age, size, or occupancy.

Moderate evidence.

Source: Wang 2017, Environmental Science: Processes & Impacts Link to this fact

Indoor air / Measured in people or real products

The UK home with the heaviest, most frequent use of cleaning and fragranced products (9 different products, some used more than 10 times in a week, plus a scented candle) had a 5-day average D-limonene concentration of up to 1,439 ug/m3, around 80 times the study's median home and possibly the highest domestic value reported in the literature at the time.

Moderate evidence: Single home out of 25 driving the extreme; 5-day average, not a short-term peak, which the authors state was likely higher.

Source: Wang 2017, Environmental Science: Processes & Impacts Link to this fact

Indoor air / Measured in people or real products

A personal-care product containing the silicone D5 (such as a deodorant applied hours earlier) can raise D5 levels inside a car far above outdoor background, and this passenger-carried D5 vents out of the car and mixes with the vehicle's exhaust-associated emissions when the cabin fan runs.

Moderate evidence.

Source: Coggon 2018, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

In a study of 60 UK homes with real air sampling (not a lab chamber), the VOC found in the highest concentration indoors was n-butane, an aerosol-spray propellant, not a fragrance chemical; it reached a wintertime maximum of 4,630 ug/m3, and aerosol antiperspirant/deodorant was the single most universally used VOC-releasing product, used in all 60 homes.

Moderate evidence: One UK town's panel-recruited cohort (Ashford, Kent); Givaudan-funded (fieldwork), analysis independent at University of York.

Source: Heeley-Hill 2021, Environmental Science: Processes & Impacts Industry-funded Link to this fact

Indoor air / Measured in people or real products

Indoor VOC levels exceeded outdoor levels in the large majority of homes studied — 84% in summer and 100% in winter — confirming that for this cohort, indoor air, not outdoor air, was the dominant source of VOC exposure.

Moderate evidence: Outdoor samples were not individually paired with every indoor home/period; mean seasonal outdoor values used for comparison.

Source: Heeley-Hill 2021, Environmental Science: Processes & Impacts Industry-funded Link to this fact

Indoor air / Measured in people or real products

Even with daily diary records of exactly how often 60 households used 13 different types of scented and cleaning products over three days, how often people used these products did not predict how much VOC was in their home's air (R-squared less than 0.001 for total VOC; no individual VOC, including limonene, showed a significant relationship).

Moderate evidence: Frequency of use, not dose per use or product formulation, was recorded; a narrow, weak exception existed for limonene with insecticide/plug-in-air-freshener use specifically.

Source: Heeley-Hill 2021, Environmental Science: Processes & Impacts Industry-funded Link to this fact

Indoor air / Animal study

In a mouse study, when scientists physically separated the invisible ultrafine particles from the gas fumes made by citrus-scent limonene reacting with ozone, the airway-irritating effect disappeared entirely, showing it's the gas products, led by formaldehyde, that irritate, not the particles themselves.

Moderate evidence.

Source: Wolkoff et al. 2008, Toxicology Letters Link to this fact

Indoor air / Animal study

In the same mouse study, formaldehyde formed by the limonene-ozone reaction, together with the leftover limonene itself, accounted for roughly three-quarters of the airway-irritating effect measured; formaldehyde was the dominant contributor.

Moderate evidence.

Source: Wolkoff et al. 2008, Toxicology Letters Link to this fact

Indoor air / Measured in people or real products

Dryer-vent air carried far more of the citrus-scent chemical D-limonene when households used fragranced laundry detergent (2.35-118 ug/m3, mean 33.34) than when they used fragrance-free detergent (0.13-1.50 ug/m3 after switching; 0.24-0.26 ug/m3 in households that never used fragranced detergent).

Moderate evidence.

Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Measured in people or real products

Switching to fragrance-free laundry detergent also reduced D-limonene in the laundry room's own indoor air, not just at the dryer vent, by up to 72.7% (mean 45.8%) within one month.

Moderate evidence: 4 households, single background-air sample per round, no statistical testing.

Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Measured in people or real products

Every one of 25 fragranced laundry products tested (US and Australian detergents and dryer sheets) emitted a terpene fragrance chemical (such as limonene, alpha-pinene, or eucalyptol), while none of 10 fragrance-free laundry products emitted any terpene at all.

Moderate evidence.

Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact

Indoor air / Other evidence

The 25 mg/m3 total-VOC chamber dose that produced a measurable lung-function decline in asthmatics is, in the authors' own framing, a maximal concentration seen in new houses but only a moderate one in the work environment — not a typical existing-home level.

Moderate evidence: This is the paper's own characterization of the dose, not a broad survey of home VOC levels for our cross-paper comparison.

Source: Harving et al. 1991, American Review of Respiratory Disease Link to this fact

Indoor air / Other evidence

The 25 milligram per cubic meter total-VOC chamber dose used in this and related studies to demonstrate airway inflammation is representative of a new home or office (i.e., freshly built or renovated), not of typical existing homes, which run far lower.

Moderate evidence.

Source: Koren et al. 1992, Archives of Environmental Health: An International Journal Link to this fact

Indoor air / Other evidence

Methacrolein, a reaction product of ozone and isoprene (a natural component of human breath), can form indoors or in the airway itself whenever an ozone source is present, with no fragrance or cleaning product needed.

Moderate evidence.

Source: Larsen & Nielsen 2000, Toxicology Letters Industry-funded Link to this fact

Indoor air / Other evidence

The one real-world indoor measurement of gas-phase methacrolein in the wiki (309 ng/m3, during ozone-terpene cleaning-product chemistry) sits about 2,800 times below this paper's own proposed occupational exposure limit for methacrolein, and about 96,000 times below the mouse RD50.

Moderate evidence.

Source: Larsen & Nielsen 2000, Toxicology Letters Industry-funded Link to this fact

Indoor air / Animal study

One fabric-softener pad left for 24 hours in a small, nearly sealed room (about 5 cubic meters, essentially no forced ventilation) raised bulk air TVOC to only 130 ppm — far below the same pad's raw emissions in a closed test chamber (190-750 ppm) — yet still caused significant sensory irritation in exposed mice (61% of breaths).

Moderate evidence.

Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact

Indoor air / Test-chamber measurement

A 21-chemical VOC mixture modeled on indoor air caused dose-related increases in respiratory, eye, and other symptoms in 15 healthy adults, worsening as the chamber concentration rose from 25 to 50 mg/m3 over 4-hour exposures.

Moderate evidence: Both tested concentrations (25 and 50 mg/m3) are roughly 100-1,000x higher than typical home indoor-air VOC levels, so this does not show ordinary indoor air causes these symptoms.

Source: Pappas et al. 2000, Int J Occup Environ Health 6:1-8 Link to this fact

Indoor air / Test-chamber measurement

In a chamber test at a realistic indoor ozone level (~40 ppb), adding ozone to an indoor-representative mixture containing the fragrance terpenes d-limonene and alpha-pinene generated formaldehyde (13 to 40 micrograms per cubic meter), several other irritant aldehydes, organic acids, and fine secondary particle pollution (140 micrograms per cubic meter, versus under 5 without ozone).

Moderate evidence.

Source: Fan et al. 2003, Environmental Science & Technology Link to this fact

Indoor air / Test-chamber measurement

Removing just the two fragrance terpenes (d-limonene and alpha-pinene) from the 23-chemical mixture, while keeping ozone and the other 21 chemicals, collapsed the secondary particle pollution to background levels (2-7 micrograms per cubic meter) and eliminated most of the irritant aldehydes — identifying these two terpenes as the drivers of essentially all the ozone-initiated chemistry in this mixture.

Moderate evidence.

Source: Fan et al. 2003, Environmental Science & Technology Link to this fact

Indoor air / Test-chamber measurement

A meaningful share of the formaldehyde (56-70%) and fine-particle mass (19-29%) generated when ozone reacts with fragrance terpenes comes from hydroxyl radicals that the ozone-terpene reaction itself produces as a byproduct, not from ozone reacting directly with the terpene or other chemicals.

Moderate evidence.

Source: Fan et al. 2003, Environmental Science & Technology Link to this fact

Indoor air / Measured in people or real products

Among 170 UK homes monitored for a year with passive VOC samplers, daily or near-daily use of air fresheners or of other household aerosols/sprays during pregnancy was statistically associated with the home's indoor total volatile organic compound (TVOC) concentration being in the top quartile measured across the study.

Moderate evidence.

Source: Farrow 2003, Archives of Environmental Health: An International Journal Link to this fact

Indoor air / Self-reported survey

In a small (n=69) follow-up of Atlanta-area adults with chemical hypersensitivity, the products most commonly reported to trigger symptoms were cleaning agents (88.4%), pesticides (81.2%) and perfume (81.2%), followed by tobacco smoke (82.6%) and car exhaust (72.5%).

Moderate evidence: Small, non-random follow-up sample (n=69, about 35% of the original 199 hypersensitive respondents); self-report of trigger identification, not exposure measurement.

Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact

Indoor air / Self-reported survey

The 11 household chemical products in this UK cohort's prenatal composite exposure score were used, in descending order of prevalence, as follows: disinfectant (87%), bleach (85%), aerosols (72%), air fresheners (68%), window cleaner (61%), carpet cleaner (36%), paint or varnish (33%), turpentine/white spirit (23%), pesticides/insect killers (21%), paint stripper (6%) and dry-cleaning fluid (5%).

Moderate evidence.

Source: Sherriff et al. 2005, Thorax Link to this fact

Indoor air / Measured in people or real products

Ordinary indoor ozone reacts with the natural oils on everyone's skin (mainly squalene) to produce a family of carbonyl and dicarbonyl air pollutants — with no fragrance, cleaning product, or air freshener needed. In a simulated two-person office at everyday occupied-room ozone levels (14-18 ppb), two of the compounds (6-MHO and 4-oxopentanal) reached 0.5-2.3 ppb.

Moderate evidence: Single research group; a small 28.5 m3 chamber with only 2 occupants, not a real home; concentrations scale with occupancy and ozone level.

Source: Wisthaler & Weschler 2010, Proceedings of the National Academy of Sciences Link to this fact

Indoor air / Measured in people or real products

A single person in a typical room is estimated to remove about 10-25% of the room's ozone just through skin-surface chemistry, before any ventilation, wall, or furnishing losses are counted.

Moderate evidence.

Source: Wisthaler & Weschler 2010, Proceedings of the National Academy of Sciences Link to this fact

Indoor air / Measured in people or real products

Using real-time air analysis (PTR-MS), researchers identified three dicarbonyl compounds and tentatively identified two hydroxy-ketone compounds from ozone reacting with skin oil that had never been reported before, none of which are picked up by the sampling methods routinely used to survey indoor air pollutants.

Moderate evidence: Single-lab chemical identification (bench-scale and simulated-office experiments); not yet independently replicated by another group.

Source: Wisthaler & Weschler 2010, Proceedings of the National Academy of Sciences Link to this fact

Indoor air / Measured in people or real products

In this study, carbonyl compounds coming off human skin were negligible when no ozone was present, and appeared within minutes once ozone was introduced — suggesting these carbonyls are produced by ozone reacting with skin oils rather than being emitted endogenously by the skin itself, as some earlier surveys of human skin volatiles had assumed.

Moderate evidence.

Source: Wisthaler & Weschler 2010, Proceedings of the National Academy of Sciences Link to this fact

Indoor air / Journalism

An independent indoor-air chemist (Charles Weschler) cautioned that the reported dryer-vent acetaldehyde concentrations are high enough to raise sensory-irritation concern if dryers are vented indoors, whether intentionally via indoor dryer-vent kits or unintentionally through equipment malfunction.

Moderate evidence: An expert's stated concern about a hypothetical indoor-venting scenario, not a measurement of indoor air; the underlying study measured only outdoor vent emissions.

Source: Kessler 2011 (EHP Forum), Environmental Health Perspectives Link to this fact

Indoor air / Review of other studies

Regulatory limits for airborne irritants like formaldehyde and ammonia are typically derived from a mouse reflex-breathing test (the Alarie/RD50 bioassay): the human occupational limit is estimated as about 3% of the mouse concentration that cuts breathing rate in half, a relationship checked across 89 chemical data pairs spanning six orders of magnitude.

Moderate evidence.

Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

Indoor air / Review of other studies

Approved nasal-spray and oral-inhalation pharmaceutical products deliver estimated benzalkonium chloride epithelial doses of roughly 0.1-5 micrograms per square centimeter (nasal) or under 1 nanogram per square centimeter (oral inhalation) — doses far below the concentrations used in most in vitro cytotoxicity and ciliotoxicity assays (typically 0.001-0.02% BKC, i.e., 1-200 micrograms/mL).

Moderate evidence.

Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact

Indoor air / Measured in people or real products

A flickering (flame-disturbed) candle can emit up to 1,700 times more soot than the same candle burning steadily and undisturbed, based on chamber measurements of one candle type under both conditions.

Moderate evidence.

Source: Andersen 2021, Indoor Air Link to this fact

Indoor air / Measured in people or real products

Candle wax and wick choice makes up to a 27-fold difference in soot, fine-particle, and particle-bound PAH emissions between candle types, but essentially no difference in NOx, formaldehyde, or gas-phase PAH emissions, in a controlled chamber study of five unscented pillar candles.

Moderate evidence.

Source: Andersen 2021, Indoor Air Link to this fact

Indoor air / Measured in people or real products

In unscented candles, formaldehyde and other carbonyl emissions stayed flat and low (39-54 micrograms per hour) regardless of wax type, wick type, or whether the flame was steady or flickering, which the study's authors attribute to the absence of added fragrance or dye, since those additives (not the wax or wick) are understood to be the main source of a candle's aldehyde emissions.

Moderate evidence.

Source: Andersen 2021, Indoor Air Link to this fact

Indoor air / Measured in people or real products

Burning a scented candle releases far more organic combustion by-products than burning an unscented candle of the same wax: total VOC emission rates reached up to 14,388 micrograms per candle per hour for scented candles versus 70-204 for the four unscented candles tested (24 fuel/fragrance combinations, chamber study).

Moderate evidence.

Source: Salthammer 2021, Environment International Industry-funded Link to this fact

Indoor air / Measured in people or real products

Benzo[a]pyrene, a combustion-linked carcinogen, was measurable in 5 of 24 candle-burning experiments (up to 12 nanograms per candle per hour) and only in scented candles; none of the 4 unscented candles produced a detectable amount.

Moderate evidence: Small n (5/24 detections); detection near the analytical limit of quantification, which the authors themselves note adds uncertainty to the calculated exposure comparisons.

Source: Salthammer 2021, Environment International Industry-funded Link to this fact

Indoor air / Measured in people or real products

The fragrance added to a candle, not the wax it is made from, is the main driver of extra combustion emissions: unscented candles made from four different waxes (palm, paraffin, soy, stearin) formed the lowest-emission cluster in the study's statistical analysis, while scented versions of the same waxes released far more VOCs, PAHs, and formaldehyde.

Moderate evidence.

Source: Salthammer 2021, Environment International Industry-funded Link to this fact

Indoor air / Other evidence

For rodent inhalation studies of irritating chemicals, extending a subchronic study to predict chronic effects needs roughly a 2-fold safety margin, and extending a shorter subacute study to chronic needs about 4-fold — both smaller than the values regulators previously used (2-fold and 6-fold).

Moderate evidence: Single reanalysis by one research team of one database; not independently replicated.

Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Other evidence

A rat inhalation study's no-effect concentration for eye/airway irritation predicts the human no-effect concentration reasonably well, but rats are on average about 3 times less sensitive than humans, so a safety factor of about 3 is needed when extrapolating from rats to people.

Moderate evidence: Small dataset (10-25 chemicals); many human studies only tested one concentration so the true no-effect level may be higher than reported.

Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Other evidence

German government toxicologists reviewing the data behind indoor air guide values concluded there is not enough evidence to lower the standard safety margin (10 to 20 times) currently used to protect sensitive groups such as people with chemical intolerance from irritating chemicals.

Moderate evidence: This is a decision to keep an existing regulatory default under uncertainty, not new evidence that the value of 10-20 is itself correct.

Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact

Indoor air / Measured in people or real products

In a sealed-room test, a reed diffuser's top three released chemicals were linalool acetate, linalool, and alpha-pinene, with linalool acetate alone making up 31-44% of everything measured.

Moderate evidence: Single product tested; sealed airtight chamber built to reach a maximum equilibrium, not a lived-in room.

Source: Zhang 2024, Cell Reports Physical Science Link to this fact

Indoor air / Measured in people or real products

Scented wax melts, even though they involve no flame or smoke, released enough fragrance terpenes to react with ordinary indoor ozone and trigger bursts of new nanoparticle formation in a full-scale test house, reaching concentrations above 1 million particles per cubic centimeter.

Moderate evidence: One test house, 3 scented wax melt products; a real-world field measurement, but a single research group's single building, not yet replicated elsewhere.

Source: Patra et al. 2025, Environmental Science & Technology Letters Link to this fact

Indoor air / Measured in people or real products

The estimated respiratory tract deposited dose of these new nanoparticles from scented wax melt use (median 2.9 x 10^10 particles per minute) was comparable to the dose rates reported for burning a scented candle, running a gas stove, or diesel and natural gas engine exhaust, and about 1,000 times higher than the same test house's background air.

Moderate evidence.

Source: Patra et al. 2025, Environmental Science & Technology Letters Link to this fact

Indoor air / Measured in people or real products

In a real-home field study of 32 occupied Hanoi houses monitored continuously for a week each (not a chamber), an incense-burning event raised PM2.5 in the burning room to a mean of 201.3 (SD 132.2) ug/m3, with a 1-minute peak of 825.5 ug/m3.

Moderate evidence.

Source: Tran 2021, Building and Environment Link to this fact

Indoor air / Measured in people or real products

After adjusting for outdoor PM2.5, season, cooking, cleaning, and smoking, incense-burning events were the largest contributor to indoor PM2.5 among all monitored indoor activities in 32 Hanoi homes, raising the geometric mean of total indoor PM2.5 by 120.3% (versus +71.6% for cooking, +52.2% for smoking, +40.5% for cleaning).

Moderate evidence: Single-city, single-cohort study with no independent replication; percentages are specific to this sample's burn frequency, ventilation, and background air quality.

Source: Tran 2021, Building and Environment Link to this fact

Indoor air / Measured in people or real products

Habitually burning incense frequently (4+ times/week) raised whole-week geometric-mean indoor PM2.5 by 61.6% versus non-use homes, after adjusting for outdoor air quality, season, house type, road proximity, and other indoor activities; occasional use (up to 3 times/week) raised it by 18.5%.

Moderate evidence: Habit groups were self-reported by occupants, not independently verified; effect size may not generalize outside this Hanoi sample.

Source: Tran 2021, Building and Environment Link to this fact

Indoor air / Measured in people or real products

Across all 32 Hanoi homes, the 24-h average indoor PM2.5 concentration (52.1 ug/m3) exceeded the WHO 24-h guideline in 97% of homes and Vietnam's own 50 ug/m3 ambient standard in 47% of homes, even before separating out incense burning.

Moderate evidence: Reflects Hanoi's generally poor ambient air quality as much as any single indoor source; outdoor PM2.5 (54.4 ug/m3) was itself higher than indoor.

Source: Tran 2021, Building and Environment Link to this fact

Indoor air / Measured in people or real products

In a lab chamber test, three of six candles — a strawberry candle, a clean-cotton candle, and a plain (unscented) reference candle — produced formaldehyde levels above both the ACGIH occupational guideline (325 ppb) and OSHA's legal limit (730 ppb) while lit, up to 2,098 ppb for the strawberry candle.

Moderate evidence.

Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact

Indoor air / Measured in people or real products

One kiwi-melon scented candle emitted more total measured VOC while sitting unlit (12,742 ppbC) than while it was actually burning (2,766 ppbC) — more than 4 times as much — and the unlit figure was comparable to a published emission rate for a carpet cleaner.

Moderate evidence.

Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact

Indoor air / Measured in people or real products

Using a mass-balance model of a realistic room scenario (one person present 8 h, two candles lit for 4 h, 20 cubic-meter room, 0.5 air changes per hour), Kim et al. 2016 calculate an 8-hour time-weighted-average formaldehyde concentration exceeding 100 ppb in the worst case, more than 6 times NIOSH's 16 ppb 8-hour recommended exposure limit.

Moderate evidence.

Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact

Indoor air / Measured in people or real products

Of every ingredient/route combination in this deodorant risk assessment, the tightest safety margin was for inhaling didecyldimethylammonium chloride (DDAC), a quaternary-ammonium biocide, from spray deodorants used at home or in cars: its calculated margin of exposure was 30, only about 1.2 times the regulatory target of 25, driven by an unusually low reference concentration for DDAC rather than by high measured exposure.

Moderate evidence.

Source: Kim et al. 2018, Science of The Total Environment Link to this fact

Indoor air / Animal study

In a mouse chamber study modeling occupational candle exposure, burning scented candles for 4.5 hours a day, 5 days a week, produced measured chamber levels of 2157.5 ng/m3 PAHs, 181 micrograms per cubic meter VOCs, and 219,000 nanoparticles per cubic centimeter (median size 10.7 nanometers) during active burning.

Moderate evidence.

Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact

Indoor air / Measured in people or real products

The plasma deodorant device itself generates ozone: about 1.5 ppm measured 3 cm from the outlet (roughly 7.5x the 15-minute occupational STEL of 0.20 ppm the authors cite), falling to about 0.16 ppm at 30 cm in a direct line and 0 ppm when the path to the sensor was blocked, which the authors say is below international occupational ozone limits at that distance.

Moderate evidence.

Source: Bok et al. 2024, Scientific Reports Link to this fact

Indoor air / Animal study

An "unscented" candle was not toxicologically inert: its headspace was 51.65% toluene by GC-MS peak area, and burning it in rats for 8 weeks still caused duration-dependent serum inflammation and lung injury compared with fresh air, though consistently less severe than the scented candle at every exposure duration tested.

Moderate evidence: One unscented candle product; wax/wick composition not disclosed; toluene here is an emission from the candle itself, not an added fragrance ingredient.

Source: Mohamed et al. 2025, Frontiers in Public Health Link to this fact

Indoor air / Other evidence

Burning a scented candle at low ventilation (0.5 air changes per hour) produced significantly higher total PAH and cancer-risk-weighted PAH emissions than at 1.0 or 2.0 air changes per hour, in a controlled chamber study.

Moderate evidence.

Source: Chen et al. 2026, Toxics Link to this fact

Indoor air / Other evidence

Relative humidity had a bell-shaped, non-monotonic effect on a scented candle's PAH emissions, peaking at 75% RH rather than at the lowest or highest humidity tested.

Moderate evidence.

Source: Chen et al. 2026, Toxics Link to this fact

Indoor air / Other evidence

Low-molecular-weight PAHs, dominated by naphthalene, made up roughly 87-92% of total PAH mass from scented candle combustion across all tested ventilation and humidity conditions, and were mostly in the gas phase rather than bound to particles.

Moderate evidence.

Source: Chen et al. 2026, Toxics Link to this fact

Indoor air / Measured in people or real products

Burning four unscented paraffin candles at once drove living-room NOx and HONO to 46.86 ppb and 1.63 ppb, about ten times higher than a single lavender-scented candle (0.02 ppb NOx, 0.23 ppb HONO) burned in the same room.

Moderate evidence.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

Once normalized per gram of wax burned, the scented candle's HONO emission rate (170.77 mg per kg of wax) was an order of magnitude higher than the unscented candles' (24.14 mg/kg) or incense sticks' (52.50 mg/kg), and higher than HONO from vehicle exhaust in a traffic tunnel (88-115 mg/kg fuel).

Moderate evidence: One scented candle product tested; emission index relies on a mass-balance model of room volume and air exchange, not direct stack sampling.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

Burning six sandalwood incense sticks in a living room produced isocyanic acid up to 0.38 ppb and methyl isocyanate up to 0.12 ppb, in a range the researchers compare to smoke measured downwind of large outdoor biomass fires.

Moderate evidence: One incense brand/type tested (n=3 replicate burns); methyl isocyanate stayed below the cited 0.5 ppb acute exposure limit.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

The isocyanic acid released by incense tracked its precursor hydrogen cyanide almost exactly as in open biomass burning (emission ratio 0.18, within the 0.16-0.50 range reported for wildland fires), showing incense combustion runs on the same pyrolysis chemistry as biomass burning.

Moderate evidence: One incense product; mechanism (HCN to HNCO conversion pathway) inferred from correlation, not independently confirmed.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

Incense smoke was far more chemically complex than candle smoke: over 100 distinct VOCs, including classic wood-smoke markers (acetonitrile, methoxyphenols) and a set of nitrogen-ring compounds (pyrroles) that were completely absent from either candle's emissions.

Moderate evidence: One incense brand vs. one scented and one unscented candle product.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

During morning stir-frying, oxygenated aldehydes (formaldehyde, acetaldehyde, acetone, butanal) surged to 19.38 ppb, 91% of the total measured aldehyde signal, and on a sunny day these aldehydes rebounded upward again shortly after the stove was turned off and the hood closed, tracking a sharp rise in sunlight-driven hydroxyl radical (OH) production rather than continuing to decline.

Moderate evidence.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

Frying with peanut oil (29.1% linoleic acid) produced more oxidized volatile byproducts than frying with olive oil (5.01% linoleic acid), consistent with peanut oil's greater share of double bonds available for hydroxyl-radical attack.

Moderate evidence: Single comparative cooking session per oil, not replicated; ingredients also differed between sessions.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Measured in people or real products

Ammonia, a byproduct rarely discussed for indoor combustion, rose 3-9 ppb above background during candle and incense burning (to 30-38 ppb total) and 4-10 ppb above background during cooking (to 30-44 ppb total), in both cases a statistically significant increase over pre-combustion levels.

Moderate evidence: Single-home measurements; cooking-related ammonia rise could not be cleanly separated from concurrent human-occupancy ammonia emissions.

Source: Deng 2026, Environment International Link to this fact

Indoor air / Other evidence

Burning scented candles releases VOCs, SVOCs, and particulate matter, including polycyclic aromatic hydrocarbons (benzo[a]pyrene, naphthalene, anthracene, pyrene) classified as carcinogenic.

Moderate evidence.

Source: Singh 2023, Environmental Science & Technology Link to this fact

Indoor air / Other evidence

In a small case series, removing mothballs and reducing scented cleaning/personal-care products, candles, and stored chemicals cut targeted indoor-air VOC categories by roughly a quarter to over 95% (e.g., naphthalene from mothballs down 96%, p-dichlorobenzene from moth crystals down 56-80%, odorants/fragrances down 26-80%) across three homes, measured by GC/MS air sampling before and after a structured home intervention.

Moderate evidence.

Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact

Indoor air / Measured in people or real products

In a 1989 NASA/ALCA interim study, sealed small chambers (0.69-0.87 m3) each holding one potted plant received a single one-time dose of benzene, trichloroethylene, or formaldehyde; over the next 24 hours, removal of that single chemical ranged from about 0% up to about 70%, depending on plant species and chemical.

Moderate evidence: Sealed chamber, zero air exchange, single pulse dose of one chemical, 24h, one plant per chamber; not a real room and the report does not claim it is.

Source: Wolverton 1989 Link to this fact

Indoor air / Measured in people or real products

General-population indoor air generally has higher styrene concentrations than outdoor air (residential surveys in the range of roughly 0.3-1.5 micrograms per cubic meter, vs. under 1 ppb / about 4.3 micrograms per cubic meter outdoors), with off-gassing from styrene-containing household products contributing to the indoor level.

Moderate evidence: Multiple national surveys (Canada, Finland, France, Germany, USA) show a fairly consistent range, but sources of indoor styrene were not quantitatively apportioned in most studies.

Source: IARC 2019 (Vol. 121) Link to this fact

Indoor air / Government agency

The US EPA states there is currently no evidence that a reasonable number of houseplants remove significant quantities of pollutants in homes and offices, even though houseplants have been shown to reduce levels of some chemicals in laboratory experiments.

Moderate evidence: A denial of the real-room extrapolation, not a measurement; EPA cites no specific study for either the lab result or the real-room gap.

Source: US EPA, "The Inside Story" (accessed 2026-09-28) Link to this fact

The industry / Self-reported survey

Even the companies selling products often don't know everything in them: all 20 'leader' consumer-product companies interviewed said ingredient or hazard information could be hard to get from suppliers, and 7 named suppliers' trade-secret claims as a major obstacle.

Moderate evidence: Interview study, 20 self-selected companies, 2009; no fragrance firms identified.

Source: Scruggs 2011, Environmental Science & Policy Link to this fact

The industry / Self-reported survey

Only 1 of 20 leading consumer-product companies could test its own products' chemistry in-house; most relied on suppliers' signed promises (18 of 20).

Moderate evidence: Counts are interview mentions.

Source: Scruggs 2011, Environmental Science & Policy Link to this fact

The industry / Lab study (cells or chemistry)

The fragrance industry's own data show its main explanation for how fragrance chemicals cause allergy doesn't cover most of them: 34 of 62 ingredients (55%) sensitize despite having no predicted protein-binding alert.

Moderate evidence.

Source: Lee 2024, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

The non-animal tests now used to set fragrance safety levels are typically off by about 2 to 3 times when predicting how potent an ingredient is.

Moderate evidence.

Source: Lee 2024, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

Those models underestimated allergy potency by more than fivefold for 18% of the 188 chemicals tested, and more than tenfold for 11%.

Moderate evidence.

Source: Natsch & Gerberick 2022, ALTEX Industry-funded Link to this fact

The industry / Animal study

Older synthetic musks (musk ambrette, AETT) caused nerve damage in animal studies and were later restricted.

Moderate evidence.

Source: Pinkas 2017, Environmental Research Link to this fact

The industry / Journalism

A perfumer writing in a chemistry journal said a natural ingredient such as rose oil is sometimes added in a "negligible quantity only to be able to say that you have rose oil in your formula", which "will please the marketing people" but does nothing for the scent.

Moderate evidence: Opinion; she advises against the practice and gives no frequency.

Source: Ellena 2008, Chemistry & Biodiversity Industry-funded Link to this fact

The industry / Animal study

Citronellol is treated as safe by default – GRAS at the US FDA, a 'non-toxic' biopesticide at the US EPA, and limited only by the fragrance industry's own voluntary IFRA standard – yet this government-funded study found it is brain-penetrant and calls for its content in consumer products to be regulated.

Moderate evidence: The call for regulation is the authors' conclusion from high-dose animal data; funded by the Korean Ministry of Environment, no industry money.

Source: Kim 2024, Journal of Hazardous Materials Link to this fact

The industry / Review of other studies

The industry's permitted levels for rose ketones (up to 0.07-0.8% depending on product type) overlap the concentrations at which already-sensitized volunteers reacted (0.05-0.1%), because the risk assessment is designed to prevent new allergies rather than to protect people who already have one.

Moderate evidence.

Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Review of other studies

The fragrance industry's safety assessment of 17 salicylates counted exposure from 10 personal-care product types only. Household cleaners and detergents, which the same report lists as uses, and breathing fragrance in were not included.

Moderate evidence.

Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Review of other studies

The industry panel judged each salicylate's safety one chemical at a time, although the same report says all 17 are broken down in the body to the same substance, salicylic acid.

Moderate evidence.

Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Measured in people or real products

In a French fragrance-and-flavor factory, the company's own measurements found the butter-flavor chemical diacetyl (linked to 'popcorn lung' in US factory workers) in workers' breathing air at 0.05–9 ppm during short tasks; 29 of 31 samples were above the 15-minute limit of 0.1 ppm recommended by the EU's scientific committee on occupational limits.

Moderate evidence.

Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact

The industry / Measured in people or real products

The standard EU (REACH) screening tool for estimating workers' chemical exposure predicted lower levels than were actually measured in 61% of 431 measurements in a fragrance-and-flavor factory, sometimes by more than 100-fold.

Moderate evidence: One plant; evidence base count from the paper's S4 table (paper: 37% of tool predictions were above the measurement); short task samples.

Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact

The industry / Self-reported survey

More than a third of Germans (37.8%) think people who wear perfume are more hygiene-conscious; fragrance can mask a smell but does not clean.

Moderate evidence: Attitude item; the 'does not clean' half is the author's argument, not a measurement.

Source: Klaschka 2020, Environmental Sciences Europe Link to this fact

The industry / Animal study

This lavender study was funded by a university with no declared industry involvement, unlike much of the evidence used to argue these oils are safe for children, which comes from the essential-oil trade or from a manufacturer of lavender's main constituents.

Moderate evidence.

Source: Kim & Lim 2022, Journal of Korean Medical Science Link to this fact

The industry / Animal study

The industry's guideline testing cleared the two lavender molecules that were NOT the most active ones: in the study it was answering, alpha-terpineol and terpinen-4-ol were the strongest on both the estrogen and androgen receptors, and BASF tested neither.

Moderate evidence: Comparison across two papers (Hareng 2024 vs Ramsey 2019) using different assay systems; the point is the untested molecules, not a disagreement about the tested ones.

Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

The hormone safety testing on lavender and tea tree oil constituents is incomplete: no regulatory steroidogenesis assay (OECD Test Guideline 456) has been published for any of the eight internationally defined constituents of either oil — including the two that an industry laboratory reported as clear on hormone receptors.

Moderate evidence: An absence-of-evidence claim about the published record as of 2026-09; states a testing gap, not a harm. Say 'not tested', never 'found unsafe'.

Source: Sharma 2024, Biomolecules Link to this fact

The industry / Review of other studies

Fragrance safety is self-regulated: IFRA, which represents about 90% of fragrance suppliers, issues voluntary guidelines, and much of the safety research it relies on is done by the industry's own institute (RIFM) and is unpublished.

Moderate evidence: Secondary figures; the unpublished-studies point is better sourced from RIFM dossiers themselves.

Source: BCPP 2018 Link to this fact

The industry / Industry source

The industry's standard safety package for a fragrance ingredient in 1994 covered acute poisoning and skin effects (irritation, allergy, sun reactions); breathing it in was not tested, because the industry judged inhalation 'not a route of toxicological concern'.

Moderate evidence.

Source: Ford 1994 (RIFM) Industry-funded Link to this fact

The industry / Review of other studies

EPA's reviewers warned that replacing one phthalate with a close relative (DINP for DEHP, DIBP for DBP) should not be assumed to be safer.

Moderate evidence: Based on weaker data for the substitutes (fewer studies, lower exposures), not on evidence they are equally harmful.

Source: Radke 2018 (US EPA), Environment International Link to this fact

The industry / Measured in people or real products

The essential-oil industry's published defense of lavender oil in a child's breast-growth case rested on showing the child's cologne was synthetic fragrance containing a phthalate: that clears lavender oil, not the cologne.

Moderate evidence: Describes the letter's argument; one case, no dose, no biomarker; does not show the phthalate or anything else caused the breast growth.

Source: Giroux & Orjubin 2020 (JCEM letter; Consortium Huiles Essentielles), The Journal of Clinical Endocrinology & Metabolism Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

A 2026 lab test that adds simulated human liver metabolism to a DNA-damage (Ames mutagenicity) test found MORE mutagenic activity in skin creams and lotions than the conventional animal (rat) version of the same test — the opposite of metabolism detoxifying the product. Standard safety testing, including industry fragrance-material dossiers, defaults to the rat version.

Moderate evidence.

Source: Schmidtmann 2026, Analytical Chemistry Link to this fact

The industry / Review of other studies

The cosmetics industry's own safety panel found that 5% benzyl alcohol and 2% benzoic acid provoke a non-allergic skin reaction (redness, swelling, itching) in most people tested with no prior sensitization needed, yet concluded both are "safe" up to 5% in cosmetics because it judged typical exposure limited, not because the reaction is rare.

Moderate evidence.

Source: Nair 2001 (CIR Expert Panel), International Journal of Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

The replacement tests are least accurate for the strongest allergens: they were wrong by about 6-fold for strong sensitizers and about 18-fold for the most extreme ones, almost always guessing them weaker than they are.

Moderate evidence: Geometric-mean fold error by LLNA potency class (Table 4); no human-outcome validation for this specific breakdown.

Source: Natsch 2015, Toxicological Sciences Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

When the same lab-dish tests that replace animal testing are checked against real human allergy-test panels instead of mouse data, they explain only about 32-45% of how strongly a chemical causes allergy in people, and the mouse test itself does barely better, explaining only 43%.

Moderate evidence: The strictly-human comparison dataset (n=62) is small and the author flags it as biased/non-representative; a larger human dataset might do better.

Source: Natsch 2023, ALTEX Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

Neither the animal test nor its lab-dish replacements are strong predictors of real human allergy thresholds; they are about equally weak, shown independently in 2015 and again in 2023.

Moderate evidence: Both comparisons reuse overlapping historical human patch-test literature (HRIPT/HMT), not independent new human data.

Source: Natsch 2023, ALTEX Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

Whether a chemical is irritating to cells in a dish, not just whether it reacts with proteins, drives a lot of the mouse allergy test's readout in ways that don't reflect real human allergy.

Moderate evidence: Statistical inference from regression coefficients across three chemical subsets, not a direct mechanistic experiment.

Source: Natsch 2023, ALTEX Industry-funded Link to this fact

The industry / Review of other studies

AETT was in fragrance use for 22 years before its neurotoxicity was documented, and cosmetic color additives are the only ingredient class the FDA actually regulates.

Moderate evidence: Regulatory-gap claim is accurate for the 1979 US framework described in the paper; verify current FDA cosmetic regulation status before using as a present-tense claim.

Source: Spencer 1979, Science Industry-funded Link to this fact

The industry / Animal study

The study's own authors, including two Research Institute for Fragrance Materials scientists, stated that the doses causing clear nerve damage in rats were 50 to 250 times their own estimate of maximum human fragrance exposure to musk ambrette, and that the lower-dose, longer-term study needed to assess real human risk was never done.

Moderate evidence: This is the study authors' own stated limitation, not an independent follow-up; no lifetime low-dose study has been conducted since (as far as this evidence base has found).

Source: Spencer 1984, Toxicology and Applied Pharmacology Industry-funded Link to this fact

The industry / Animal study

Musk ambrette is no longer used in fragrances; it was withdrawn from all skin-contact products in the 1980s, following both this neurotoxicity finding and separate reports of photoallergic skin reactions in real-world cologne use.

Moderate evidence.

Source: Spencer 1984; Ford 1994, Toxicology and Applied Pharmacology Industry-funded Link to this fact

The industry / Review of other studies

The fragrance industry's own most detailed exposure model to date estimates that about three-quarters of roughly 3,000 fragrance ingredients fall below a conservative safety threshold (TTC) for long-term systemic exposure, and 99% fall below it for inhalation — but by the same industry analysis, about a quarter of ingredients (777) are above their own systemic threshold and about half are above the skin-sensitization threshold (DST).

Moderate evidence.

Source: Lee 2024 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Review of other studies

As of 2024, the fragrance industry's aggregate exposure model finally covers household-care, air-care, and oral-care products and the inhalation route for its full ~3,000-ingredient inventory — a scope earlier industry safety dossiers from 1994, 2003, and 2007 explicitly left out or dismissed by a single-ingredient calculation.

Moderate evidence.

Source: Lee 2024 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Review of other studies

The industry's own model finds fragrance exposure from household-care and air-care products is far lower than from cosmetics and personal-care products, and almost entirely by inhalation rather than skin contact (household 95th percentile 0.2 ug/kg/day, air care 5 ug/kg/day, versus cosmetics/personal care about 50 ug/kg/day, nearly all dermal).

Moderate evidence: Based on a 350-ingredient sample modeled from industry-supplied concentration and use-frequency survey data, not measured breathing-zone concentrations.

Source: Lee 2024 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Government agency

FDA's own 2006 testing concluded there was insufficient data to find a human health hazard from phthalate esters in cosmetics and took no regulatory action, even though the phthalates were already known to be common and concentrated in fragrance and nail products.

Moderate evidence: This is the regulator's own stated position at the time (2006), not a new toxicity finding; FDA said it would continue to monitor and could revisit if new hazard data emerged.

Source: Hubinger & Havery 2006, Journal of Cosmetic Science Link to this fact

The industry / Industry source

The fragrance industry's aggregate consumer exposure model did not include any estimate of inhaled fragrance exposure until 2017, when it added an inhalation route for air fresheners, scented candles, and personal-care sprays only — 23 years after the industry's 1994 safety package dismissed inhalation testing.

Moderate evidence.

Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Industry source

Even after this 2017 update, the fragrance industry's own aggregate exposure model still explicitly excluded household cleaning and laundry products — the product category the industry's own 2003 safety-process paper says accounts for about 60% of fragrance volume — and named their inclusion as future work.

Moderate evidence.

Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Industry source

To build this exposure model, the fragrance industry combined three surveys that were never designed to work together — a 7-day product diary, a monthly recall survey, and a categorical daily-frequency questionnaire — by matching subjects only on age and gender and assuming they share the same habits for entirely unrelated products.

Moderate evidence.

Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Industry source

Some of the amount-per-use values feeding this industry exposure model come from very small studies — 10 Dutch adults for bar-soap-in-the-shower amounts, and a single non-distributional value for scented-candle amount per day — rather than large, representative samples.

Moderate evidence.

Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

The fragrance industry's own 2007 safety review of benzyl salicylate assessed allergy, toxicity, and cancer risk in detail but never tested it for hormone-like activity at all; the first test came two years later, from an independent lab with no fragrance-industry funding.

Moderate evidence.

Source: Charles & Darbre 2009, Journal of Applied Toxicology Link to this fact

The industry / Measured in people or real products

In RIFM's own comparison of 57 fragrance chemicals, the mouse test used to set fragrance skin-allergy safety limits agreed with real human sensitization thresholds within about 3-fold for 76% of the chemicals tested, but was off by up to nearly 800-fold for others, including hexyl and benzyl salicylate.

Moderate evidence.

Source: Api, Basketter & Lalko 2014, Cutaneous and Ocular Toxicology Industry-funded Link to this fact

The industry / Measured in people or real products

The older claim that PGME solvent vapor irritates the eyes and throat at 250 ppm comes from an unblinded 1970 study without objective eye measurements (20 of 23 subjects reported eye irritation at 250 ppm); a later double-blind study with objective eye tests found no effect at 100-150 ppm.

Moderate evidence.

Source: Emmen et al. 2003, Toxicology Letters Industry-funded Link to this fact

The industry / Government agency

California's 2022 law banning intentionally added PFAS in cosmetics (AB 2771), effective January 1, 2025, is expected by state toxicologists' own modeling to reduce PFAS reaching California wastewater treatment plants, particularly from shaving creams and gels, hair care products, and facial cleansers rather than from makeup.

Moderate evidence.

Source: Balan 2024, Environmental Science & Technology Link to this fact

The industry / Measured in people or real products

The study's own authors note that current diagnostic patch-test concentrations for oxidized linalool allergy are more than 500 times higher than the hydroperoxide levels they actually found in consumer products.

Moderate evidence: Industry-funded interpretation; does not itself prove patch tests over-diagnose, since already-sensitized skin can react to much lower doses than the diagnostic test threshold.

Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact

The industry / Other evidence

RIFM's founding scientific director personally authored the sole primary study behind the fragrance industry's 'quenching' safety exception; IFRA later codified it into a formal use-with-limonene rule (≥25% d-limonene) that required a higher proportion of the 'quenching' terpene than Opdyke's own 1976 test (~20% d-limonene) actually used.

Moderate evidence: The evidence base does not have IFRA's own documentation of why 25% (rather than the tested ~20%) was chosen, or of when/why the quenching exception was later withdrawn.

Source: Ford 1994 (RIFM), citing Opdyke 1976 Industry-funded Link to this fact

The industry / Measured in people or real products

Despite thousands of positive allergy-test reactions to oxidized limonene and linalool reported worldwide, the fragrance industry's own market-testing program concluded that where people are actually getting exposed to these allergens "remains elusive" — the industry itself has not identified the real-world consumer-product source of a widely documented skin allergy.

Moderate evidence.

Source: Natsch 2019, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Measured in people or real products

A musk fragrance chemical called ATTN (Versalide) disappeared entirely from human tissue in this 1996 study because industry had already stopped making it in 1980, after animal testing showed it damaged nerves – a real-world example of a musk being phased out after a toxicity finding.

Moderate evidence: Absence in 19 samples is consistent with, but does not by itself prove, the discontinued-production explanation the authors give; based on a small single-country sample.

Source: Rimkus & Wolf 1996, Chemosphere Link to this fact

The industry / Measured in people or real products

SC Johnson funded and co-authored a study that tested what was apparently its own newly developed fragranced air-sanitizer product in asthmatics and found no adverse ocular, nasal, or lung effects.

Moderate evidence.

Source: Opiekun 2003, Clinical and Experimental Allergy Industry-funded Link to this fact

The industry / Animal study

When RIFM's own scientists restrict the comparison to fragrance chemicals without known problematic chemistry, the mouse test used to set fragrance safety limits correlates strongly with real human sensitization thresholds (R-squared = 0.78 for 35 chemicals).

Moderate evidence.

Source: Roberts & Api 2018, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Measured in people or real products

This foundational human PGME irritation study has a direct Dow Chemical link stronger than later PGME papers in the wiki: one author was a Dow Chemical employee and the test material was Dow-supplied ('Dowtherm 209'), yet the study documents substantial irritation at concentrations relevant to Dow's own radiator-coolant product rather than minimizing it.

Moderate evidence: A single industry-linked study reporting an adverse finding is still one study; the funding link is recorded for transparency, not as proof the finding is unbiased in general.

Source: Stewart 1970 (Arch Environ Health), Archives of Environmental Health: An International Journal Industry-funded Link to this fact

The industry / Animal study

A commercial testing laboratory's mouse-bioassay claims of consumer-product toxicity (the same ASTM E-981/FOB method the lab later applied to air fresheners and colognes) failed an independent, blinded EPA/ManTech replication attempt when applied to carpets; the largest toxicity-looking signals traced instead to stress from the restrained-exposure test procedure itself, present even in air-only control animals.

Moderate evidence.

Source: Tepper et al. 1995, American Industrial Hygiene Association Journal Link to this fact

The industry / Review of other studies

Modern (post-1980s) European fabric conditioners almost all use esterquats, a cationic surfactant class engineered with a hydrolyzable ester linkage to biodegrade faster than the older DHTDMAC/DSDMAC softeners it replaced; the industry's own account frames the switch as environmental (biodegradability), not human-health, driven.

Moderate evidence.

Source: HERA Project 2008 (A.I.S.E./CEFIC) Industry-funded Link to this fact

The industry / Measured in people or real products

Tumble dryer manufacturers give directly conflicting instructions on cleaning the lint filter: some tell consumers to rinse it under water, others recommend a dishwasher, others dry methods only, and one (John Lewis) explicitly says never use water, for environmental reasons.

Moderate evidence: One UK market snapshot (24 brands, January 2023), not checked against other countries or against what consumers actually do.

Source: Cummins 2023, PLOS ONE Industry-funded Link to this fact

The industry / Other evidence

The clinical safety testing (HRIPT, CIT, or SIU) required to earn the NEA Seal is arranged and paid for by the manufacturer through a testing company of its own choosing; NEA states it "does not endorse or have a relationship with any clinical safety testing company" and instead reviews the submitted reports on paper through an independent physician panel.

Moderate evidence.

Source: NEA 2026 Link to this fact

The industry / Review of other studies

The US fragrance and cosmetics industry's principal safety-review and standard-setting bodies (IFRA, RIFM/REXPAN, the Personal Care Products Council, the Cosmetic Ingredient Review, the Voluntary Cosmetics Regulation Program) are industry-created and industry-funded, and their safety findings are not legally binding on member companies.

Moderate evidence.

Source: Reebs 2011 Link to this fact

The industry / Measured in people or real products

This 1977 dose-response safety study of a laundry-product preservative was conducted and authored in part by Procter & Gamble, the product's manufacturer, using an experimental in-house formulation; the co-author (Maibach) who supplied the sensitization-testing methodology also co-authored the wiki's other major P&G-funded laundry allergic-contact-dermatitis study 25 years later (Belsito et al. 2002).

Moderate evidence.

Source: Weaver & Maibach 1977, Contact Dermatitis Industry-funded Link to this fact

The industry / Other evidence

In a random sample of 100 high-production-volume industrial chemicals, 47 were also listed on EPA's Toxics Release Inventory (meaning they are emitted into air, land, or water in quantities over 10,000 pounds a year), and toxicity data were publicly available for less than half of those 47.

Moderate evidence: A single external audit, not independently replicated; concerns industrial chemicals broadly, not a named fragrance or consumer-product ingredient.

Source: Goldman 1998, Environmental Health Perspectives Link to this fact

The industry / Measured in people or real products

This study — the largest and most-cited test of whether laundry detergents cause allergic contact dermatitis — was funded by Procter & Gamble, which also supplied both detergents tested and had previously conducted its own unpublished non-irritancy testing of the same test concentrations with one of the study's authors.

Moderate evidence.

Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact

The industry / Animal study

Unilever toxicologists reviewed 92 public rat inhalation toxicology studies (from US EPA HPV/OECD SIDS reports and BfR, TNO, and ECETOC evaluations) and derived generic inhalation 'thresholds of toxicological concern' (TTCs), so that a consumer aerosol ingredient's measured exposure could be compared to a threshold instead of running a new ingredient-specific inhalation toxicology study.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Animal study

The paper's proposed inhalation systemic TTC ranges from 16.4 μg/kg/day for the least-toxic Cramer Class 1 chemicals down to 2.8 μg/kg/day for the more toxicity-presumptive Class 3 chemicals (roughly a 6-fold spread), while its separate local respiratory-tract TTC ranges from 2.1 to 0.73 μg/g lung tissue/day (about a 3-fold spread) — equivalent to 980/170 μg/day and 1400/470 μg/day respectively for a 60 kg adult.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Animal study

The dataset behind these inhalation TTCs excluded genotoxic carcinogens, in vivo mutagens, heavy metals, dioxins/PCBs, organophosphates, and polymers — chemical classes the authors say would already be disqualified from consumer aerosol use on other safety grounds — before applying a default uncertainty (safety) factor of 25 to the 5th-percentile NOAEC/NOAEL of the remaining 92 rat studies.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Animal study

Only 5 of the 92 chemicals in the database had local (respiratory-tract) NOAECs below the study's own 5th-percentile benchmark — sulfuric acid, trimellitic acid, glutaraldehyde, hydrogen peroxide, and 1,2-dichloro-4-nitrobenzene — and all were strong acids, bases, or reactive irritants that the authors say would already be excluded from consumer aerosol use on physicochemical grounds alone.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Animal study

The paper reports its inhalation-derived systemic TTCs (980 μg/day Class 1, 170 μg/day Class 3, for a 60 kg adult) sit within, and are not dramatically lower than, the oral-exposure-derived systemic TTCs for the same Cramer classes (1800 and 90 μg/day) — despite the inhalation calculation assuming 100% absorption versus the oral route's assumed 50% absorption factor.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Review of other studies

All three named authors of this inhalation-TTC methodology paper were Unilever employees at Unilever's own research center (Colworth Science Park, UK), and the paper states 'The authors declare that there are no conflicts of interest' even though the work was industry research explicitly aimed at reducing inhalation-toxicology testing requirements on the authors' own company's aerosol consumer products under REACH and the EU Cosmetics Directive's 2013 animal-testing ban.

Moderate evidence.

Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Journalism

The fragrance industry trade group RIFM (Research Institute for Fragrance Materials) publicly disputed the dryer-vent study, arguing it did not rule out the dryers, ambient air, or towels as VOC sources and lacked enough methodological detail for independent replication.

Moderate evidence.

Source: Kessler 2011 (EHP Forum), Environmental Health Perspectives Link to this fact

The industry / Industry source

The fragrance industry's aggregate consumer exposure model began in 2015 covering 19 personal-care and cosmetic product types across a 36,446-subject Europe/US survey, using dermal and oral exposure routes only — it did not estimate inhaled fragrance exposure at all.

Moderate evidence.

Source: Comiskey 2015 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Industry source

This industry exposure model's default assumptions are stated by its own authors to be conservative: 100% of a fragranced product applied to skin is assumed absorbed, and 100% of the contents of a spray product (body spray, eau de parfum, eau de toilette) is assumed to land on the skin, with none modeled as inhaled or lost to the air.

Moderate evidence.

Source: Comiskey 2015 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Other evidence

The fragrance industry's own probabilistic (Monte Carlo) exposure model estimated aggregate systemic exposure for four fragrance ingredients (vanillin, benzaldehyde, BMHCA, isoeugenol) at 11.5 to 25-fold lower than the deterministic worst-case method recommended by the EU's SCCS for assessing cosmetic ingredient safety.

Moderate evidence.

Source: Safford 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Other evidence

In this industry model, the highest simulated exposure to vanillin came from body lotion (prestige range, P95 8.79 mg/kg bw/day), eau de parfum (8.34) and eau de toilette (6.34), while plug-in air freshener and scented candles — despite having the highest simulated in-product concentrations of vanillin — produced comparatively low exposure (P95 1.81 and 0.81 mg/kg bw/day) because there is no direct skin contact and the modeled inhalation fraction is low.

Moderate evidence: Modeled, not measured; industry-funded (RIFM); pattern shown for vanillin, generalized by the authors to the other 7 ingredients tested.

Source: Safford 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Other evidence

The same industry exposure model's aggregate (whole-population) P95 exposure estimate can be lower than its own P95 exposure estimate among consumers of a single high-exposure product, because usage of any one product type is well under 100% of the population — e.g. body lotion use was modeled at about 17.3% of the population, and body spray, mouthwash, and hand cream use at only 1-2%.

Moderate evidence: Modeled usage proportions from industry-commissioned survey data (Kantar, SUPERB, BodyCare), not independently verified.

Source: Safford 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

The study comparing BAK against a preservative-free alternative (TBE) was co-authored by an employee of Lion Corporation, the company behind the TBE formulation, and declared no conflict of interest despite this employment relationship; no external funding was received.

Moderate evidence.

Source: Kabashima 2020, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact

The industry / Measured in people or real products

The same manufacturer developed and scaled up (to an 11-kilogram batch) a process that keeps PFOA below the 5 ppb detection limit: irradiating PTFE with gamma rays inside a sealed, oxygen-free polymer bag, then heat-treating it at about 150 degrees C, with the low PFOA level still holding after a year of storage.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

The industry / Measured in people or real products

The study authors point out that a batch of PTFE can be made to test 'PFOA-free' simply by heat-treating it in open air, but they state this only evaporates the PFOA into the surrounding atmosphere rather than destroying it, and call this approach a clear violation of the EU REACH regulation rather than a genuine fix.

Moderate evidence.

Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact

The industry / Review of other studies

When RIFM's own scientists switched from mainly human patch-test data (their 2017 categorization) to a full weight-of-evidence approach that also folds in animal, computer-model, and lab-dish data, the assigned allergy-potency category changed for 29% of the same 82 fragrance chemicals — moving to a weaker category for 20.5% of them and a stronger one for 8.5%.

Moderate evidence.

Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact

The industry / Measured in people or real products

Perfume that washes off fabric during rinsing does not just disappear into the drain: as surfactant concentration drops below the critical micelle concentration (measured at about 73.4 ppm in this study), micelles trapped in the wet fabric break open and redeposit their more hydrophobic perfume ingredients back onto the fabric, more strongly on cotton than on polyester because cotton retains far more water after spinning (about 0.7 kg water per kg dry cotton vs about 0.1 kg/kg for polyester).

Moderate evidence.

Source: Marcotullio 2025, Journal of Surfactants and Detergents Industry-funded Link to this fact

The industry / Measured in people or real products

The independent dermatologists who ran this study suggested deodorants should contain hydroxycitronellal at less than 0.032% to protect people already sensitized, well under the fragrance industry's own 1987 recommendation equating to about 1% in finished consumer products.

Moderate evidence.

Source: Svedman et al. 2003, Contact Dermatitis Link to this fact

The industry / Other evidence

The fragrance industry lowered its recommended limit for isoeugenol in consumer products from 0.2% to 0.02% in 1998, in response to documented high and rising rates of contact allergy to it.

Moderate evidence.

Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact

The industry / Measured in people or real products

The fragrance industry's own study found that grasping a scented candle for a total of 100 seconds transfers only about a quarter of a microgram per square centimeter of cinnamic aldehyde and eugenol to skin, which the authors say leaves a 1,000-fold or larger safety margin below the industry's own dermal sensitization threshold.

Moderate evidence.

Source: Api 2007 (RIFM), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Measured in people or real products

In the same candle, d-limonene transferred to hands in undetectable amounts in every subject and every round tested, while cinnamic aldehyde and eugenol transferred consistently — the study authors could not explain the difference and did not test whether the missing d-limonene had oxidized inside the candle into breakdown products that are known allergens.

Moderate evidence.

Source: Api 2007 (RIFM), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact

The industry / Other evidence

An industry-funded study measured that leave-on antiperspirants, skin lotions, and hair-styling products send well under 1% (often under 0.1% by 24 hours) of their D5 (cyclopentasiloxane) content down the drain, with the rest inferred to evaporate.

Moderate evidence.

Source: Montemayor 2013, Chemosphere Industry-funded Link to this fact

The industry / Other evidence

A rinse-off, in-shower hair conditioner discharged an estimated 40% of its applied D5 dose directly into wash water within 1-3 minutes of application, far more than any leave-on product tested.

Moderate evidence: The authors themselves call the 40% figure 'only an approximation' because the dosing control had just 4 replicates with high relative variance.

Source: Montemayor 2013, Chemosphere Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

Five parabens tested for comparison were, as a group, more estrogenic in this assay than any of the fragrance ingredients: benzylparaben was the single most potent substance in the whole study, exceeding estradiol's own maximal effect, yet the paper notes several fragrances with comparable estrogenic potency to parabens have not received similar regulatory attention.

Moderate evidence.

Source: Lange et al. 2014, Chemosphere Link to this fact

The industry / Review of other studies

The 2016 published critique that prompted Kim et al. to revise their scented-candle formaldehyde paper was authored by two National Candle Association staff members, not independent scientists.

Moderate evidence.

Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact

The industry / Review of other studies

After a separate 'exception letter' sent in March 2015 by the National Candle Association, the original study's authors deleted a sentence reporting that formaldehyde in three scented-candle types (925, 1022, and 2098 ppb) exceeded workplace TLV (325 ppb) and PEL (730 ppb) limits, and softened a paper highlight from 'exposure levels of some species are high enough to exceed guideline values' to 'can approach or exceed certain guideline values.'

Moderate evidence.

Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact

The industry / Review of other studies

Heinze and Silverman correctly identified that Kim et al.'s original formaldehyde concentrations, measured in a small 4.2-liter test chamber, cannot be directly scaled to real room volumes without correction.

Moderate evidence.

Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact

The industry / Animal study

Scented candles are marketed and used in hotels, restaurants, and spas for a calming, stress-relieving aromatherapy effect, but in a mouse model, scented candle fume exposure did not significantly reduce the stress hormone corticosterone that chronic social-disruption stress had raised.

Moderate evidence.

Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact

The industry / Review of other studies

Fragrance safety in the EU currently relies on industry self-regulation, managed by the International Fragrance Association (IFRA) and its research arm, the Research Institute for Fragrance Materials (RIFM); this report says it is unclear how much EU member states independently monitor compliance.

Moderate evidence.

Source: Tegengif 2022 Link to this fact

The industry / Measured in people or real products

A single fragrance molecule, beta-ionone, blocks the same nose receptors that detect the sulfur malodor methanethiol (a component of bad breath and sewer gas): when the malodor and beta-ionone were mixed and inhaled through one nostril, people rated the smell as weaker and less unpleasant, but when the same two odors were delivered to separate nostrils at the same time, that reduction disappeared, showing the masking happens at the receptor level rather than only in the brain's later processing.

Moderate evidence.

Source: Fukutani et al. 2023, Current Biology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

In lab dish tests, three human smell receptors that detect the sulfur gases methanethiol and hydrogen sulfide (OR2T1, OR2T6, OR2T11) only responded strongly when copper was added to the mix, and a copper-grabbing chemical shut the response back down, indicating these malodor receptors sense sulfur gases by using copper ions to grab onto them.

Moderate evidence.

Source: Fukutani et al. 2023, Current Biology Industry-funded Link to this fact

The industry / Measured in people or real products

Comparing this follow-up survey to FDA's original 2002-06 testing, 8 of 25 directly comparable cosmetic products no longer contained any phthalate ester, and nail products' any-phthalate detection rate fell from 6 of 6 to 11 of 24, evidence that some manufacturers reformulated to remove phthalate esters.

Moderate evidence: Category-level comparison across two separate market-basket surveys of not-identical product lots, not a matched before/after test of the same products.

Source: Hubinger 2010, Journal of Cosmetic Science Link to this fact

The industry / Measured in people or real products

FDA's own follow-up survey found dibutyl phthalate (DBP) persisting in nail products at concentrations essentially unchanged from its earlier 2006 survey (max 62,607 vs 59,815 ug/g), even as the share of DBP-positive nail products fell, complicating the assumption that phthalates were fully phased out of US nail polish by 2010.

Moderate evidence: Single FDA lab's own two surveys of different, non-identical product lots each time, not a matched-brand or matched-lot before/after test.

Source: Hubinger 2010, Journal of Cosmetic Science Link to this fact

The industry / Review of other studies

Global production of UV filters is estimated at about 10 million metric tons a year, of which 6,000-14,000 metric tons are released into coral reef zones annually; the global sunscreen market was valued at $10.3 billion in 2022 and is projected to reach $13.64 billion by 2026.

Moderate evidence: Production and market-value figures are industry/market-research estimates relayed by the review, not independently measured environmental releases.

Source: Hodge 2025, Marine Pollution Bulletin Link to this fact

The industry / Review of other studies

The study's authors estimate the societal cost of DEHP-attributable years of life lost at roughly $10.2 billion to $3.7 trillion depending on the economic valuation method used, and argue that plastic producers pursue production for profit without this cost being reflected in economic tradeoffs.

Moderate evidence.

Source: Hyman 2025, eBioMedicine Link to this fact

The industry / Government agency

In February 1992, the Business Council on Indoor Air (an indoor-air industry trade association) told HUD that the American Medical Association, American Association of Allergy and Immunology, American College of Physicians, and American College of Occupational and Environmental Medicine had all stated (December 1991) that there was "inadequate scientific evidence to establish the existence of MCS as a disorder," and asked HUD to correct guidance that recognized MCS as a handicap.

Moderate evidence.

Source: BCIA letter (1992) Link to this fact

The industry / Self-reported survey

The cosmetics industry generated its own dataset for how much lipstick, body lotion, and face cream people actually use, written by staff of the cosmetics trade association (CTFA), the fragrance industry's safety institute (RIFM), a contract statistics firm, and personal-care manufacturers including P&G, Unilever, Avon, Johnson & Johnson, Mary Kay, L'Oreal, Bath & Body Works and Takasago.

Moderate evidence.

Source: Loretz 2005, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Measured in people or real products

The fragrance industry's amount-per-use inputs for lipstick, body lotion, and face cream in its own aggregate exposure model come from a study where subjects used an unfamiliar substitute product for two weeks, not their own regular brand, and where the probability of daily use fell from about 99% on day 1 to 74-79% by day 14, fastest among the women who disliked the assigned product.

Moderate evidence.

Source: Loretz 2005, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Self-reported survey

The cosmetics and fragrance industry generated its own dataset for how much perfume, hairspray, foundation, shampoo, body wash, and antiperspirant people actually use, written by staff of the cosmetics trade association (CTFA), the fragrance industry's safety institute (RIFM), and personal-care manufacturers including P&G, Unilever, Avon, Johnson & Johnson, Mary Kay, L'Oreal, Dial, and Takasago.

Moderate evidence.

Source: Loretz 2006, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Self-reported survey

Real-time diaries found people using hairspray and other personal-care products up to six times more often than an older survey that just asked women to recall their past use, even though the two studies agreed fairly well on how much was used per application — suggesting recall surveys mainly undercount how often people use a product, not how much they use each time.

Moderate evidence.

Source: Loretz 2006, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Government agency

Twelve of the 28 public comments on the 2007 air-freshener petition came from air-freshener manufacturers and industry trade associations (including Reckitt Benckiser, SC Johnson, the Consumer Specialty Products Association, the American Chemistry Council's Phthalate Esters Panel, and the Fragrance Materials Association), all opposing every part of the petition and citing the fragrance industry's own self-regulatory bodies (RIFM, IFRA) as sufficient oversight.

Moderate evidence: Comment content as characterized by EPA, not independently verified against the original comment letters by this evidence base.

Source: EPA 2007 Link to this fact

The industry / Self-reported survey

The cosmetics industry generated its own dataset for how much facial cleanser, hair conditioner, and eye shadow people actually use, written by staff of the cosmetics trade association (CTFA), the fragrance industry's safety institute (RIFM), a contract statistics firm, and personal-care manufacturers including Procter & Gamble, Dial, Unilever, Johnson & Johnson, Mary Kay, L'Oreal, and Takasago, whose own conflict-of-interest statement says 'there are no conflicts of interest.'

Moderate evidence.

Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Measured in people or real products

US women in this study used far more hair conditioner (28.2 g/day at the 90th percentile) and somewhat more eye shadow (0.052 g/day) than the amounts the EU's cosmetics safety regulator (SCCS) uses in its own risk-assessment formula for those same product categories (3.92 g/day and 0.02 g/day) — a 7.2-fold and 2.6-fold gap, unlike lipstick, where the EU and US figures are essentially identical when compared at the same percentile.

Moderate evidence.

Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Other evidence

A QSAR model (SKINPERM) used to predict skin permeability over-predicted the actual measured penetration rate and permeability of propylene glycol and dipropylene glycol through human skin by roughly 2.6- to 5.1-fold in this 2011 study.

Moderate evidence.

Source: Fasano 2011, Toxicology in Vitro Industry-funded Link to this fact

The industry / Government agency

Benzophenone is widely used as a UV-curing photoinitiator for inks and varnishes, a fragrance fixative/enhancer and flavoring agent, a UV blocker in plastic packaging, and an additive in coatings, adhesives, laundry and household cleaning products; the US EPA classified it a high-production-volume chemical in 2003, with US annual production exceeding 1 million pounds (453,000 kg).

Moderate evidence: Production/use figures are the Working Group's synthesis of industry and HSDB/NTP secondary sources, not independently verified primary measurement.

Source: IARC 2013 Link to this fact

The industry / Other evidence

The industry surveys behind today's EU and US cosmetic safety limits (Hall 2007/2011 for Europe, Loretz 2005/2006/2008 for the US) measured how much product people use and how often, but the US survey never itself calculated a dose-per-bodyweight exposure figure — that conversion is done later, by the industry's own aggregate exposure models.

Moderate evidence: Describes only whether a dose-normalized figure was computed in the original survey, not whether the industry's later exposure models (Comiskey/Safford) did so correctly.

Source: Ficheux 2019, Table 3, Food and Chemical Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

Cosmetics Europe (the European cosmetics industry trade association) funded a standardized, OECD-compliant lab study measuring 24-hour skin penetration of 56 cosmetic-relevant chemicals, authored by scientists employed by L'Oreal, Unilever, Pierre Fabre, Procter & Gamble, BASF, Coty, and Beiersdorf, with the explicit goal of replacing a flat 50% default assumption about how much of an applied chemical passes through skin with chemical-specific measured data.

Moderate evidence.

Source: Hewitt 2020, Journal of Applied Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

For the 7 chemicals in this dataset with published human in vivo comparison data (hydrocortisone, testosterone, ibuprofen, benzoic acid, caffeine, DNCB, and nitrobenzene — none of them fragrance ingredients), measured skin penetration ranged from about 3% to 63% of the applied dose, a more than 20-fold spread that straddles the industry's flat 50% dermal-absorption default from well below to just above it.

Moderate evidence.

Source: Hewitt 2020, Journal of Applied Toxicology Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

In this standardized dataset, several volatile test chemicals lost most of their applied dose to evaporation from the skin surface rather than to skin absorption — naphthalene's mass balance was only 27% of the applied dose and 4-tolunitrile's only 20% — but the study measures only dermal delivery (skin plus receptor fluid) and never quantifies or discusses the airborne exposure that this evaporation implies for someone wearing a product containing these chemicals.

Moderate evidence.

Source: Hewitt 2020, Journal of Applied Toxicology Industry-funded Link to this fact

The industry / Government agency

The cosmetics industry's own safety panel (CIR, funded by the Personal Care Products Council) concluded in 2021 that Benzophenone-1, -2, -3, -4, -5, -6, -8, -9, -10, -11 and -12 are 'safe' in cosmetics at their present concentrations of use, including Benzophenone-3 (oxybenzone) used as a light stabilizer or fragrance-formulation ingredient at up to 0.5%.

Moderate evidence.

Source: CIR 2021 Benzophenones Industry-funded Link to this fact

The industry / Lab study (cells or chemistry)

A 2022 skin-absorption study of linalool, funded by the fragrance industry's own safety institute (RIFM) and run by RIFM's long-term contract lab, tested only fresh linalool and did not report the test material's oxidation state or test air-oxidized linalool, the form clinical studies link to skin allergy.

Moderate evidence: Industry-funded (RIFM); the gap mirrors the same undisclosed-oxidation-state pattern documented in RIFM's separate 2003 sensitization dossier for linalool.

Source: Brain et al. 2022 (An-eX/RIFM), International Journal of Pharmaceutics Industry-funded Link to this fact

The industry / Government agency

The COSMILE Europe cosmetic-ingredient app and database is run by Cosmetics Europe, described in its own press release as "the European trade association for the cosmetics and personal care industry," together with 12 national cosmetics-industry member associations, not by the European Commission or any EU government body.

Moderate evidence: This is the organization's own self-description of its ownership and funding, not an independent audit; the app itself was first built by a German industry association (IKW).

Source: Cosmetics Europe 2023 Industry-funded Link to this fact

Laws and loopholes / Measured in people or real products

More than 70% of the chemicals measured in childcare air had no health-based safety limit; several fragrance compounds were among 12 the authors flagged for further study.

Moderate evidence: Flags come from database/QSAR hazard scores, not measured effects.

Source: Hoang 2016, Indoor Air Link to this fact

Laws and loopholes / Review of other studies

No law in the US, the EU, or Australia requires air-freshener makers to list all their ingredients; a label can simply say 'fragrance'.

Moderate evidence: Review's legal summary (2016); EU cosmetics allergen labeling does not cover air fresheners.

Source: Steinemann 2017, Building and Environment Link to this fact

Laws and loopholes / Measured in people or real products

US product rules written to limit smog (ozone) exempt several chemicals that still form fine particles, and fragrance ingredients do not have to be disclosed.

Moderate evidence: Regulatory analysis in the paper.

Source: McDonald 2018, Science Link to this fact

Laws and loopholes / Review of other studies

The EU bans more than 1,400 substances from cosmetics, while US rules restrict only a handful.

Moderate evidence: EU list includes never-used substances; US rules changing under MoCRA 2022; verify against a regulatory source.

Source: Alblooshi 2025, Frontiers in Toxicology Link to this fact

Laws and loopholes / Journalism

In a 2010 undercover test by the US Government Accountability Office, the Energy Star program certified 15 fake products, including a gas-powered alarm clock the size of a generator.

Moderate evidence: Energy efficiency label, not chemical safety; EPA/DOE promised reform.

Source: Dahl 2010, Environmental Health Perspectives Link to this fact

Laws and loopholes / Measured in people or real products

Trace benzene was found in 83% of 79 US feminine hygiene products and 1,4-dioxane in 50%, yet these products are regulated as medical devices with no federal ingredient-disclosure requirement.

Moderate evidence: Trace ng/g levels; 1,4-dioxane is a surfactant by-product.

Source: Lin 2020, Environment International Link to this fact

Laws and loopholes / Review of other studies

History shows removing the exposure works: as industrial turpentine use fell from 94.5% of US supply as a solvent in 1935 to 4.5% in 1975, turpentine skin allergy declined with it.

Moderate evidence: Ecological historical correlation.

Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact

Laws and loopholes / Review of other studies

Official limits for the same gas odorant differed about 280-fold in 2009: Germany allowed 50 ppm at work, a Dutch health agency derived 0.18 ppm, and the US had no limit.

Moderate evidence: Regulatory values as reported by the paper (2009); may have been revised since.

Source: Baur & Bittner 2009, American Journal of Industrial Medicine Link to this fact

Laws and loopholes / Review of other studies

In the US, "fragrance-free" means that no ingredient is used solely to give a smell. A fragrance chemical that also does another job, such as benzyl alcohol used as a preservative, can legally be in a "fragrance-free" product.

Moderate evidence: US definition as quoted by dermatologists in 2007; not a legal analysis; FDA has no binding definition of "fragrance-free".

Source: Jacob & Barron 2007, Dermatitis Link to this fact

Laws and loopholes / Review of other studies

After German industry stopped using musk xylene in 1993, its level in breast milk fell about 70% in four years, but the related musk ketone, which was not phased out, did not fall.

Moderate evidence: Cites a BgVV 2000 press release; single-country natural experiment.

Source: Schmeiser 2001, International Journal of Hygiene and Environmental Health Link to this fact

Laws and loopholes / Self-reported survey

Nearly half (49%) of US families in a survey bought children's makeup from large online retailers, and US labeling law (the Fair Packaging and Labeling Act) requires ingredient lists on the package, not on the website.

Moderate evidence: Purchase share is survey self-report; legal point is the authors' reading of the FPLA as of 2022.

Source: Medley 2023 Link to this fact

Laws and loopholes / Review of other studies

The researchers report that citronellol content varies up to 1000-fold within the same product category, which they attribute to the absence of regulation of fragrance content in household products.

Moderate evidence: Stated in the discussion citing industry/market sources; no product measurements in this paper.

Source: Kim 2024, Journal of Hazardous Materials Link to this fact

Laws and loopholes / Measured in people or real products

Workers with fragrance-related asthma were twice as likely as other work-asthma cases to still be exposed at work (50% vs 26%) and more often had workers' compensation claims denied (30% vs 21%), though ER visit and hospitalization rates were the same.

Moderate evidence: Interviewed cases only (~58% of fragrance cases); unadjusted.

Source: Weinberg 2017, Journal of Asthma Link to this fact

Laws and loopholes / Review of other studies

More than 40% of US occupational exposure limits are set to prevent eye, nose, and throat irritation, and a systematic comparison of 18 agencies confirms that US, German, and EU regulators set substantially different limits for the same chemicals — overall stringency ranges from Poland's geometric-mean level of 0.23 to US OSHA's 0.61 (a 2.67-fold spread), with the EU's own 'health-based' indicative limits sitting above Germany's stricter national MAK limits.

Moderate evidence.

Source: Dalton & Jaén 2010, Current Opinion in Allergy and Clinical Immunology Industry-funded Link to this fact

Laws and loopholes / Review of other studies

A fragrance-and-flavor company reported that about half of the chemicals it handles are classified hazardous, and that few of the more than 3,000 flavoring substances in use have workplace exposure limits.

Moderate evidence: Industry self-description, no inventory published; flavor materials at one company.

Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact

Laws and loopholes / Review of other studies

US product labels only have to say "fragrance", not which chemicals, and household products need not list ingredients at all; MoCRA (2022) requires companies to name on cosmetic labels the fragrance allergens FDA designates by regulation (proposed rule was due June 2024), which the authors expect to be many, but not all.

Moderate evidence: Check current MoCRA rule status before quoting; household products are outside MoCRA; statute §609(b) is a mandate; check final rule status.

Source: Rodriguez 2024, Cutis Link to this fact

Laws and loopholes / Measured in people or real products

The UK national air-pollution inventory counts zero emissions of limonene or the silicone D5 from shampoos, shower gels, and skin products, although these were the two largest emissions measured from them.

Moderate evidence: The authors judge the missing mass small at national scale (~0.4 kt/yr vs 807 kt total UK VOC).

Source: Yeoman 2020, Indoor Air Link to this fact

Laws and loopholes / Review of other studies

Most national microbead bans cover only rinse-off products such as scrubs and cleansers; microplastics are still commonly used in leave-on products, especially color cosmetics like lipstick and eye makeup.

Moderate evidence: Narrative review; 8 of 14 listed jurisdictions explicitly rinse-off/exfoliant only; EU 2023/2055 is broader.

Source: Han & Kim 2025, Cosmetics Link to this fact

Laws and loopholes / Review of other studies

The EU bans or restricts more than 1,500 chemicals in personal care products and Canada about 800, while the US restricted 11.

Moderate evidence: Secondhand from a 2018 JAMA Intern Med commentary; EU count includes substances never used; US rules changed after MoCRA 2022.

Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact

Laws and loopholes / Lab study (cells or chemistry)

A finished perfume is usually not toxicity-tested as a whole; its safety is assessed on paper from its secret ingredient list. When researchers tested 42 whole perfumes directly, they found hazards that ingredient-by-ingredient assessment is not designed to catch.

Moderate evidence: EU framework described by the authors; the hazards are in vitro and unidentified.

Source: Morlock & Heil 2025, Journal of Chromatography A Link to this fact

Laws and loopholes / Review of other studies

An advocacy group that pushes for fragrance disclosure itself says many brand owners are not told by their fragrance suppliers what their fragrances contain, so a disclosure law has to reach the fragrance supplier.

Moderate evidence: Asserted without evidence; interview evidence is Scruggs & Ortolano 2011.

Source: BCPP 2018 Link to this fact

Laws and loopholes / Review of other studies

A 2015 CMAJ editorial (Flegel & Martin, CMAJ 187:1187, DOI 10.1503/cmaj.151097) states hospital environments free from artificial scents 'should become a uniform policy, promoting the safety of patients, staff and visitors alike'; the US CDC's own workplace policy separately says fragrance 'is not appropriate for a professional work environment' (CDC wording still unverified against a primary CDC source).

Moderate evidence.

Source: ASEQ-EHAQ 2020 (quoting CMAJ 2015 and CDC) Link to this fact

Laws and loopholes / Review of other studies

People with chemical sensitivities asked the US Justice Department to consider fragrance as an access barrier during its 2008 ADA rulemaking.

Moderate evidence: Shows the issue was raised in the record; the attachment makes no legal argument and our evidence base has no record of DOJ's response.

Source: DONTSPRAYCALIFORNIA 2008 (DOJ ADA docket) Link to this fact

Laws and loopholes / Advocacy group testing

In a 2010 Canadian survey, volunteers found no ingredient list on 28% of toothpastes and mouthwashes and 14% of antiperspirants and deodorants; in Canada, personal-care products sold as 'drugs' need list only their active ingredients.

Moderate evidence: Some missing lists were discarded outer packaging; 2010 Canadian law.

Source: David Suzuki Foundation 2010 Link to this fact

Laws and loopholes / Government agency

In the US, fragrance sensitivity or multiple chemical sensitivity can count as a disability under the Americans with Disabilities Act, but not automatically: it is decided case by case, usually on whether breathing is substantially limited.

Moderate evidence: Authors' reading of statute in a 2009 business-conference paper; no case survey; the 2008 ADA Amendments postdate their cases.

Source: De Vader & Barker 2009 Link to this fact

Laws and loopholes / Government agency

In Hunt v. St. Peter School (1997), a scent-free classroom was treated as a reasonable accommodation, but a school-wide fragrance ban was ruled an undue hardship.

Moderate evidence: One district-court case as described by the authors; the opinion itself is not in our evidence base.

Source: De Vader & Barker 2009 Link to this fact

Laws and loopholes / Review of other studies

As of 2011, US law let makers write 'fragrance' instead of listing its ingredients as a trade secret, and the FDA pre-approved only color additives in cosmetics; the industry's own review panel had declared just 9 ingredients unsafe since 1976.

Moderate evidence: US situation in 2011; MoCRA (2022) later added limited changes; CIR count from its 2011 website.

Source: Gilton 2011 Link to this fact

Laws and loopholes / Animal study

The EU cosmetics committee's own estimate of how much 4-MBC enters the body of someone using it (0.23 mg/kg body weight) was only three times below the no-effect dose, and thirty times below the lowest harmful dose, in this rat developmental study.

Moderate evidence.

Source: Schlumpf 2004, Toxicology Link to this fact

Laws and loopholes / Measured in people or real products

Glycol solvents brought into consumer products as 'low-reactivity' replacements, and largely exempt from VOC limits, still make a large share of consumer-product ozone because so much is used.

Moderate evidence: Model result (oxygenates ~37% of VCP ozone in NYC); exemption statement is the authors' summary of US rules.

Source: Coggon 2021 Link to this fact

Laws and loopholes / Review of other studies

US law has never defined "fragrance-free"; the only definition is of fragrance itself ("used solely to impart an odor", 21 CFR 700.3(d)), so an ingredient that smells but is also claimed as a preservative or moisturizer can go into a "fragrance-free" product. FDA's own website said in 1999 that "fragrance-free" products, like "unscented" ones, may contain fragrance chemicals.

Moderate evidence.

Source: Scheinman 1999, Journal of the American Academy of Dermatology Link to this fact

Laws and loopholes / Review of other studies

A 2015 CMAJ editorial by two physicians argued that hospitals should adopt uniform scent-free policies, because patients — unlike employees — cannot request accommodation and can be involuntarily exposed to fragrance from staff, other patients, or visitors.