Every fact on this site, with its evidence grade, its caveats, and a link to the source.
We start you on the strong ones: findings that have been replicated or come from one large, well-controlled study. Moderate and weak facts are here too, labeled for what they are. Use “Link to this fact” to share a single card.
Children and pregnancy / Measured in people or real products
About half of children's diaper-rash creams (13 of 28) and a third of children's sunscreens (10 of 29) listed fragrance.
Weak evidence.
Caveats
Small category counts; label count only. Sunscreen share is market-specific: 64.9% (87/134) of Danish children's sunscreens and sun sprays listed fragrance or a named allergen (Botvid 2023), so 'a third of sunscreens' should not be generalized beyond Brazil; diaper creams were not reported separately in Denmark.
Source: Uber 2024, Jornal de Pediatria (Rio de Janeiro) Link to this fact
Children and pregnancy / Measured in people or real products
In 130 Danish and Finnish mothers, phthalate breakdown products were reported in essentially every breast milk sample (95-100% for each of the six measured) — but an independent, more contamination-controlled US study (Hines 2009) found the analogous class of monoester phthalate metabolites in under 10% of milk samples from a separate cohort, and declined to report its own milk hydrolytic-monoester data (which would include MEP) as likely contamination-inflated.
Weak evidence.
Caveats
1997-2001 samples; composite home-collected milk; phosphoric acid was not added at collection 'due to logistics' (this page's own Methods/limitations), a known contamination risk for hydrolytic monoesters. Hines 2009 (EPA/CDC, tighter contamination controls) found the analogous metabolite class in <10% of milk samples and withheld its own milk hydrolytic-monoester data on contamination grounds. US EPA systematic review (Radke 2018) separately excluded this study's milk data as a critically deficient exposure matrix.
Source: Main 2006, Environmental Health Perspectives Link to this fact
Children and pregnancy / Measured in people or real products
Baby boys whose mothers' milk contained more dibutyl phthalate had slightly lower free testosterone at 3 months (about 15% lower per 10-fold rise). For diethyl phthalate, the fragrance phthalate, the link was with higher SHBG, and its free-testosterone trend was not significant. These are correlations in 96 boys, not proof of harm.
Weak evidence.
Caveats
MBP–free T r = −0.22 (p = 0.033); mEP–free T r = −0.19 (p = 0.07, NS). US EPA review excluded this study (breast milk critically deficient as an exposure matrix for short-chain phthalates) and rated infant-testosterone evidence indeterminate (Lin 2011: MEP r = −0.10). 46% of Danish mothers used breast pumps.
Source: Main 2006, Environmental Health Perspectives Link to this fact
Children and pregnancy / Measured in people or real products
In one early, small US study, boys in the highest phthalate group had about 4 to 10 times the odds (3.8-10.2) of a shorter-than-expected anogenital distance than the lowest group, depending on the phthalate. A larger (N=753) follow-up by the same group found much smaller effect sizes for the one phthalate class (DEHP) that replicated, and did not test comparable categorical odds ratios.
Weak evidence.
Caveats
Single small cohort with very wide CIs (MEP OR 3.8, 1.03-13.9); US EPA rated this cohort's AGD data (extended n=106) low confidence. The DEP (MEP) part did not replicate in three larger cohorts, including the same group's own N=753 TIDES follow-up (Swan 2015), which also found smaller continuous effect sizes for the metabolites that did replicate (DEHP: beta -1.12 to -1.43 in TIDES vs -3.50 to -5.13 in this cohort, per Swan 2015's Discussion), consistent with lower current-day exposure. Quote as one small study's result only; prefer the EPA review or Swan 2015 for general claims.
Source: Swan 2005, Environmental Health Perspectives Link to this fact
Children and pregnancy / Self-reported survey
In a US survey, parents reported that 7 in 10 children aged 12 and under (219 of 312) had used makeup or body products such as face paint, glitter, nail polish, or body spray, including more than half of children aged 3 or younger (48 of 84).
Weak evidence.
Caveats
207 self-selected parents recruited mostly online in NYC/Boston/Houston; not nationally representative; ~60% of raw responses excluded as spam/fraud. Partial external check: in a Brazilian clinic survey (Melo 2020) per-category color-cosmetic rates matched Medley's (lipstick 18.8% vs lip ≈21%, nail 22.4% vs ≈22%), but the 70% total is driven by body products (face paint, glitter, bath bombs) that Melo did not ask about, and Melo found make-up in only ≈3% of infants, so the under-3 figure reflects body products, not make-up.
Source: Medley 2023 Link to this fact
Children and pregnancy / Self-reported survey
Among US children who used makeup or body products, about 1 in 8 used them daily, about 1 in 5 wore them for 8 hours or more, and about 1 in 3 had swallowed some in the past year.
Weak evidence: Parent report for 217 child users; ingestion differed sharply by ethnicity (41% vs 11%), possibly a question-wording effect.
Source: Medley 2023 Link to this fact
Children and pregnancy / Self-reported survey
Most US children who use makeup also use products made for adults: only about a third (36%) used mostly children's products.
Weak evidence.
Caveats
Parent estimate of product share; small non-representative sample. Applies to makeup only: for cleansers, a Brazilian clinic survey (Melo 2020) found the majority used children's products (children's soap 56.5%, children's shampoo 65.9%; adult soap 37.3%, adult shampoo 27.2%, rising with age), so do not write 'most children use adult products' generally.
Source: Medley 2023 Link to this fact
Children and pregnancy / Self-reported survey
In a US survey, boys and girls who used makeup or body products used fragrance products (perfume, cologne, body spray) at the same rate, about 31%.
Weak evidence.
Caveats
Scent-purpose products only; cleansers excluded, so not a fragrance-exposure prevalence. Indirect support for sex parity: in Melo 2020 (Brazil, 182/276 perfume users, 126 girls) at least 56/150 boys (≥37%) used perfume, so perfume is not a girls-only product; but the Brazilian level (66% of all children) is 3x the US level (≈21%), so the ~31% figure must not be generalized.
Source: Medley 2023 Link to this fact
Children and pregnancy / Self-reported survey
The only population study of lavender and tea tree oils and hormone problems in children (556 US children) was too small to rule out a risk: regularly exposed children had 2.8 times the rate of endocrine diagnoses, with a 95% confidence interval from 0.35 to 22 times.
Weak evidence: Not statistically significant; parent-reported diagnoses; self-selected natural-product users; 9 events. Supports 'not ruled out', not 'causes'.
Source: Hawkins 2021, International Journal of Pediatrics and Adolescent Medicine Industry-funded Link to this fact
Children and pregnancy / Measured in people or real products
In 2007, US government (NIEHS) scientists described three boys aged 4–10 who developed breast tissue while using products containing lavender oil or lavender and tea tree oil (a homemade balm, hair gel and shampoo, soap and lotions); in each case it went away within months of stopping the products.
Weak evidence: 3 case reports, dechallenge only, no rechallenge, products not analyzed; causation contested (BASF guideline tests negative for linalool/linalyl acetate; Braunstein 2023 review).
Source: Henley 2007, New England Journal of Medicine Link to this fact
Children and pregnancy / Review of other studies
In the reported cases, children had been using lavender-scented products regularly (violet-water colognes, shampoos, soaps, baby bath, lotions) or sat beside a classroom diffuser, and breast growth went away after the products were stopped; early breast growth in children often goes away on its own, so this does not prove cause.
Weak evidence.
Caveats
Case reports with dechallenge only; no comparison group; at least one of the violet-water colognes declared and contained no essential oil by an industry analysis (Giroux & Orjubin 2020). Linklater 2015's own transient alpha-fetoprotein/prolactin elevation resolved on its own over the same 12 months, for an unrelated physiological reason (infant liver immaturity) the authors themselves cite — a concrete illustration, from inside this same case, that concurrent findings can normalize without being caused by the product change.
Source: Hawkins 2020, Complementary Therapies in Medicine Industry-funded Link to this fact
Children and pregnancy / Measured in people or real products
Four prepubertal children (three girls with early breast development and one boy with breast growth) whose doctors recorded continuous use of products they identified as containing lavender saw the breast tissue disappear within three to six months of stopping the product.
Weak evidence.
Caveats
Four uncontrolled case reports, dechallenge only, no product analysis by the authors, and no chemical measured in any child; both conditions can resolve spontaneously. An essential-oil industry analysis later reported the boy's violet-water cologne declared and contained no essential oil (DEP, alpha-isomethyl ionone, and azo dyes instead), and one girl's baby bath only 'very low' lavender oil (unquantified).
Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact
Children and pregnancy / Self-reported survey
At one Miami children's hospital, 16 of the 24 children seen over seven years for unexplained early breast growth had been using lavender-scented products; 14 of the 16 were Hispanic and the products were violet-water colognes of a kind often applied to babies.
Weak evidence.
Caveats
Clinic case tally with no unexposed comparison group and no use-prevalence denominator; a clinic aware of the lavender hypothesis will ask about lavender; one violet-water cologne from this clinic's case reports declared and contained no essential oil by an industry analysis. Diaz 2016 (2015, same hospital, corresponding author Alejandro Diaz also a co-author here) reported 3 boys with the same outcome in the years just before this tally's window; those 3 cases are almost certainly a subset of this 16/24 figure, not additional to it, so this figure and Diaz 2016 should never be added together.
Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact
Children and pregnancy / Measured in people or real products
One of the four children had never used a lavender product at all: she sat beside a classroom lavender oil diffuser that ran all day for a year, and her breast tissue regressed three months after the diffuser exposure stopped.
Weak evidence: Single case report, no air measurement was made in the classroom, and measured indoor terpene levels elsewhere are far below the concentrations that were active in the cell assays.
Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact
Children and pregnancy / Measured in people or real products
In the same 2018 NGO test, a children's shampoo had 24 unlabeled chemicals flagged for health hazards (17 on the fragrance-industry list), and a baby shampoo had 6.
Weak evidence: Counts, not amounts; single samples; not peer reviewed; not a risk ranking.
Source: BCPP 2018 Link to this fact
Children and pregnancy / Measured in people or real products
In a Danish–Finnish study (hormones measured in 96 of 130 baby boys), some phthalates in mothers' breast milk went with hormone changes at 3 months that point to weaker male-hormone action (higher SHBG; lower free testosterone for dibutyl phthalate only).
Weak evidence.
Caveats
Association; hormones in 96 boys; mEP (DEP) free-T link not significant (p = 0.07); 46% of Danish mothers used breast pumps; US EPA review excluded this study (milk critically deficient as exposure matrix) and rated infant testosterone indeterminate. Cite the primary, not the thesis, which inverted the direction.
Source: Main 2006 Link to this fact
Children and pregnancy / Self-reported survey
Children's lipstick, nail polish, and eyeshadow use was about the same in a Brazilian hospital survey and a US parent survey (roughly 19-22%, 22% and 11-13%), but perfume use was three times higher in Brazil (66% vs about 21%).
Weak evidence.
Caveats
Our cross-study arithmetic (Medley per-user rates re-based to all 312 children); different definitions ('perfume' vs 'fragrance products primarily for children'), ages (<=14 vs <=12) and sampling.
Source: Melo 2020, Revista Paulista de Pediatria Link to this fact
Children and pregnancy / Self-reported survey
Every one of 13 Washington DC childcare facilities that reported health data had at least one child with physician-diagnosed asthma, with a typical (median) facility rate of about 10%.
Weak evidence: Center-Director-reported, not chart-confirmed; no exposure-outcome link tested; n=13.
Source: Quirós-Alcalá 2016, Environmental Research Link to this fact
Children and pregnancy / Measured in people or real products
Three more boys (ages 9-11) developed breast tissue while using lavender-labeled products, a shampoo or an 'agua de violetas' cologne sprayed on by a parent since early childhood; in each case it resolved within about 4 months of stopping the product.
Weak evidence.
Caveats
Three uncontrolled case reports, dechallenge only, no rechallenge; same hospital and a shared corresponding author (Alejandro Diaz) as Ramsey 2019's later clinic tally, so this is not an independent replication of the case count.
Source: Diaz 2016, Journal of Pediatric Endocrinology and Metabolism Link to this fact
Children and pregnancy / Measured in people or real products
A 14-month-old girl in Melbourne, Australia developed breast tissue while being given five different lavender-scented infant products every day (wipes, shampoo, body wash, cream, and lotion); it went away after the products were stopped, and this case has no connection to the better-known United States case series.
Weak evidence.
Caveats
One case report (letter to the editor), dechallenge only, no rechallenge, no product testing; the exposure was identified only after the family saw a documentary about this exact link, not through routine clinical questioning.
Source: Linklater & Hewitt 2015, Journal of Paediatrics and Child Health Link to this fact
Children and pregnancy / Review of other studies
Continuous nebulized albuterol (CNA), prepared from a benzalkonium-chloride-containing multidose 0.5% albuterol dropper bottle at standard pediatric dosing (10-20 mg/hour), would deliver an estimated 800-1600 micrograms of benzalkonium chloride over 4 hours — several-fold above the approximately 300-microgram cumulative dose shown to cause bronchospasm in adults with mild asthma.
Weak evidence.
Caveats
This is an arithmetic extrapolation from adult mild-asthma dosing studies to pediatric severe-asthma continuous nebulization, not a measured pediatric dose or outcome; no controlled trial has tested continuous nebulized albuterol with vs. without BAC in children.
Source: Prabhakaran 2017 Link to this fact
Children and pregnancy / Other evidence
In a retrospective cohort of 1,298 children with acute asthma treated with continuous nebulized albuterol (15 mg/hour) at Children's Hospital of Philadelphia, using a benzalkonium-chloride-containing dropper-bottle formulation, 31% required prolonged therapy (more than 24 hours) or had clinical deterioration.
Weak evidence.
Caveats
This retrospective cohort (Kenyon et al. 2014) had no benzalkonium-chloride-free comparison group, so the association with BAC is not established; the review's own authors call the causal link speculative ("tempting to speculate").
Source: Prabhakaran 2017 Link to this fact
Children and pregnancy / Self-reported survey
Household ammonia use was the only one of 10 individual cleaning agents (out of 30 agent-outcome comparisons) significantly associated with an outcome in this study: adolescents in homes where ammonia was ever used had lower odds of rhinitis, adjusted OR 0.60 (95% CI 0.44, 0.82), than those in homes that never used it.
Weak evidence.
Caveats
The study's own authors call this a likely chance finding given the number of associations tested and their limited statistical power to explore it further; not a basis for claiming ammonia protects against rhinitis.
Source: Bukalasa et al. 2019, Environment International Link to this fact
Children and pregnancy / Other evidence
Lilial's metabolites have been measured, at very low concentrations, in the urine of children and adolescents in Germany (geometric mean about 10.2 µg/L for p-tert-butylbenzoic acid, about 1.5 µg/L for lysmeral, and below quantification limits for lysmerylic acid and hydroxy-lysmerylic acid).
Weak evidence.
Caveats
This is a citation, within Jablonská 2023, of a separate human-biomonitoring survey (Murawski 2020, GerES V), not primary data generated by this paper; our evidence base does not yet hold that source directly.
Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact
Children and pregnancy / Review of other studies
US dermatology guidance recommends including aluminum in baseline allergy patch testing for children, given a high prevalence of aluminum allergy in children and early-life exposure to aluminum through childhood vaccines.
Weak evidence: A single-sentence guidance recommendation in a narrative review, not new pediatric data; the review does not report a pediatric aluminum-allergy prevalence figure itself.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Children and pregnancy / Government agency
In animal studies, a pregnant female's exposure to an endocrine-disrupting chemical can affect not only her offspring but her offspring's offspring, because developmental exposure can alter reproductive-cell programming that carries across generations.
Weak evidence: Evidence for these transgenerational effects comes from animal studies cited in the report; no multigenerational human dataset is cited for this specific claim.
Source: WHO/UNEP 2012 Link to this fact
Children and pregnancy / Other evidence
Prenatal exposure to phthalates in synthetic candle fragrance can promote permanent, irreversible changes to fetal immune-system development and contribute to childhood asthma and allergies.
Weak evidence: Secondhand citation of a general phthalate-immune mechanism paper, not a candle-specific exposure or outcome measurement; no dose given for candle-derived phthalate exposure.
Source: Singh 2023, Environmental Science & Technology Link to this fact
Children and pregnancy / Measured in people or real products
In a case-control study of adolescents aged 12-18 (62 with PCOS, 33 controls), urinary BPA levels were positively correlated with polycystic ovarian morphology seen on ultrasound.
Weak evidence: Single small study (Akgül 2019, cited within this review), not replicated in adolescents elsewhere in the review.
Children and pregnancy / Review of other studies
Studies of pregnant women's phthalate exposure and their children's later weight disagree in direction: one study linked higher maternal DEHP and DINP metabolites to a greater chance of excess infant weight gain, while another found children born to mothers with the highest DEHP exposure actually had slightly lower body fat at birth than those with the lowest exposure.
Weak evidence.
Caveats
Results vary by specific phthalate compound, child sex, and study design; the direction of effect (more fat vs. less fat) is inconsistent across the available prospective cohorts, so no reliable direction of effect can be claimed for maternal phthalate exposure and infant body composition.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
Children and pregnancy / Other evidence
In a small human study, petrolatum and paraffin oil applied to the forearms of 9 adults and 7 infants penetrated only into the stratum corneum (the skin's outer dead-cell layer) in both age groups, with petrolatum reaching deeper into that layer (up to about 30 micrometers) than paraffin oil (under 10 micrometers), but neither substance was detected passing into living skin layers or the bloodstream.
Weak evidence.
Caveats
Single small study (16 subjects total, both age groups pooled in the review's reporting) using a lab technique (confocal Raman spectroscopy) not independently replicated for infant skin in this review; industry-funded secondary source relaying the primary study, not independently re-analyzed here.
Source: Stamatas et al. 2008, via Petry et al. 2017, Toxicology Letters Industry-funded Link to this fact
Fragrance is everywhere / Review of other studies
A 2022 review of 37 studies found that phthalates, parabens, aldehydes, and aluminum salts are the contaminants most often reported in perfumes, colognes, and related scented products.
Weak evidence: Non-quantitative review with factual slips; cite primary studies for numbers.
Source: Kazemi 2022, Journal of Environmental Health Science and Engineering Link to this fact
Fragrance is everywhere / Measured in people or real products
Pine-scent chemicals were also common in Korean household products: alpha-pinene from 19% and beta-myrcene from 12%.
Weak evidence: Headspace presence only; high detection threshold.
Source: Kwon 2007, Journal of Hazardous Materials Link to this fact
Fragrance is everywhere / Hypothesis
Immigrant women in the US most often work as house cleaners and make up 71% of manicurists; an expert job-exposure tool rates both jobs as probably exposed to fragrance chemicals, and house cleaning also to cleaning-product ingredients such as alkylphenols and antimicrobials.
Weak evidence: Exposure ratings from job descriptions (WORC), not measurements.
Source: Knox 2026, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Fragrance is everywhere / Measured in people or real products
The same perfume does not come off the skin the same way every day: in women not on the pill, a fixed dose of vanilla on the forearm was rated about 3 times stronger on cycle day 22 than during menstruation.
Weak evidence: 18 women (9 per group), 25 male raters, no hormone confirmation, no unperfumed control, no statistics printed, storage time unreported.
Source: Chróst 2021, Journal of Cosmetic Dermatology Link to this fact
Fragrance is everywhere / Measured in people or real products
In a mannequin-head test of 16 UK day face moisturizers, the authors report that one application (0.45 g) delivered on average about 16 times more limonene-type terpenes than 24 hours of typical UK home air, and, for the 7 products whose ethanol reached the nose, about 340 times more ethanol.
Weak evidence.
Caveats
Primary: Yeoman 2022 (Indoor Air 32:e12948), Table 6. The abstract's 'up to' is wrong: ×16 and ×339 are means over products with a nonzero dose (14/16, 7/16); maxima ×37 and ×804; over all 16 the medians are ×9 and ×0. Absolute doses are small (≤1.2 mg limonene; below UK PHE limits). The paper's own breathing-zone traces (Fig. 2, limonene ≤0.16 mg/m³) imply doses ~15–500× lower than its tables (evidence base arithmetic), so the ratios are unverified. No people; unheated head, lab at 5 ACH; 'limonene' = all monoterpenes.
Source: Yeoman 2022 via Rádis-Baptista 2023, Journal of Xenobiotics Link to this fact
Fragrance is everywhere / Review of other studies
An NGO analysis (Plastic Soup Foundation, 2022) reported that 87% of products from major European cosmetic brands contained microplastic ingredients.
Weak evidence: NGO figure, unreferenced in the review, definition not stated; major European brands only.
Fragrance is everywhere / Measured in people or real products
In the same 33 breastfeeding women, urinary MEP (the metabolite of DEP, the fragrance phthalate) was on average about 57 times higher in women who "often" used nail polish than in women who never did (2,874 vs. 50.5 micrograms per liter).
Weak evidence.
Caveats
Small pilot study (n=33); frequency-group sizes not reported; perfume/cologne use was not asked about, so fragrance products cannot be separated from nail polish as a source; the difference was significant only on untransformed means, and the authors themselves suggest nail-polish users may also use more perfume and other DEP-containing products.
Source: Hines 2009, Environmental Health Perspectives Link to this fact
Fragrance is everywhere / Self-reported survey
Among Atlanta-area adults who reported chemical hypersensitivity, symptom onset was reported before age 20 in about a third of cases (32.4%), suggesting hypersensitivity is not exclusively an adult-onset condition.
Weak evidence.
Caveats
Retrospective self-report of childhood/adolescent onset in adults; no pediatric clinical verification; age-of-onset table has an internal mismatch with the running text for the older age brackets (see the page's Notes).
Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact
Fragrance is everywhere / Journalism
An EHP news report on a small Seattle-area study found that scented laundry detergent and dryer sheets sent volatile organic compounds, including several classified by EPA as hazardous air pollutants, out through home dryer vents into outdoor air.
Weak evidence: Secondary news coverage of one small two-home study with no replicates; numbers cross-checked and match the primary study (Steinemann 2013) exactly.
Source: Kessler 2011 (EHP Forum), Environmental Health Perspectives Link to this fact
Fragrance is everywhere / Review of other studies
Deodorants alone are estimated to deliver roughly 1,000 metric tons of fragrance per year to the German population, based on standard daily-dose, dermal-retention, and perfume-content assumptions.
Weak evidence: A calculated estimate from published dose and market-size figures, not a measured total; depends on assumed 1% dermal retention and 3-5% perfume content.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
Fragrance is everywhere / Measured in people or real products
In this study, fibers from ordinary household laundry outnumbered the deliberately added test-blanket fibers in outdoor snow samples at both homes — suggesting day-to-day laundry drying sheds more microfiber than a single garment alone.
Weak evidence.
Caveats
These 'other' fibers were identified only by visual shape and color under a microscope, not confirmed as textile fiber or identified chemically (no FTIR/Raman); their true source was not verified.
Source: Kapp & Miller 2020, PLOS ONE Industry-funded Link to this fact
Fragrance is everywhere / Review of other studies
Airborne nano- and microplastic concentrations measured in prior studies range from about 50 nanograms per cubic meter to 47 micrograms per cubic meter depending on location, illustrating how variable ambient exposure can be, though this paper does not connect that airborne range quantitatively to the topical doses it actually tested on skin.
Weak evidence.
Caveats
This figure is cited by Song et al. 2024 from earlier atmospheric-measurement studies (their refs 39-42), not measured by this paper itself, and the paper does not attempt to translate an airborne concentration into an equivalent skin dose.
Source: Song et al. 2024, Journal of Hazardous Materials Link to this fact
Green, natural and unscented / Measured in people or real products
Scented tampons carried a median of 692 ng/g of fragrance terpenes against 2.9 ng/g in unscented ones.
Weak evidence: Only 2 scented vs 20 unscented tampons (p=0.04).
Source: Lin 2020, Environment International Link to this fact
Green, natural and unscented / Government agency
Under EU/UK law, a 'free from [substance]' cosmetic claim about a substance already banned for all EU cosmetics would appear to fall under the rule barring claims that dress up mere legal compliance as a special product benefit.
Weak evidence.
Caveats
This is our own reading of the regulation's general Criterion 1(3) applied to 'free from' wording, not a quotation naming that claim type, and no enforcement decision confirming this application was found.
Source: Commission Regulation (EU) No 655/2013 Link to this fact
Green, natural and unscented / Self-reported survey
'Fragrance-free'/'unscented' deodorant claims are not a reliable guarantee for fragrance-allergic people: in a cited patient survey, 4.7% of fragrance-contact-allergic patients who had used an unscented deodorant in the past 3 months got a rash from it.
Weak evidence: Figure is relayed from Lysdal and Johansen 2009, not Klaschka's own data; not in our evidence base as a primary yet.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
Green, natural and unscented / Lab study (cells or chemistry)
A cold-atmospheric-plasma prototype device killed over 90% of two underarm-odor bacteria (Staphylococcus hominis 99.81%, Corynebacterium xerosis 90.99%) after 3 minutes of exposure in lab culture, and cut total electronic-nose sensor response to two major axillary-odor chemicals by about 51% (HMHA) and 34% (3M3SH) after 5 minutes, without applying antimicrobial chemicals or fragrance to skin.
Weak evidence.
Caveats
Antibacterial test used agar-cultured bacteria; deodorizing test used excised porcine skin dosed with pure synthetic odor compounds in methanol, not human sweat. Single lab, single prototype, no independent replication, no human skin testing.
Source: Bok et al. 2024, Scientific Reports Link to this fact
Green, natural and unscented / Other evidence
Candles made from renewable waxes (beeswax, soy, coconut, palm) scented with natural essential oils are generally safer and more sustainable than paraffin candles, but still carry an environmental cost through deforestation and habitat destruction from increased crop demand.
Weak evidence.
Caveats
No emissions or land-use quantification given; our own chamber data (Salthammer 2021, Andersen 2021) also show wax type has little effect on formaldehyde/PAH output compared to fragrance load, so a wax switch alone may not reduce indoor-air health risk even if it changes the environmental footprint.
Source: Singh 2023, Environmental Science & Technology Link to this fact
Green, natural and unscented / Other evidence
Study participants were given a free 'starter kit' of unscented cleaning products and 'alternative cleaning recipes' as part of a personalized action plan to reduce indoor VOC exposure, and researchers observed reduced use of scented products at follow-up visits.
Weak evidence.
Caveats
Product-use reduction was assessed by researcher observation during a scheduled visit, not by continuous monitoring, and patients knew they were being evaluated (compliance may be overstated).
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Health effects / Review of other studies
A 2022 review concluded that links between contaminants in perfumes and cancer, breathing problems, and hormone disruption are 'probable' but still need research to prove.
Weak evidence: Evidence mostly from phthalate/paraben studies not perfume exposure.
Source: Kazemi 2022, Journal of Environmental Health Science and Engineering Link to this fact
Health effects / Lab study (cells or chemistry)
In lab tests on cancer-derived nerve cell lines, three unnamed commercial fragrances changed cell shape and structure after 72 hours and cut the share of cells carrying oxytocin and vasopressin receptors in some lines but not others.
Weak evidence: Cell lines only; fragrances unidentified; no replication; only one cell line per sex.
Source: Sealey 2015, Environmental Research Link to this fact
Health effects / Hypothesis
Silent Spring Institute researchers name house cleaners and nurses as priority jobs for cutting exposure to fragrance, cleaning, and personal-care chemicals linked to breast cancer in lab and animal studies.
Weak evidence: No exposure or cancer data in these workers.
Source: Knox 2026, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Health effects / Review of other studies
Many everyday chemicals, including some released by scented and cleaning products, act on the same irritant-sensor nerves in the nose and airways (TRPA1 and TRPV1), one reason very different products can cause similar symptoms.
Weak evidence: Mechanism largely from lab/animal studies; dose relevance to homes untested.
Source: Molot 2023, Neuroscience and Biobehavioral Reviews Link to this fact
Health effects / Animal study
In animal and lab studies, common scent chemicals such as linalool, limonene, and eugenol act on brain signaling systems; what lifelong low-level exposure does in healthy people has never been studied.
Weak evidence: Mostly high-dose animal/in-vitro pharmacology; often protective effects in disease models.
Source: Pinkas 2017, Environmental Research Link to this fact
Health effects / Lab study (cells or chemistry)
In lab studies, inflammation lowers the threshold for this irritant receptor, a proposed reason scent reactions can be worse when airways are already inflamed.
Weak evidence: Mechanistic pathway only; not demonstrated in people exposed to products.
Source: Mihara & Shibamoto 2015, Allergy, Asthma & Clinical Immunology Link to this fact
Health effects / Measured in people or real products
Two German gas-works plumbers who repeatedly hand-poured the gas odorant tetrahydrothiophene in an unventilated room developed chronic rhinitis and lasting airway obstruction; neither had allergies on skin testing, and the accident insurer accepted both as occupational disease.
Weak evidence: Two case reports; exposure estimated, not measured; one worker smoked ~16 pack-years; industrial odorant, not fragrance.
Source: Baur & Bittner 2009, American Journal of Industrial Medicine Link to this fact
Health effects / Lab study (cells or chemistry)
Musk ketone does not damage DNA by itself, but in rat liver enzymes and human liver cells it made known carcinogens like benzo[a]pyrene more mutagenic.
Weak evidence: One laboratory's data (the review's senior author); human-cell LOEL 50 ng/ml is 12-70x above whole-milk levels.
Source: Schmeiser 2001, International Journal of Hygiene and Environmental Health Link to this fact
Health effects / Animal study
In two of the five products the airflow reduction kept worsening after the exposure ended.
Weak evidence.
Caveats
Mice, n=3-12 per time course; no human counterpart; mechanism unknown. An independent replication attempt (Tepper et al. 1995, carpets, full text now in our evidence base) found no significant carpet-related toxicity overall via individual-animal statistics, but it never measured airflow limitation or post-exposure persistence of any respiratory endpoint, so it does not directly test this finding either way.
Source: Anderson & Anderson 1998, Archives of Environmental Health Link to this fact
Health effects / Review of other studies
Frequent private use of household disinfectants (a composite of methods including hand-wash, machine, sponge, and spray disinfection) was linked to close to a threefold increase in the odds of newly developing asthma in a single cross-sectional wave of young German adults (Weinmann 2017, OR 2.79, 95% CI 1.14-6.83); the evidence for household sprays alone driving that same result was already weak in that wave (OR 2.79, 95% CI 0.84-9.20), and a 10-year longitudinal follow-up of the same cohort (Pacheco Da Silva 2025) found no significant association between persistent spray-only use and current asthma or wheeze (point estimates at or below 1.0 for every outcome), with only a non-significant, attenuated OR of 1.68 (95% CI 0.48-5.88) for sustained use of multiple disinfectants/cleaning products together.
Weak evidence.
Caveats
Two analyses of the same German SOLAR cohort (Weinmann 2017's cross-sectional SOLAR II wave, and Pacheco Da Silva 2025's 10-year longitudinal follow-up adding SOLAR III with latent-class exposure profiles) now agree that spray-specific use is not significantly associated with adult asthma. The only positive signal across both papers is a composite 'persistent use of multiple DCPs' profile, which itself weakened from a significant OR 2.79 (single wave, simple frequency composite) to a non-significant OR 1.68 (10-year follow-up, latent-class model, wide CI 0.48-5.88). Both papers are single-cohort, self-reported-exposure studies from the same research group, so per the grading rule this stays below moderate. The follow-up nulls are underpowered (1,143 of the original 2,051; only ~8-12% in each persistent-use profile; CIs span roughly 0.5-6), so they weaken the claim without refuting it. Other cohorts not yet in our evidence base reported positive spray-asthma associations (ECRHS, Zock 2007; French EGEA, Pacheco Da Silva 2023); don't cite this cohort as evidence that sprays are safe.
Source: Salonen 2024, Environment International Link to this fact
Health effects / Review of other studies
Doctors have published detailed reports of 12 young children (8 boys, 4 girls) whose breasts began to grow while they used lavender or tea tree oil products such as colognes, baby bath soap, or hair gel; in every case the growth went away within months of stopping.
Weak evidence: Case reports only; no rechallenge; this kind of breast growth often regresses on its own; the review itself concludes causation is not shown.
Source: Braunstein & Braunstein 2023, touchREVIEWS in Endocrinology Industry-funded Link to this fact
Health effects / Lab study (cells or chemistry)
In human adrenal cells, eight common fragrance terpenes — eucalyptol, geraniol, carvone, 3-carene, ocimene, both pinenes, and dihydro-beta-ionone — cut production of the androgen precursor DHEA by 13–31%, and six others cut the activity of aromatase, the enzyme that makes estrogen, by 22–33%.
Weak evidence.
Caveats
Single 10 µM concentration, ~140–200× above what indoor air or ordinary product use could produce internally; the mass-spectrometry check was non-significant for eucalyptol (p = 0.0574) and null for dihydro-beta-ionone; the same 10 µM killed up to 50% of a prostate-cancer cell line by 48 h. Always state the concentration.
Health effects / Lab study (cells or chemistry)
In a lab-grown 3D model of human skin, polystyrene fragments up to 10 µm were cytotoxic and inflammatory in keratinocytes, but only the fragments 2 µm or smaller penetrated into the dermis (average maximum 4.7 µg) within an hour, switching on inflammation genes there.
Weak evidence.
Caveats
One 3D skin model study (Song 2024); independently read the same way by a second review (Menichetti et al. 2025, J Xenobiot), which also reports the <2 µm penetrating cutoff and notes that in ex vivo human and mouse skin from the same primary study, the cutoff for any penetration was stricter still, under 1 µm. Not intact living human skin; no real-use dose.
Health effects / Lab study (cells or chemistry)
Many perfumes contain strongly antibacterial compounds: activity against Gram-negative bacteria appeared at 50 billionths of a liter, and a single spray is about 2,000 times that amount.
Weak evidence: Plate assay with a marine bacterium; effect on the skin microbiome inferred by the authors, not tested.
Source: Morlock & Heil 2025, Journal of Chromatography A Link to this fact
Health effects / Measured in people or real products
In the same test, patients rated breathlessness and cough higher after perfume at the eyes (1.5 vs 0.4 and 0.9 vs 0.3 on a 0-3 scale), yet lung function, oxygen saturation, and breathing rate did not change at all.
Weak evidence: Single-blind (scorers apparently not blinded), 3 of many symptoms analyzed, n=11; the airway symptoms did not replicate double-blind (Elberling 2006: 6/11 perfume vs 5/11 placebo).
Health effects / Lab study (cells or chemistry)
A small 2026 follow-up study found mutagenic and cell-killing compounds in 8 perfumes, consistent with an earlier 42-perfume finding from the same German lab.
Weak evidence.
Caveats
Same lab and platform as the earlier study, not independent; only 8 unnamed perfumes, unclear overlap with the 42; simulated liver metabolism was built for this paper but explicitly not tested on the perfumes; no antibacterial or hormone-related endpoints were run.
Source: Schmidtmann 2026, Analytical Chemistry Link to this fact
Health effects / Measured in people or real products
A small clinic study found that a real cologne challenge produced an objective, reproducible 18-58% drop in FEV1 (lung function) within minutes in asthma patients who already reported cologne sensitivity, blocked mostly by bronchodilators rather than cromolyn or blocking the sense of smell.
Weak evidence: N=4 evaluable patients, unblinded first exposure, cologne dose never measured, single cologne brand, all pre-selected for a cologne-sensitivity history, 1986, unreplicated.
Source: Shim & Williams 1986, The American Journal of Medicine Link to this fact
Health effects / Measured in people or real products
Pleasant fragrance smells can measurably calm the body (raising a marker of parasympathetic "rest and digest" activity by up to 47% for pine scent and 26% for citrus), but once that same citrus scent has reacted with ozone, the calming effect reverses into a small drop in that same marker.
Weak evidence.
Caveats
Each condition (pure pine, pure citrus, and the ozone-reacted citrus mixture) comes from a separate, small study, not one head-to-head design; the review's own authors suggest perceived unpleasantness of the reacted mixture, not necessarily toxicity, may explain the reversal.
Source: Wolkoff & Nielsen 2017, Environment International Link to this fact
Health effects / Self-reported survey
In a 10-year longitudinal follow-up of a German young-adult cohort (SOLAR, n=1,143), only participants who persistently used multiple disinfectants and cleaning products (sprays, disinfectant sprays, and nonspray disinfection methods) weekly at two assessments 10 years apart showed an elevated point estimate for current asthma (OR 1.68) and current wheeze (OR 1.71) compared with no weekly use; neither reached statistical significance (95% CI 0.48-5.88 and 0.75-3.90).
Weak evidence.
Caveats
Same underlying cohort as Weinmann 2017 (SOLAR 2 exposure data reused); small persistent-use subgroup (8.2% of n=1,143); wide confidence intervals; incident-asthma/wheeze estimates too imprecise for inference; authors draw no causal conclusion.
Health effects / Animal study
When the air freshener's emissions were combined with fresh latex-paint emissions, the mixture was not less toxic in mice than paint alone — the behavioral (FOB) score rose further and significantly, countering claims that air fresheners neutralize or mask other indoor pollutants.
Weak evidence: Single product, single co-pollutant, one dose combination, mouse behavioral scoring only; not tested with other pollutant classes or in humans.
Source: Anderson & Anderson 1997, Archives of Environmental Health Link to this fact
Health effects / Other evidence
California state scientists estimate that cosmetics may account for at least 4% (and plausibly much more, given wide uncertainty) of the PFOA-related chemicals measured in San Francisco Bay Area wastewater.
Weak evidence.
Caveats
The comparison spans a very wide range (roughly 4% to several hundred percent of the median measured loading) because of unreliable use-concentration inputs; this is an environmental-loading estimate, not a personal health-exposure estimate.
Source: Balan 2024, Environmental Science & Technology Link to this fact
Health effects / Animal study
In ex vivo real human and mouse skin (not a lab-grown skin model), plastic nanoparticles only penetrated when they were smaller than about 1 micrometer, and human skin let slightly more through than mouse skin at that size, likely because human hair follicles are larger.
Weak evidence: Single primary study (Song et al. 2024) as read by this review; ex vivo excised tissue, not living skin measured during real use; no real-use cosmetic dose.
Source: Menichetti et al. 2025, Journal of Xenobiotics Link to this fact
Health effects / Measured in people or real products
Almost half (44%) of patients in the founding irritable larynx syndrome series related their symptom onset to a viral illness, most often not a simple upper respiratory infection but herpes zoster, Epstein-Barr virus, viral meningitis, Lyme disease, or post-viral chronic fatigue syndrome.
Weak evidence.
Caveats
Retrospective patient-recalled association, not confirmed causally; n=39, one clinic; the paper's own abstract says "one third", which its own Results text ("almost half") and Table 4 (17/39=43.6%) contradict.
Health effects / Review of other studies
Citronella oil, marketed as a natural insect repellent, has been banned in the European Union and Canada since 2006, partly because it contains methyl eugenol, which the US National Toxicology Program considers 'reasonably anticipated to be a human carcinogen' based on animal studies.
Weak evidence.
Caveats
No human carcinogenicity data exist for methyl eugenol; this is a regulatory ban and an animal-based NTP classification relayed by a secondary review, not measured harm from using citronella products.
Source: Ramsey 2020 (YJBM), Yale Journal of Biology and Medicine Link to this fact
Health effects / Review of other studies
No published study has been found that tests whether quaternary ammonium compounds specifically from laundry fabric softeners or dryer sheets, as opposed to disinfectant or cosmetic-preservative exposure, cause asthma or skin sensitization in consumers.
Weak evidence: This is an evidence-gap statement, not a positive finding; the review also never discusses esterquats, the ester-linked chemistry that dominates modern fabric softeners, at all.
Source: Peyneau 2022, Frontiers in Toxicology Link to this fact
Health effects / Review of other studies
Estimated prevalence of multiple chemical sensitivity across the reviewed epidemiological literature ranges from about 1% to more than 15% of the population, a spread the review attributes to diagnostic difficulty, lack of standardized case-definition criteria, and differing recognition of the condition across countries.
Weak evidence.
Caveats
Secondhand synthesis of several distinct primary studies with different case definitions and populations, not a single standardized measurement; the review does not report the underlying studies' individual case definitions in enough detail to weight the range.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Review of other studies
A cohort of laborers acutely exposed to gasoline vapors above allowed limits during an underground tunnel-excavation job later developed symptoms similar to those reported in multiple chemical sensitivity, and the study authors argued the workers' sociocultural profile made simple psychosomatic suggestibility an unlikely sole explanation.
Weak evidence.
Caveats
Cited secondhand from Davidoff et al. (primary study not yet in our evidence base); occupational cohort with no independent control for pre-existing chemical sensitivity, and "unlikely to be suggestible" is the original authors' qualitative judgment, not a tested exclusion of a psychological contribution.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Review of other studies
Some solvents can theoretically sensitize the heart muscle to the body's own adrenaline-type hormones, raising a theoretical risk of arrhythmia or cardiac arrest under chemical exposure in people with multiple chemical sensitivity.
Weak evidence.
Caveats
Cited from a toxicology reference textbook (Olson, Acute Intoxications, Poisons, Pharmaceutical Substances and Drugs), not from any MCS-specific study; the review's own authors state this risk "has not been detected in any epidemiological study so far." Mechanistic/theoretical only.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Self-reported survey
In the same MCS patient sample, an anxiety-depressive symptom cluster (anxiety, palpitations, depression, sleep disturbance, chest tightness) was statistically distinct from, and less prevalent than, the hyperosmia/asthenia and respiratory clusters, leading the authors to call for more study of the psychosomatic aspects of MCS.
Weak evidence: Cross-sectional, no control group; cannot show whether anxiety-depressive symptoms are a cause, a consequence, or a comorbidity of MCS; see contradictions register C45.
Source: Del Casale 2020 Link to this fact
Health effects / Review of other studies
A review of MCS mechanism studies describes hyperosmia (heightened smell sensitivity from a lowered odor-detection threshold) as common in multiple chemical sensitivity, and cites a small brain-imaging study where MCS patients showed stronger brain responses than healthy controls specifically at odor-recognition-threshold and normal-perceived odor levels.
Weak evidence.
Caveats
Secondhand summary of a single small study (Azuma et al. 2016, 12 patients/7 controls) not independently read or verified in this evidence base; runs counter to other reviews' claim that MCS patients have normal odor thresholds.
Source: Palmieri et al. 2020, Reviews on Environmental Health Link to this fact
Health effects / Review of other studies
Small studies cited in this review report MCS patients have lower catalase and glutathione S-transferase (GST) enzyme activity than healthy controls, potentially impairing detoxification of chemical substances.
Weak evidence: Secondhand from a single research group's studies (De Luca et al.), not independently verified; enzyme-activity differences do not establish that they cause MCS symptoms.
Source: Palmieri et al. 2020, Reviews on Environmental Health Link to this fact
Health effects / Self-reported survey
In a small lab study, MCS patients exposed to increasing concentrations of the odorant n-butanol reported more intense odors, had higher heart rates, and reported more symptoms over time than healthy controls, with no difference in respiratory rate or skin conductance.
Weak evidence: Secondhand from a single study (Andersson et al. 2016, 18 patients/18 controls) not independently read; small single-lab sample.
Source: Palmieri et al. 2020, Reviews on Environmental Health Link to this fact
Health effects / Measured in people or real products
A case report found a woman with a gain-of-function mutation in the Nav1.7 sodium channel (SCN9A gene) had unusually high olfactory sensitivity along with very low pain, thermal, and tactile thresholds in the nose and lower legs, showing a genetic mechanism can raise smell sensitivity and pain sensitivity together.
Weak evidence: A single case report (one 50-year-old woman); cannot establish how common this mechanism is among MCS patients generally, who mostly do not carry this specific mutation.
Source: Palmieri et al. 2020, Reviews on Environmental Health Link to this fact
Health effects / Review of other studies
A review proposes that TRPV1 and TRPA1, chemical-sensing nerve receptors in the nose, airway, and elsewhere, become upregulated and sensitized (a lower threshold and bigger response to normally tolerated triggers) in both neurodegenerative disease and multiple chemical sensitivity, following long-term exposure to air pollution, oxidative stress, and inflammation.
Weak evidence.
Caveats
Narrative, not systematic review; mechanism is a synthesis of others' receptor biology, oxidative-stress, and imaging studies, not new experimental data; shares its primary capsaicin-challenge evidence base with Molot 2023 (a single small, unreplicated Gothenburg research lineage).
Source: Molot 2022, Reviews on Environmental Health Link to this fact
Health effects / Review of other studies
People with multiple chemical sensitivity do not show the brain-mass loss or olfactory-nerve damage seen in neurodegenerative diseases such as Alzheimer's or Parkinson's; instead, brain-imaging studies find altered processing of odors without evidence of nerve damage, while trigeminal-nerve sensitization is the feature specific to MCS.
Weak evidence.
Caveats
Based on a qualitative present/absent/unknown comparison table (the review's Table 2) built by the authors, not a quantitative meta-analysis; no inter-rater or per-cell sourcing detail given.
Source: Molot 2022, Reviews on Environmental Health Link to this fact
Health effects / Review of other studies
A clinical allergist's practice review proposes that idiopathic environmental intolerance (IEI, formerly multiple chemical sensitivity) commonly involves a genetic anxiety/panic-disorder predisposition and a classically conditioned pairing of specific odors with physiologic sympathetic arousal, citing IEI patients' panic-like responses to sodium lactate infusion and CO2 inhalation challenges and an elevated frequency of a panic-disorder-associated cholecystokinin B receptor allele in a pilot study.
Weak evidence.
Caveats
Built almost entirely on the same author's own small, largely unreplicated 1990s-2000s pilot studies from one Toronto clinic; the paper does not cite or engage the TRPV1/TRPA1 capsaicin-cough-hypersensitivity evidence for a peripheral biological mechanism.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
Health effects / Measured in people or real products
In a small genetic study of 6 people with multiple chemical sensitivity and 5 controls, every single MCS patient carried at least one rare, homozygous variant in a gene from the SLC "solute carrier" transporter family, compared to only 1 of 5 controls.
Weak evidence.
Caveats
Single unreplicated pilot cohort (n=11 total); at least 8 uncorrected statistical comparisons across four gene groups; no odds ratios or effect sizes reported for any variant; no independent replication cohort tested.
Source: Alcorta & Gomez-Diaz 2025, International Journal of Molecular Sciences Link to this fact
Health effects / Test-chamber measurement
In a controlled chamber study, 11 asthmatics with documented bronchial hyperreactivity who breathed a 25 milligram per cubic meter mixture of 22 indoor/occupational VOCs for about 85 minutes had their lung function (FEV1) fall to 90.7% of their pre-exposure baseline, a significant drop from their own baseline.
Weak evidence.
Caveats
The 90.7%-of-baseline decline, while significant vs. the subject's own baseline (p<0.05), was not significantly different from the decline seen after sham (clean-air) exposure (97.4% of baseline); single small study, not independently replicated.
Source: Harving et al. 1991, American Review of Respiratory Disease Link to this fact
Health effects / Test-chamber measurement
The size of the FEV1 decline during the 25 mg/m3 VOC exposure tracked each asthmatic subject's baseline bronchial hyperreactivity to histamine: the more hyperreactive the person, the larger the lung-function drop.
Weak evidence: Secondary correlation analysis within a single small study (n=11); not independently replicated.
Source: Harving et al. 1991, American Review of Respiratory Disease Link to this fact
Health effects / Test-chamber measurement
Breathing the VOC mixture did not change asthmatic subjects' bronchial reactivity to histamine afterward, and no delayed (late-phase) breathing symptoms appeared in the following 24 hours at any dose tested.
Weak evidence: Single small study; absence of a late reaction in 11 subjects over one exposure each does not rule out delayed effects with repeated or prolonged exposure.
Source: Harving et al. 1991, American Review of Respiratory Disease Link to this fact
Health effects / Test-chamber measurement
In a controlled human chamber study, 14 healthy young men who breathed a 25 milligram per cubic meter mixture of 22 everyday indoor VOCs for 4 hours showed a significant increase in nasal inflammatory cells (neutrophils) compared to breathing filtered air, both right after exposure (roughly 2-fold, read from a chart) and, more strongly, 18 hours later (roughly 8-9-fold, read from a chart).
Weak evidence.
Caveats
Single small study (n=14, one lab); a much larger, later study using the identical outcome measure (nasal-lavage neutrophils) at a similar dose (Laumbach et al. 2005, n=130) found no change at all, an unresolved contradiction. The full-cohort magnitude figures are approximate, read from a bar chart, not printed numbers.
Source: Koren et al. 1992, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Test-chamber measurement
A subgroup analysis restricted to the 9 subjects with a low pre-exposure baseline neutrophil count found the same pattern on exact, table-reported numbers: nasal neutrophils rose from 1.4 to 16.0 (times 10,000 cells) immediately after VOC exposure and to 67.6 eighteen hours later, versus no comparable rise after breathing filtered air.
Weak evidence: Small subgroup from a single small study; not independently replicated.
Source: Koren et al. 1992, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Test-chamber measurement
The nasal-inflammation response to the VOC mixture was concentrated in a small number of high-responder subjects (4 of 14), while about half the group (7 of 14) showed minimal or no response to the same exposure — consistent with survey findings that only a minority of people report sensitivity to indoor VOCs.
Weak evidence.
Caveats
Individual-subject pattern from a single small study; the authors themselves note it would need to be tested by re-exposing the same high-responder subjects a second time to see if the response is consistent.
Source: Koren et al. 1992, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Self-reported survey
Most of these patients (7 of 10) were already using asthma inhalers or inhaled steroids for their symptoms and reported getting little or no relief from them.
Weak evidence.
Caveats
Small, uncontrolled self-report within a 10-patient case series; consistent with a later, larger figure (8 of 12) from the same research group's 2000 paper and with an independent Canadian clinic's finding on a related condition, but this 1998 figure alone is not a controlled medication-response trial.
Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact
Health effects / Animal study
After three exposures to one fabric-softener brand, mice showed mild lung inflammation (small clusters of white blood cells and fluid buildup in the walls of air sacs) with no eosinophils, but the difference from sham-exposed mice in lung-tissue density and lung weight was not statistically significant.
Weak evidence.
Caveats
The study's own authors describe the finding as 'very mild'; not shown to be dose-dependent, and the quantitative tissue and weight measures did not differ significantly from controls.
Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact
Health effects / Other evidence
People with allergies (atopic, by skin-prick test) showed a significantly larger drop in a small-airway lung-function measure (FEF25-75) than non-atopic people after the highest VOC exposure (50 mg/m3), suggesting they may be somewhat more physiologically sensitive to VOC mixtures at high doses.
Weak evidence.
Caveats
Very small subgroup (n=5 atopic); atopy was not associated with symptom reports or with any other measured outcome, so this does not show that fragrance/VOC respiratory reactions are generally allergic.
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 vitro, the preservative benzalkonium chloride (BAK) — but not latanoprost or timolol at an intraocular-relevant 1:1000 dilution — dramatically increased human lens epithelial cell secretion of PGE2, IL-1alpha, and IL-6 at concentrations as low as 0.2 micrograms/mL (about 0.5 micromolar, a 1000-fold dilution of typical topical eye-drop strength).
Weak evidence.
Caveats
Single unreplicated in vitro study relayed secondhand in this editorial (primary data is Goto et al. 2003, not yet its own evidence base page); actual intraocular BAK concentrations achieved in patients are unpublished, so the clinical relevance of the tested doses is uncertain.
Source: Brandt 2003, citing Goto et al. 2003 (same issue), Archives of Ophthalmology Industry-funded Link to this fact
Health effects / Other evidence
In cultured human trabecular meshwork cells, BAK concentrations as low as 0.00002% — well below the 0.005-0.02% range found in commercial glaucoma drops — significantly reduced cell density and cell growth.
Weak evidence.
Caveats
Single in vitro study; bovine trabecular meshwork cells in a different study required about 50x that concentration (0.001%) to show the same effect, so results vary by species and cell state.
Source: Rasmussen et al. 2014, citing Samples et al. 1989, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
Health effects / Measured in people or real products
In the same chamber study, particles formed when the citrus fragrance chemical d-limonene reacted with ozone tended to shift that same heart-rhythm marker in the opposite direction from candle smoke, at particle levels similar to everyday cleaning or air-freshener use.
Weak evidence.
Caveats
This tendency was not statistically significant on its own versus clean air (HF -7.2%, p=0.41); only its difference from candle smoke's opposite-direction change reached significance (p=0.02, 12-subject paired comparison). Not replicated.
Source: Hagerman et al. 2014, Atmospheric Environment Link to this fact
Health effects / Lab study (cells or chemistry)
BKC aerosol exposure altered secretion of 166 proteins in bronchial epithelial cells (84 up, 82 down); a gene-disease network of the upregulated secreted proteins linked GDF15, MMP1, and VEGFA (each increased two- to three-fold) to atherosclerosis and cardiovascular disease, suggesting inhaled BKC could have a direct, not just stress-mediated, systemic cardiovascular effect.
Weak evidence.
Caveats
This is a novel hypothesis from one cell-culture secretome analysis cross-referenced against disease-association databases (DisGeNET, CTD), not a measured blood biomarker change in an exposed animal or human; the authors describe it as warranting further investigation.
Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact
Health effects / Review of other studies
A trained Labrador retriever accurately identified cancer patients by sniffing their exhaled breath and stool samples in a controlled study.
Weak evidence: Single trained-dog study cited secondhand; not independently replicated at scale in this review.
Source: Kippenberger 2012, Experimental Dermatology Link to this fact
Health effects / Hypothesis
A 2019 minireview proposes that frequent, long-term burning of scented candles in poorly ventilated rooms may increase bladder cancer risk, based on chemicals in candle emissions (PAHs, benzo[a]pyrene, formaldehyde, phthalates) that are separately linked to bladder cancer via occupational and other non-candle exposure routes.
Weak evidence.
Caveats
No case-control, cohort, or biomonitoring study has ever tested candle use against bladder cancer; the authors' own conclusion calls for that study to be done. This is a narrative minireview with no original data.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Health effects / Review of other studies
Formaldehyde, an ingredient of candle fragrances with a low boiling point, is released at high concentration during candle burning, but the authors state there is no known mechanism linking formaldehyde to bladder carcinogenesis.
Weak evidence: Association is explicitly postulated, not mechanistic, per the authors' own text.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Health effects / Review of other studies
Higher urinary MEHHP (a DEHP phthalate metabolite) was correlated with increased urothelial cancer risk in patients with chronic kidney disease; phthalate esters have also been identified in synthetic candle fragrances.
Weak evidence: Single cohort restricted to chronic kidney disease patients, not the general population; not a candle-exposure study; secondhand citation of Huang & Chou 2018.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Health effects / Review of other studies
Benzyl salicylate, BHT, and butylphenyl methylpropional, all found in the tested perfumes, have been shown in other cited research to interfere with estrogenic signaling pathways and may therefore increase breast cancer risk.
Weak evidence: No doses or a quantified risk estimate are given; this is a mechanistic association from cited literature, not a measured increase in breast cancer risk from perfume use.
Source: Tegengif 2022 Link to this fact
Health effects / Lab study (cells or chemistry)
Lilial is extensively metabolized by liver enzymes (via a Phase I cytochrome P450 route) into lysmerylic acid and p-tert-butylbenzoic acid; the study's authors propose that the metabolite p-tert-butylbenzoic acid, not Lilial itself, is the more likely driver of Lilial's reproductive-toxicity classification, since that metabolite is separately reported (in other cited studies) to disrupt lipid metabolism in sperm-producing tissue.
Weak evidence.
Caveats
This is the authors' own proposed explanation built on citation of two other papers (Laue 2020, Hareng 2023, neither yet in this evidence base); the reprotoxic mechanism of the metabolite was not itself tested in this paper.
Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact
Health effects / Other evidence
A case report describes a 66-year-old woman diagnosed with exogenous lipoid pneumonia after inhaling vaporized paraffin from burning candles.
Weak evidence: Single case report; not generalizable evidence of population-level risk.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
Health effects / Other evidence
A screening-level model of a heavy occupational scented-candle exposure (aromatherapy workers, 8 hours a day for 40 years) found a 95th-percentile lifetime lung cancer risk from PAHs alone of 1.20 in a million, marginally exceeding the commonly used 1-in-a-million risk threshold, under the single worst combination of low ventilation and intermediate humidity tested.
Weak evidence.
Caveats
PAH-only estimate (excludes co-emitted benzene, formaldehyde, and particulate matter that would add to total risk); occupational 8h/day/40-year exposure scenario, not typical home candle use; single candle formulation and small chamber; only the 95th-percentile Monte Carlo estimate under the single worst condition exceeded the threshold, not the mean case.
Health effects / Animal study
Ancestral exposure of pregnant rats to the fungicide vinclozolin (100-200 mg/kg/day, by injection) has repeatedly produced reduced sperm count and motility and increased ovarian cysts in the great-grandoffspring generation across several studies from one laboratory, but two industry-linked studies using oral (rather than injected) maternal exposure during the same developmental window found no transgenerational effect at all.
Weak evidence.
Caveats
The negative replication studies (Schneider et al., 2008 and 2013) are affiliated with BASF, a chemical manufacturer, and used a different exposure route (oral vs. intraperitoneal injection) and possibly different effective dose than the positive studies, so route/dose and funding source are both plausible explanations for the disagreement; unresolved as of this review.
Health effects / Animal study
In rats, daily skin application of six commercial perfumes (three original, three counterfeit) for 28 days significantly increased mast cell counts in the liver and in several lung compartments (perivascular, peribronchial, pleural) compared to untreated controls, with no allergic or inflammatory tissue damage seen on routine histology.
Weak evidence.
Caveats
Single animal study (n=12/group Wistar rats), not replicated; effects were inconsistent across the two special stains used and not every perfume produced a statistically distinguished result in every tissue; perfumes were not chemically characterized.
Source: Hananeh 2021, Open Veterinary Journal Link to this fact
Health effects / Animal study
Neither original nor counterfeit perfume increased mast cell numbers in rat skin (the site of direct application) or the heart after 28 days of daily use — the systemic organs (liver, lungs) responded, not the local application site.
Weak evidence.
Caveats
Counterintuitive given topical exposure; the study did not investigate a mechanism (e.g., systemic absorption vs. distant mast cell recruitment) for why the application site itself was unaffected.
Source: Hananeh 2021, Open Veterinary Journal Link to this fact
Health effects / Animal study
The counterfeit perfume F3 produced the largest single effect in this rat study (liver mast cells rose about 13-fold over control, from about 25 to about 319 cells/mm2 by toluidine blue stain), but the other two counterfeit perfumes tested (F1, F2) did not clearly exceed their genuine counterparts on most measures.
Weak evidence.
Caveats
Only 3 counterfeit/genuine pairs tested, purchased from local markets with no independent authentication or chemical fingerprinting of counterfeit status; not a general fake-vs-genuine comparison.
Source: Hananeh 2021, Open Veterinary Journal Link to this fact
Health effects / Measured in people or real products
The only study in this review to measure parabens and PCOS together (39 PCOS women across normal-weight and obese subgroups, 20 controls) found comparably low plasma paraben levels in all groups and no significant association with PCOS.
Weak evidence: One small study; absence of an association in this one reproductive-endocrine endpoint does not establish that parabens have no hormonal effects generally.
Health effects / Review of other studies
Two studies of urinary triclosan and PCOS point in opposite directions: a 2019 study of 123 women (40 PCOS, 83 controls) found no association, while a 2018 study cited in the same review's discussion found PCOS women had significantly higher urinary triclosan and an elevated LH/FSH ratio, with higher triclosan associated with increased odds of PCOS.
Weak evidence: Both are small, single-population, cross-sectional studies; the review counts only the null one among its 15 primaries and does not explain why the positive study was excluded.
Health effects / Other evidence
In two of three reported chemical-intolerance case studies, QEESI Chemical Intolerance and Symptoms scores fell substantially after a home intervention that reduced fragrance and other VOC sources (Case 1: 80→43 and 63→23; Case 3: 74→54 and 59→23, each on a 0-100 scale).
Weak evidence.
Caveats
Open-label, no control group or blinding, cases selected for notable improvement (not representative of the full 37-patient cohort), and symptom change could reflect counseling/expectation effects rather than VOC reduction specifically.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Health effects / Review of other studies
Urinary octocrylene (a UV filter) was significantly associated with PCOS, but only in women with a BMI of 24 kg/m2 or higher (adjusted OR=1.512, 95% CI: 1.043-2.191); benzophenone-3 and homomethyl salicylate showed no association.
Weak evidence: Based on a single Chinese case-control study (Gu et al. 2019); not replicated; no association found or tested in normal-weight women.
Health effects / Review of other studies
The one study testing parabens against PCOS found no association between summed paraben exposure and PCOS.
Weak evidence: Single small study (19 PCOS women, 20 controls); does not rule out effects of individual parabens or other outcomes.
Health effects / Review of other studies
The evidence on triclosan and PCOS is inconclusive: one Chinese study found infertile women with PCOS had significantly higher urinary triclosan than infertile women without PCOS (p=0.0407), while a second Chinese study recruiting from the same hospital in the same period found no association and triclosan below detection in nearly all samples.
Weak evidence.
Caveats
The two studies directly conflict and overlap in recruiting hospital and window (Zhejiang University Women's Hospital, March 2014-August 2015); the null study also found BPA, benzophenone-3, and homomethyl salicylate below detection where other studies in the same review detect them, suggesting a possible assay-sensitivity issue in that study.
Health effects / Other evidence
Assuming a finite, realistic 10 microliter/cm2 application (rather than the undiluted infinite dose actually tested), the study estimated that about 23% of an applied dose of propylene glycol and about 9% of dipropylene glycol would be absorbed through human skin over 24 hours.
Weak evidence.
Caveats
Extrapolated estimate, not a measurement under finite-dose conditions; the authors themselves flag it as an overestimate, and note the propylene glycol (MPG) figure may be further inflated by stratum-corneum retention that occurs under infinite dosing but would not occur at a finite dose.
Source: Fasano 2011, Toxicology in Vitro Industry-funded Link to this fact
Health effects / Self-reported survey
In a small Takasago-funded study of 131 healthy German adults, those exposed nightly for two weeks to a custom fragrance blend reported modestly better self-rated sleep quality than an unscented control group, but wearable sleep trackers found no actual difference in sleep.
Weak evidence.
Caveats
N=38 vs 19 control; non-randomized, preference-selected groups; industry-funded and co-authored with a Takasago employee; no true placebo (sham-odor) control; effect not sustained after exposure stopped.
Source: Li et al. 2025, Scientific Reports Industry-funded Link to this fact
Health effects / Self-reported survey
Diffusing a scent in the bedroom air was linked to better self-reported sleep quality and less next-day tiredness than a pillow spray or no scent at all, in a small industry-funded trial of healthy adults, but this has not been shown to improve sleep as measured objectively.
Weak evidence.
Caveats
N=39 diffuser vs 19 control; one of the two reported p-values (0.052) is above the paper's own significance threshold; non-randomized; no air-quality/VOC measurement of what the diffuser actually released; funded by Takasago Europe.
Source: Li et al. 2025, Scientific Reports Industry-funded Link to this fact
Health effects / Other evidence
Dermatologists consider moisturizer use critical for preventing and treating numerous skin conditions, and regard allergic or irritant contact dermatitis as the only established health risk of moisturizer use.
Weak evidence.
Caveats
This is the study authors' Discussion-section opinion, not a result of the underlying label survey, and not a formal quantitative risk-benefit analysis weighing skin-barrier/disease-prevention benefits against contact-dermatitis risk. It also covers moisturizers only — no equivalent risk-benefit statement for sunscreen specifically (weighing skin-cancer prevention against contact-dermatitis risk) was found in our evidence base or in this pass, so the video's sunscreen half of the claim remains unsupported by our evidence.
Hidden ingredients / Measured in people or real products
Acetaldehyde, a possible human carcinogen (IARC Group 2B), was released by 23 of 42 baby products and was never listed on any label.
Weak evidence: Not quantified; may partly form during 40 C incubation.
Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact
Hidden ingredients / Review of other studies
As early as 2004, a letter in Environmental Health Perspectives warned that fragrances can draw on thousands of chemicals and that most fragranced products had never been tested for human toxicity.
Weak evidence.
Caveats
The '4,000' figure comes from a 1991 book (Ashford & Miller) and describes untested products, not chemicals; later counts run ~3,000. Date 2020, now read as primary, corroborates 'thousands' as the right order of magnitude for the RIFM inventory (~2,600 active + ~3,500 discontinued) and separately states many individual fragrance materials lack toxicity data for standard endpoints — closer to Curtis's 'never tested' claim than any inventory count — but that is about individual chemicals with read-across-fillable data gaps, not about untested products, and does not confirm Curtis's specific '>4,000' figure.
Source: Curtis 2004, Environmental Health Perspectives Link to this fact
Hidden ingredients / Journalism
Laboratory testing commissioned by US campaigners found 38 chemicals not listed on the label across 17 popular fragrances, 14 per product on average, including hormone-disrupting synthetic musks.
Weak evidence: NGO report reproduced in a review; cite Sarantis 2010 directly; primary not in our evidence base.
Source: Sealey 2016 (citing Sarantis 2010, Not So Sexy), Environment International Link to this fact
Hidden ingredients / Other evidence
A 2015 student lab analysis of 12 popular US perfumes and body sprays found 14-33 separate organic chemicals in each product (130 in all), while US law lets the label say just "fragrance".
Weak evidence: Identities are unconfirmed library matches and were never published; counts depend on the detection threshold. Pair with Steinemann 2011 rather than citing alone.
Source: Lee 2015, Young Scientist Journal (Vanderbilt University) Link to this fact
Hidden ingredients / Measured in people or real products
In a university lab test, 3 of 4 cheap generic or dollar-store plug-in air fresheners gave off petroleum-type solvents (alkanes, one with n-hexane) and the fourth was mostly ethanol; none of these adds scent or appears on the package, and the brand-name plug-ins tested showed neither.
Weak evidence: Student journal; one unit per product; identities not confirmed with standards; no amounts measured.
Source: Pino-Delgado 2021 (J Student Res), Journal of Student Research Link to this fact
Hidden ingredients / Government agency
The industry safety panel's own risk calculation for PFOA (a persistent 'forever chemical' associated with PTFE manufacture) in lipstick relies on a single chemical supplier's claim of under 25 parts per billion in the raw material before it is formulated into a product — no actual PTFE-containing lipstick was tested for PFOA.
Weak evidence.
Caveats
The <25 ppb figure and the resulting '755-fold below EPA's advisory' conclusion are worst-case arithmetic on an unverified, pre-formulation raw-material claim, not a measurement of any real cosmetic product.
Source: CIR 2018 Industry-funded Link to this fact
Hidden ingredients / Industry source
PTFE (Teflon) is reportedly used in some cosmetics at concentrations up to 30%, more than double the 13% leave-on maximum cited from the industry-funded Cosmetic Ingredient Review.
Weak evidence.
Caveats
The paper's own use-concentration data for most PFAS ingredients 'differed by orders of magnitude' across sources; the specific source and current-market relevance of the 30% figure could not be verified for this ingest, and it may reflect a patent-claimed rather than marketed formulation.
Source: Balan 2024, Environmental Science & Technology Link to this fact
Hidden ingredients / Other evidence
Antiperspirants can contain 20-45% D5 (cyclopentasiloxane) by weight, and some leave-on hair serums are D5-dominant products.
Weak evidence: Figures come from a cited third-party product survey, not this paper's own chemical analysis of product formulations.
Source: Montemayor 2013, Chemosphere Industry-funded Link to this fact
Hidden ingredients / Review of other studies
Citing Uhde & Schulz (2015), more than 90% of substances in tested fragranced products were not declared on labels, and neither the FDA nor EU authorities have the resources to evaluate ingredient safety in all scented products on the market.
Weak evidence: Secondhand citation of a study not independently read for this evidence base entry.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Hidden ingredients / Government agency
Cosmetics Europe describes its COSMILE Europe database as giving consumers "reliable, verified and scientifically supported information" on almost 30,000 cosmetic ingredients, but its own press release does not name any data source or independent verification method for that content.
Weak evidence: Absence of a stated methodology in this press release does not itself mean the database is inaccurate; it means the accuracy claim cannot be checked from this document alone.
Source: Cosmetics Europe 2023 Industry-funded Link to this fact
Hidden ingredients / Review of other studies
In a 2007 NRDC test of 14 US air fresheners, 12 (86%) — including some labeled 'all-natural' or 'unscented' — emitted phthalates at up to 7,307 ppm, and none listed a phthalate on the label.
Weak evidence.
Caveats
NRDC 2007 is gray literature (an advocacy-group test, not peer-reviewed) and is not itself in our evidence base; this relays it secondhand through a 2017 review. Only 14 products tested, almost 20 years ago, so 86% is not a figure for the current market or for air fresheners in general. Peer-reviewed testing (Dodson 2012) separately confirms air fresheners are among the highest-DEP product categories, but does not reproduce this specific percentage.
Source: NRDC 2007 (via Steinemann 2017), Building and Environment Link to this fact
Indoor air / Measured in people or real products
In a week-long study of 7 working adults in Leipzig, the air at home made up 42-73% of the airborne chemicals they breathed, more than the outdoor air or their workplaces.
Weak evidence: N=7, one week, 25 VOCs; home share includes infiltrated outdoor air.
Source: Gokhale 2008, Science of the Total Environment Link to this fact
Indoor air / Measured in people or real products
In a real shower test, limonene in the bathroom air rose to about 80, 150, and 380 ppb as the amount of shower product went up, roughly in proportion to the amount used.
Weak evidence: One participant, one bathroom, PTR-MS; limonene only; peaks last minutes.
Indoor air / Hypothesis
A computer model of a morning shower found fragrance terpenes from the products react with indoor ozone to make formaldehyde (about +4 ppb), other aldehydes, irritant PAN-type nitrates, and a little fine particle matter, even with strong ventilation.
Weak evidence: Modeled (INDCM), not measured; increments are small and last about an hour; water-soluble products may dissolve in shower water, so these are upper limits.
Indoor air / Animal study
A continuously running essential-oil diffuser is now the exposure pattern with an animal result attached to it: continuous ambient lavender exposure advanced puberty in rats, while a larger once-daily nasal dose did not.
Weak evidence: Neither exposure was quantified, so the comparison shows a pattern, not a dose-response; with five animals per group the difference rests partly on one outlier.
Source: Kim & Lim 2022, Journal of Korean Medical Science Link to this fact
Indoor air / Instrument measurement
In a small closed test room, three short bursts of aerosol hairspray pushed fine-particle (PM2.5) readings to about 90 µg/m³, roughly 2.5 times the US 24-hour outdoor standard, though only for minutes.
Weak evidence: Uncalibrated consumer monitor; tiny room; short peak vs 24-h standard; primary spray aerosol, no fragrance characterized.
Indoor air / Measured in people or real products
A fresh, 10-minute-old mixture of limonene and ozone, at concentrations close to the high end measured in real homes and offices, made people's eyes blink significantly more often in a small controlled study, at roughly 2,000 times less limonene than pure limonene alone needs to irritate eyes.
Weak evidence.
Caveats
This is the paper's own LOEL (residual 0.23 mg/m3 limonene + 0.08 mg/m3 ozone, +17%, p=0.003) and was previously mis-cited on our evidence base to Klenø & Wolkoff 2004. Now verified as primary, but the same lab's own comparable re-test of Klenø & Wolkoff 2004 gave a 3.5x smaller effect (12% vs 42%) at nearly identical residual concentrations, and no dose-response held across the paper's own four LOPs mixtures (R2=0.7, ns).
Indoor air / Measured in people or real products
Methacrolein, a known limonene/isoprene ozonolysis product, produced a similarly-sized eye-blink-frequency increase on its own (+18% at 286 ppb) as the freshly reacted limonene-ozone mixture did, supporting the idea that it is reaction products, not parent limonene, that irritate eyes.
Weak evidence.
Caveats
Methacrolein was tested alone, not measured inside the LOPs mixtures, so this is an analogy of magnitude, not a demonstration that methacrolein specifically drives the limonene-ozone effect. Single small study, single lab.
Indoor air / Measured in people or real products
Whether an office air-conditioning filter was new or had been in service for about 10 months made no measurable difference to ozone or particle chemistry, or to occupants' reported symptoms, during ozone-limonene exposure.
Weak evidence.
Caveats
Compares only new vs. moderately used (MERV 13) filters at fixed ventilation/recirculation rates; does not test badly fouled filters or other filter grades, so it should not be read as showing filter replacement is never protective.
Indoor air / Review of other studies
During ordinary house cleaning with bleach, chlorine gas concentrations can peak at up to about 0.5 parts per million, and trichloramine is thought to reach similar concentrations when bleach reacts with ammonia or other nitrogen-containing substances.
Weak evidence: This is the authors citing a separate domestic-cleaner cohort study (their own ref. 15) as background, not a measurement made on the children or homes in this study.
Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact
Indoor air / Measured in people or real products
A single portable air cleaner's benefit reached into a nearby room without its own cleaner, cutting PM2.5 by about 58% and PM10 by about 60% on average, though this secondary-room reduction did not reach statistical significance across the whole sample.
Weak evidence: Overall WSRT p=0.089 (PM2.5) and p=0.114 (PM10) in the secondary room; only the daytime-only comparison was borderline significant (p<0.1).
Source: Lu 2024, Aerosol and Air Quality Research Link to this fact
Indoor air / Lab study (cells or chemistry)
This study's in vitro bronchial-cell BKC aerosol doses used for transcriptomics (40.5-634.8 ng/cm2, derived from real commercial disinfectant concentrations of 0.1-0.4% BKC) are roughly comparable in order of magnitude to independently estimated human nasal-spray epithelial doses from approved BKC-preserved pharmaceutical products (about 90-3,020 ng/cm2, per Johnson 2018), unlike many mechanistic-study doses in the wiki that sit orders of magnitude above measured real-world exposure.
Weak evidence.
Caveats
Cross-source, order-of-magnitude comparison only: the product type (disinfectant vs. pharmaceutical), BKC concentration, tissue (bronchial vs. nasal) and deposition model all differ between the two studies, so this is not a validated equivalence.
Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact
Indoor air / Review of other studies
Benzo[a]pyrene levels in fumes from 12 tested scented candles ranged from 0.1 to 7.5 ng/m3, against a WHO guideline value of 1 ng/m3.
Weak evidence: Secondhand citation from this review (Orecchio 2011 not independently read for this evidence base); not this paper's own measurement.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Indoor air / Review of other studies
Measured benzene and naphthalene concentrations emitted by burning candles were reported below the standards considered to exert a toxic biological effect, while sulfur dioxide and benzopyrene concentrations might exceed recommended values in some tested candles.
Weak evidence: Secondhand summary of multiple chamber studies (Derudi, Orecchio) not independently read for this evidence base; heterogeneous across candle brands/types.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Indoor air / Other evidence
Burning scented candles indoors can release formaldehyde, CO2, and volatile organic compounds at levels above indoor background.
Weak evidence: Cites a secondary source (an air-freshener book chapter) not otherwise in this evidence base; not independently checked here against primary chamber measurements.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
Indoor air / Measured in people or real products
Lighting one scented candle for 5 minutes in an ordinary room raised PM10 near the candle (1.52x baseline, 39.9 ug/m3) and kept PM2.5/PM1 elevated for a full hour 3 m and 6 m away (up to 1.97x baseline, ~26-31 ug/m3), with all measured peaks staying below Korea's 24-hour indoor air quality guideline (100 ug/m3 PM10, 50 ug/m3 PM2.5).
Weak evidence.
Caveats
Pilot study of 3 residential houses, one unspecified scented candle burned once for 5 minutes; no replication across candle types, scents, or house configurations, and no chemical (VOC/PAH) measurements.
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
Finer particles (PM2.5, PM1) from a lit scented candle did not simply decay with distance: their concentration kept rising over the hour measured at 3 m and 6 m from the candle, while PM10 peaked and declined fastest at the candle itself, consistent with warm particle-laden air traveling along the ceiling into adjacent spaces (the Coanda effect).
Weak evidence.
Caveats
Single pilot measurement per location per house (3 houses); mechanism (Coanda effect) is the authors' interpretation, not directly visualized or measured (e.g., no airflow tracer or thermal imaging).
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
After lighting a scented candle, a nano-sized bacterial extracellular vesicle population (Phyllobacterium myrsinacearum n-ABE) rose from a minor pre-burn component to 23.8-24.0% relative abundance at the candle spot and 6 m away, the first reported detection of this species' extracellular vesicles in indoor air; the authors attribute this to heat/combustion-triggered growth or apoptosis of the existing airborne bacterial population, not a new bacterial source.
Weak evidence.
Caveats
Single pilot study (3 houses), no independent no-candle control run in parallel (before/after design only), no health-outcome or exposure-dose measurement, and the growth-vs-apoptosis mechanism is the authors' proposed interpretation rather than a directly demonstrated causal pathway.
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
In the one NASA 1989 defoliation test (Marginata, benzene), the plant with all its leaves cut off removed slightly MORE benzene from the sealed chamber over 24 hours (70%) than the same species with full foliage (66%), suggesting root/soil microorganisms, not leaves, did most of the removal.
Weak evidence: Single species tested this way (n=1 comparison), report itself says the mechanism 'cannot be fully explained at this writing'.
Source: Wolverton 1989 Link to this fact
Indoor air / Measured in people or real products
Thermal degradation and combustion of styrene-containing polymers (such as polystyrene) releases styrene into the air; in one measurement of smoke from municipal structural fires, styrene along with benzene, toluene, naphthalene, and 1,3-butadiene accounted for 31% of total VOC concentration.
Weak evidence.
Caveats
Single cited study (Austin et al. 2001) of structural-fire smoke, not candle combustion or routine household conditions; IARC 2019 does not discuss candles specifically and this should not be extended to a candle-specific claim.
Source: IARC 2019 (Vol. 121) Link to this fact
Indoor air / Government agency
EPA warns that overwatered indoor houseplants can promote growth of microorganisms in the soil that may affect allergic individuals.
Weak evidence: Assertion, no measurement or citation given.
Source: US EPA, "The Inside Story" Link to this fact
Indoor air / Review of other studies
Diethyl phthalate (DEP), the phthalate most consistently tied to fragrance use, has been detected in household dust in a German study, alongside the plasticizer phthalates DEHP, DINP, and DBP.
Weak evidence.
Caveats
Relayed secondhand through Crinnion 2010, a narrative review in a naturopathic-medicine journal already flagged elsewhere in this evidence base for reproducing outdated/imprecise figures; the underlying German house-dust study itself is not in our evidence base and has not been checked directly. Presence in dust does not establish that fragrance products (rather than other DEP sources, e.g. plastics) are the dust's source, and does not establish an ongoing-exposure mechanism or a health effect.
Source: German house-dust study, via Crinnion 2010, Alternative Medicine Review Link to this fact
The industry / Journalism
The first press coverage of a 2011 study finding 133 undisclosed chemicals in 25 best-selling scented products, in the US government's environmental-health journal, quoted no manufacturer or industry group; the underlying numbers should be cited from the study itself (Steinemann 2011).
Weak evidence: Media-coverage note only; all product numbers belong to the primary src-2011-fragranced-consumer-products-chemicals-emitted-ingredients-unlisted.
Source: Potera 2011 (EHP news), Environmental Health Perspectives Link to this fact
The industry / Review of other studies
The fragrance industry's answer to autoxidation is to add antioxidants to linalool and linalool-rich natural extracts, but the Gothenburg researchers say that protection is hard to control.
Weak evidence: Industry practice via personal communication from a RIFM scientist (A. M. Api) in a RIFM co-funded paper; no data on effectiveness.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
The industry / Animal study
Two common fragrance ingredients, hexyl and benzyl salicylate, may test positive in the mouse skin-allergy assay not because they are true human sensitizers, but because of a mouse-specific irritant/pharmacological effect, similar to a known false-positive detergent (sodium lauryl sulfate).
Weak evidence.
Caveats
A hypothesis proposed by structural-alert absence and analogy only; the paper offers no direct evidence (e.g., a biomarker distinguishing true haptenation from irritant-driven lymph node activity) and the underlying data are RIFM's own unpublished proprietary dataset.
Source: Roberts & Api 2018, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Review of other studies
The detergent industry's own risk assessment for esterquat fabric softeners sets a margin of exposure of about 8,100 (NOAEL 300 mg/kg bw/day vs. an aggregate consumer exposure estimate of 36.9 micrograms/kg bw/day) and concludes esterquats in fabric conditioner are safe for consumer use.
Weak evidence.
Caveats
Every number comes from the industry's own unpublished, unnamed studies with no independent citation trail; the exposure model covers only dermal and minor oral routes (no inhalation route at all, despite fabric conditioner being used in heated dryers); no carcinogenicity study and no multigeneration reproductive study exist for esterquats — the 'safe' conclusion infers these endpoints are unnecessary from adjacent negative results rather than testing them directly.
Source: HERA Project 2008 (A.I.S.E./CEFIC) Industry-funded Link to this fact
The industry / Review of other studies
The author of a 2023 clinical review arguing that chemical sensitivity is primarily psychogenic (not caused by product chemistry) previously received partial, later-withdrawn funding for an uncompleted IEI genetics study via an unrestricted grant from the Research Institute for Fragrance Materials, the fragrance industry's own research and trade body.
Weak evidence.
Caveats
The funding is disclosed by the author, was withdrawn before the study was completed (due to poor enrollment, not a documented data or conclusions issue), and does not by itself invalidate the paper's clinical arguments; it is a conflict-of-interest fact worth weighing, not proof of bias in this specific manuscript.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
The industry / Review of other studies
This commentary on benzalkonium chloride's adverse effects on the nasal mucosa was funded by an educational grant from AstraZeneca USA, a pharmaceutical company with a commercial interest in intranasal corticosteroid products, which the same commentary recommends as the preferred alternative to decongestant sprays for allergic rhinitis.
Weak evidence.
Caveats
Funding disclosed in the acknowledgment; the underlying rhinostereometry trials (1995-1996) predate this 1999 funded commentary, so only the commentary's framing/synthesis, not the trial data, is implicated.
Source: Graf 1999, Clinical Therapeutics Industry-funded Link to this fact
The industry / Other evidence
This review of BAK's harms to the trabecular meshwork was partly funded by Merck, Inc., and its senior author, Paul Kaufman, discloses paid consultant, honoraria, and financial-support relationships with Alcon and Allergan, both manufacturers of BAK-free alternative eye-drop preservatives (SofZia and Purite respectively) that the review discusses favorably.
Weak evidence.
Caveats
This is a conflict-of-interest disclosure, not an evidentiary finding. The funding pattern runs opposite to a typical 'industry defends its own product' case: the paper argues against a preservative (BAK) while its senior author has financial ties to companies selling competing, BAK-free alternatives.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
The industry / Review of other studies
This benzalkonium chloride pulmonary-toxicity review was written by a single author with no coauthors and no named funding source, who is the principal of a private toxicology consultancy (Pharma Toxicology Safety Solutions LLC) whose business is toxicology/regulatory consulting typically for pharmaceutical clients; the article declares no competing financial interests but gives no funding statement either way.
Weak evidence.
Caveats
This is a characterization of authorship and potential conflict of interest, not a toxicology finding; the review's consistent framing (reinterpreting adverse animal/in vitro findings as clinically inapplicable, and concluding regulatory tightening is unwarranted) matches the argumentative pattern common in industry-oriented safety literature, but no direct pharma-company funding or engagement was found or disclosed.
Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact
The industry / Review of other studies
The study authors cite an earlier analysis reporting that some commercially available PTFE powders contained more than 400 ppb of PFOA — 16 times the EU's 25 ppb regulatory limit — indicating PFOA contamination has been found in the market, not only in controlled lab experiments.
Weak evidence.
Caveats
This is a citation within the primary paper (attributed to Larsen et al. 2005, Analyst) that this evidence base has not independently read or verified; no product names, brands, or cosmetic use are identified.
Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact
The industry / Review of other studies
According to an industry report cited in this review, about 75% of scented candles are fragranced with artificial scents because they cost less than natural fragrance materials.
Weak evidence: Cited without an independently checkable primary source in this review; industry-report figure (ref. 48).
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
The industry / Review of other studies
One of this 2024 axillary-dermatitis review's three authors discloses paid consulting, honoraria, or equity relationships with multiple cosmetic- and pharmaceutical-adjacent companies, including the industry-funded Cosmetic Ingredient Review panel.
Weak evidence.
Caveats
Disclosed conflict of interest is at the individual-author level, not a study funding source; the review's factual content was not evaluated differently on this basis, but the affiliation is named for transparency.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
The industry / Other evidence
The US market for scented candles is estimated to be worth approximately $2 billion annually.
Weak evidence: Abstract-only/background figure; sourced from an industry-characterization paper (Ahn et al. 2015) not independently verified in this evidence base.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
The industry / Measured in people or real products
A 2022 Korean study proposes prioritizing the specific hormone-disrupting chemical combinations that most often turn up together in household products, rather than testing chemicals one at a time, for future mixture-toxicity testing and regulatory management.
Weak evidence: This is a testing-prioritization proposal based on ingredient co-occurrence, not new toxicity data showing that any of the proposed mixtures cause harm.
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
The industry / Other evidence
A study by Petry et al. (2014) concluded that, under normal conditions of use, scented candles do not pose known health risks to consumers.
Weak evidence.
Caveats
Petry et al. 2014 is not yet a evidence base primary; its funding/COI has not been independently verified here, though several co-authors and the paper's risk-assessment framing are consistent with fragrance-industry-connected toxicology work. It is one study among several in this same Viewpoint reaching the opposite conclusion (Adamowicz 2019, Derudi 2014, Chandrasekaran 2021).
Source: Singh 2023, Environmental Science & Technology Link to this fact
The industry / Other evidence
An earlier FDA-lab study found that musk xylol, a synthetic musk fragrance ingredient, did move out of a 24-hour skin reservoir and into the bloodstream over time, unlike the self-tanner and hair-dye chemicals in the 2004 follow-up study.
Weak evidence: Cited secondhand from Yourick 2004's discussion; the Hood 1996 primary source has not been independently read and ingested into this evidence base.
Source: Hood 1996, cited in Yourick 2004, Toxicology and Applied Pharmacology Link to this fact
Laws and loopholes / Journalism
As of 2010, the US FTC's Green Guides on environmental marketing claims had not been updated since 1998.
Weak evidence: Outdated: the Green Guides were revised in 2012 (and an update was proposed in 2022); do not use as a current fact.
Source: Dahl 2010, Environmental Health Perspectives Link to this fact
Laws and loopholes / Review of other studies
Fewer than 20% of the roughly 3,000 high-production-volume (HPV) chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Sealey 2016 relays this figure faithfully from Landrigan 2010, but Landrigan 2010's own citation to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks), is not supported: Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints.
Source: Sealey 2016 (citing Landrigan 2010), Environment International Link to this fact
Laws and loopholes / Measured in people or real products
Musk ambrette, banned in the EU for years, was still detected in the blood of 2 of 100 young Austrians tested, and testing the specific lotion and perfume one of them used did not find musk ambrette in the product itself, so the source of the banned chemical could not be pinned down.
Weak evidence.
Caveats
N=2; the tested products were negative for musk ambrette, so contamination, an unlisted supply-chain source, or a different untested product cannot be distinguished; no source identified.
Source: Hutter 2009, Science of the Total Environment Link to this fact
Laws and loopholes / Review of other studies
A leading pediatric environmental-health review states that fewer than 20% of the roughly 3,000 high-production-volume industrial chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Landrigan 2010 attributes this figure to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks): Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints. The citation does not support the specific number or endpoint claimed.
Source: Landrigan 2010, Current Opinion in Pediatrics Link to this fact
Laws and loopholes / Government agency
Allergy UK's product-endorsement page does not disclose who pays for testing or endorsement; it sits under a business-facing URL and ends in a manufacturer submission form, consistent with (but not confirmation of) a manufacturer-initiated, fee-based process.
Weak evidence: Fee/payer structure is inferred from page layout, not stated by the source; do not cite this page for a fee claim.
Source: Allergy UK 2026 Link to this fact
Laws and loopholes / Review of other studies
No law requires manufacturers of scented candles to prove the safety of their products before releasing them onto the market in the US or EU, per the authors.
Weak evidence: General regulatory claim by the review authors, not independently verified against current statute text in this ingest.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Laws and loopholes / Other evidence
Scented-candle manufacturers should be required to disclose indoor-pollution and health risks on labels or packaging under new labeling and packaging laws.
Weak evidence: A policy recommendation with no current legal requirement cited; no such disclosure law exists today per this source.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
Skin allergy / Measured in people or real products
Most patients who reacted to oxidized scent chemicals (58%) also had other fragrance allergies or a history of reacting to fragranced products.
Weak evidence: 31 positive patients.
Skin allergy / Measured in people or real products
People without skin disease reacted to oxidized limonene and linalool as strongly as dermatitis patients.
Weak evidence: Small groups (9 controls per comparison after exclusions).
Source: Bråred Christensson 2009, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Lab study (cells or chemistry)
In lab tests on human skin cells, the oxidized forms of limonene and linalool reshaped the cells' fats in the same way as a classic potent skin allergen (DNFB), a pattern consistent with oxidative stress.
Weak evidence: One cell line, one dose.
Skin allergy / Lab study (cells or chemistry)
In lab tests on reconstructed human skin, oxidized linalool broke down into reactive radicals that bind to skin proteins, which helps explain why linalool becomes an allergen only after it reacts with air.
Weak evidence: Skin model and model thiols; mechanism, not prevalence.
Source: Kuresepi 2020, Chemical Research in Toxicology Link to this fact
Skin allergy / Lab study (cells or chemistry)
In lab tests on human skin cells, the air-oxidized forms of limonene and linalool (the forms that cause fragrance allergy) damaged the fats in cell membranes at concentrations from 100 µM, with oxidized limonene strongest; a possible second route to skin inflammation not yet shown in people.
Weak evidence: Cell line and liposomes only; added iron; real skin doses unknown.
Skin allergy / Measured in people or real products
Once someone is sensitized, patch tests can trigger reactions at low ppm concentrations of oxidized terpene — but the specific 'as low as 1 ppm' figure is for Δ³-carene in older, narratively-reviewed occupational turpentine literature; for the two terpenes that dominate consumer exposure, modern peer-reviewed dose-response studies put the threshold one to two orders of magnitude higher (limonene hydroperoxides: ~24 ppm single patch application, ~140 ppm repeated realistic exposure, ED₁₀ ≈85 ppm; linalool hydroperoxides: ~560 ppm repeated realistic exposure).
Weak evidence.
Caveats
The 1 ppm figure applies to Δ³-carene in historical occupational patch testing, not to limonene or linalool, and its own study design (occlusion, participant numbers) is not given in the citing review. No limonene- or linalool-specific study supports reactions at ~1 ppm.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
All four patients already allergic to oxidized linalool reacted to air-exposed lavender oil on patch testing.
Weak evidence: N=4 pre-selected sensitized patients; fresh oil not tested alongside; elicitation, not sensitization.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Review of other studies
A 2007 clinical review reports that oxidized limonene caused positive patch-test reactions in about 2.6% of dermatitis patients in a European study, leading to a call to add oxidized limonene to routine allergy screening.
Weak evidence.
Caveats
Secondary relay of Matura et al. 2006 (not independently read in this evidence base); this is an early statement of a position later found by other groups (e.g. the IVDK) to over-call weak/doubtful reactions as true allergy.
Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact
Skin allergy / Review of other studies
By 2007, Fragrance Mix II, a newer fragrance patch-test screen, was showing a high and still-rising rate of positive reactions in German clinic data, on top of the original Fragrance Mix I.
Weak evidence.
Caveats
Cites the original FM II validation studies (Frosch et al. 2005) plus an unpublished personal communication (IVDK network) for the 'still increasing in 2007' claim; neither is independently verified here.
Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact
Skin allergy / Review of other studies
People sensitized to hydrolyzed wheat protein in cosmetics do not necessarily react to intact wheat protein, so they can generally still eat wheat/bread without a reaction.
Weak evidence: Stated in passing in a narrative review, citing a single 2006 study; not itself verified against the primary.
Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact
Skin allergy / Review of other studies
In one clinic-based dose study, the paraphenylenediamine concentration that elicited at least a weak positive patch-test reaction in 10% of already PPD-sensitized people was 38 ppm, well below the concentrations permitted for hair dyes — raising the question of whether the standard 1% patch-test concentration is itself safe to apply.
Weak evidence: Threshold applies to already-sensitized individuals in one cited dose-response study, not to the general population's exposure risk; relayed secondhand.
Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact
Skin allergy / Review of other studies
Fragrance is the most common cause of allergic contact dermatitis in the armpit, and deodorants and antiperspirants are a major source of that fragrance exposure.
Weak evidence: Narrative clinical review with no new data of its own; relays a 1982 cosmetic-product survey and later studies not independently re-checked here.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Skin allergy / Review of other studies
Axillary dermatitis can occasionally be caused by systemic contact dermatitis or symmetrical drug-related intertriginous and flexural exanthema (SDRIFE) rather than direct topical contact allergy; in sensitized patients, eating balsam-of-Peru-rich foods (citrus, chocolate, tomato, certain alcohols) can trigger a flare without any new topical exposure.
Weak evidence: Relayed from isolated case reports; systemic contact dermatitis of the axillae is described as rare.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Skin allergy / Other evidence
Across three chemical-intolerance case studies with symptom improvement tied to reduced VOC exposure, blood IgE allergy panels for 16 common indoor/outdoor/food antigens did not track or explain the symptom changes, and only 2 of the full 37-patient cohort (5.4%) had elevated antibodies to both dust mite and cockroach allergens.
Weak evidence.
Caveats
Uncontrolled case-series observation; absence of IgE elevation does not rule out other allergic or non-IgE immune mechanisms, and the paper does not test a specific non-allergic mechanism directly.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Skin allergy / Review of other studies
Fragrance causes both irritant and allergic contact dermatitis, among other adverse skin reactions, and fragrances are the most frequent chemicals causing contact dermatitis overall.
Weak evidence.
Caveats
Narrative review statement, not a ranked prevalence study; does not establish that contact dermatitis (from any cause) is the single most common adverse reaction to skincare products in general, only that fragrance is a leading cause of contact dermatitis specifically and that it can be either irritant or allergic.
Source: Pastor-Nieto 2021, Current Treatment Options in Allergy Link to this fact
Skin allergy / Review of other studies
Fragrance chemicals are also used as food flavorings, and dermatologists consider systemic contact dermatitis from fragrance-related food flavorings in fragrance-allergic patients whose eczema does not clear after 6 weeks of full topical fragrance avoidance.
Weak evidence: Clinical management guidance from a narrative review, not a measured ingestion-exposure or prevalence study; does not quantify how often food flavorings are the actual culprit.
Skin allergy / Review of other studies
Certain fragrance and botanical ingredients have been linked to pigmented cosmetic dermatitis (facial hyperpigmentation), reported mainly in Japan in the 1960s-1970s; the condition became rare after 1978 reformulation of the implicated products.
Weak evidence.
Caveats
Relayed from a narrative review's historical summary (citing older Japanese case-report literature, e.g. Nakayama); no prevalence data or systematic count of cases is given, and a companion evidence base source page (src-2020-review-perfume-present-status-associated-allergens) names specific implicated ingredients (ylang-ylang, jasmine absolute, cananga, benzyl salicylate, hydroxycitronellal, sandalwood, geraniol) but the video's decade range (1970s-80s) is only approximately matched (source says 1960s-1970s).
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
Skin allergy / Other evidence
The National Eczema Association's Seal of Acceptance certification criteria exclude chemical UV-absorber sunscreens, accepting only physical (mineral) sunscreens containing titanium, zinc, or iron oxide.
Weak evidence.
Caveats
This reflects one certification body's precautionary ingredient-exclusion criteria for eczema-prone skin, not measured comparative allergic-contact-dermatitis incidence rates between mineral and chemical UV filters — no such comparative rate data were found in our evidence base or in this pass. Do not read this as evidence that mineral filters cause fewer ACD reactions in the general population, only that this eczema-focused body's rules treat them as the safer default.
Source: National Eczema Association 2026 Link to this fact
What you can do / Measured in people or real products
Childcare rooms with more fresh-air exchange had lower levels of several of the chemicals measured.
Weak evidence: Bivariate correlations, 34 rooms.
What you can do / Measured in people or real products
Keep scented products closed and avoid old, long-opened ones: limonene and linalool became skin irritants after weeks of air exposure.
Weak evidence.
Caveats
Extrapolated from lab-oxidized neat material (10-20 weeks air exposure); product storage not tested by this paper. Two independent industry market surveys have now directly tested the specific mechanism this advice assumes (in-bottle oxidation with age) and both found it absent: Kern 2014 (39 aged fine fragrances + 29 antiperspirants, 9 months accelerated storage) and Natsch 2019 (104 products spanning fine fragrances, antiperspirants, creams, and lotions, including two fine fragrances tracked 3-6 years at room temperature) both found no progressive hydroperoxide accumulation with age, and consumer-product doses 2-4 orders of magnitude below elicitation/sensitization thresholds. Both studies are industry-funded (IDEA consortium: Givaudan, Firmenich, IFF, IFRA) and not independently replicated by a non-industry group, and neither tests essential oils or raw materials (separately known to accumulate hydroperoxide) or every product category. Moved to claims-to-avoid because the specific mechanistic basis for this advice (in-container autoxidation) is now negative in the only two real-product tests that exist, even though the underlying autoxidation chemistry itself, in neat/essential oils, is not disputed. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Bråred Christensson 2009, Contact Dermatitis Industry-funded Link to this fact
What you can do / Review of other studies
Old, long-opened scented products are more allergenic than fresh ones, because the scent chemicals oxidize on contact with air.
Weak evidence.
Caveats
Time course is primary for lavender oil (Hagvall 2008: LLNA EC3 36% fresh -> 23% at 10 weeks -> 4.4% at 45 weeks in the same batch), but in neat oil in open lab flasks, not formulated products as stored. Kern 2014 first closed part of this gap (39 fine fragrances + 29 antiperspirants, no accumulation over 9 months accelerated storage); Natsch 2019 extends this to 104 products across more categories (adding limonene, creams, lotions) and to multi-year real-time storage (two fine fragrances tracked 3-6 years at room temperature, no accumulation), plus tests products donated by allergic patients themselves (also negative for hydroperoxide). Downgraded to avoid because the specific claim — that aging/opening itself makes a product more allergenic via in-container oxidation — has now failed two independent, broader industry market surveys with no non-industry evidence on the other side; creams, lotions, and fine fragrances/antiperspirants are covered, though essential oils, raw materials, and other categories remain untested and are not covered by this downgrade. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
What you can do / Self-reported survey
People affected by fragrance say policies work only with purchasing rules for fragrance-free, low-emission products, staff education, better ventilation, and consequences for repeat violations, enforced like smoke-free rules.
Weak evidence: Participants' and authors' proposals; not tested as an intervention.
Source: Roy 2026 Link to this fact
What you can do / Hypothesis
Air a room or clean it instead of scenting it: non-chemical alternatives such as opening windows and better hygiene are the first step in Klaschka's ten-step hierarchy for reducing fragrance exposure.
Weak evidence: Expert recommendation; not tested in the paper.
Source: Klaschka 2020, Environmental Sciences Europe Link to this fact
What you can do / Review of other studies
If a child develops unexplained breast tissue, tell the doctor about every scented product the child uses or is near, including colognes, baby washes, hair products, and diffusers; stopping them is what the case reports did.
Weak evidence: Practical advice drawn from case reports, not a tested intervention.
Source: Hawkins 2020, Complementary Therapies in Medicine Industry-funded Link to this fact
What you can do / Self-reported survey
People who always or usually used a healthy-product app, read ingredient labels, or looked for eco-friendly labels used hair, skin, and beauty products with somewhat lower EWG hazard ratings, by up to half a point on a 10-point scale.
Weak evidence: Cross-sectional; the rating is built from the same labels, so it cannot see undisclosed fragrance chemicals; no exposure measured.
Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact
What you can do / Measured in people or real products
Using less shower product and running the bathroom fan both lower the fragrance-terpene peak: emissions scaled with product amount, and halving ventilation raised the modeled limonene peak from about 375 to 495 ppb.
Weak evidence: Amount-scaling from one person's shower; ventilation effect is modeled; no health outcome measured.
What you can do / Test-chamber measurement
Keeping indoor ozone low (no ozone-emitting 'air purifiers' or ionizers) limits both skin-oil chemistry and fragrance-terpene chemistry indoors, because ozone starts both chains.
Weak evidence: This paper makes no recommendation; the ozone-generator advice comes from Singer 2006, and the ventilation/ozone trade-off is our inference.
What you can do / Review of other studies
If you want to avoid persistent fluorinated ingredients, check cosmetic labels for 'PTFE', 'polytetrafluoroethylene', or names containing 'perfluoro-' or 'polyfluoro-'.
Weak evidence.
Caveats
Namazkar 2024 found INCI names for PFAS ingredients can themselves be ambiguous or incorrect (an apparent isomer mismatch for a silane; an undisclosed shorter chain-length range for a phosphate ester), and found unlabeled residual PFCA impurities in nearly every PFAS-containing cosmetic tested (5 of 6 products), which were far more dermally bioaccessible (43-76%) than the labeled ingredient itself (negligible bioaccessibility). Label-reading is a reasonable screen for intentionally added, correctly-named PFAS but does not detect the unlabeled residual impurities this paper shows can be present and bioaccessible regardless of which PFAS is named.
Source: Jomaa 2024, Journal of the Netherlands Society of Toxicology (JNST) Industry-funded Link to this fact
What you can do / Lab study (cells or chemistry)
Only 6 of 42 perfumes tested were comparatively low in hazardous compounds across ten lab tests, which suggests lower-hazard perfumes can be made.
Weak evidence: Products not named, so consumers cannot identify the cleaner ones; in vitro only.
Source: Morlock & Heil 2025, Journal of Chromatography A Link to this fact
What you can do / Instrument measurement
A filter-only HEPA air purifier kept fine-particle readings near zero after hair and nail products were used together in a small closed room.
Weak evidence: Flow-to-volume ratio far above any real home or salon; VOC removal by the carbon filter not credible for acetone/formaldehyde.
What you can do / Review of other studies
Fragrance-free policies are easier to make work when they start with a needs assessment and an inventory of the cleaning and personal products in use, involve employees in drafting, and agree how violations are handled before launch.
Weak evidence: Lessons from unnamed organizations; no outcome data.
What you can do / Review of other studies
Close fragranced products after use and discard them about a year after opening to limit exposure to oxidized allergens.
Weak evidence.
Caveats
Expert advice; no study tests whether it reduces dermatitis. The assumed mechanism (in-bottle oxidation during storage) has now failed two industry market surveys rather than one: Kern 2014 (fine fragrances, antiperspirants, 9 months accelerated storage) and Natsch 2019 (104 products including creams and lotions, two fine fragrances tracked 3-6 years at room temperature) both found no hydroperoxide accumulation with age or storage time. The advice may still be reasonable for essential oils and raw materials (which do carry hydroperoxide, e.g. lavandin ~220 ug/g), just not via this specific in-bottle mechanism for finished consumer products. Both studies are industry-funded (IDEA consortium: Givaudan, Firmenich, IFF, IFRA) and not independently replicated, and say nothing about essential oils, raw materials, or product categories outside fine fragrances/antiperspirants/creams/lotions. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Pastor-Nieto 2021 (Klaschka 2010), Current Treatment Options in Allergy Link to this fact
What you can do / Measured in people or real products
Moisturizers that listed alcohol or 'alcohol denat.' near the top of the ingredient list delivered far more ethanol to a mannequin's nose; products with no listed alcohol gave almost none.
Weak evidence: 16 products, qualitative (Fig. 4, no statistic); ethanol hidden inside 'parfum' is not visible on labels; absolute ethanol doses are disputed.
What you can do / Measured in people or real products
'Agua de violetas' colognes marketed to Hispanic families, including preparations made for babies, are a specific consumer product worth asking about if a young child has unexplained breast growth.
Weak evidence: Based on 2 of 3 case reports from one clinic; not every bottle sold under this name contains lavender oil.
Source: Diaz 2016, Journal of Pediatric Endocrinology and Metabolism Link to this fact
What you can do / Hypothesis
If you already notice fragrance-related symptoms, do not expect awareness alone to change your exposure — most Germans who link their own symptoms to fragrance still use fragranced products at or above the average rate; choosing fragrance-free products and spaces is the step that actually reduces exposure.
Weak evidence: Author's recommendation, drawn from the self-exposure paradox in this survey; not itself tested as an intervention.
Source: Klaschka 2020a, Environmental Sciences Europe Link to this fact
What you can do / Review of other studies
If households switch from fragranced to fragrance-free laundry detergent, modeling suggests dryer-vent limonene emissions across a whole city or state could drop substantially — an estimated 1.58 tons per year for metropolitan Melbourne, or 8.66 tons per year for the state of California.
Weak evidence.
Caveats
This is a modeled extrapolation, not a measurement: it multiplies a mean vent concentration from just 2-6 households (one grab sample each) by census household counts and usage-rate assumptions, with no confidence interval or sensitivity analysis anywhere in the calculation; the Melbourne input is dominated by a single outlier household roughly 11 times the other three.
Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact
What you can do / Review of other studies
Wearable personal chemical-exposure monitors with audible threshold alarms ("eNose"-type devices) are proposed as a future tool to help people track real-time chemical exposure and correlate it with symptom onset, alongside biomarker testing (blood/urine for substances or metabolites) when intoxication is suspected.
Weak evidence.
Caveats
A forward-looking recommendation in the review's discussion/outlook section, not a validated or clinically deployed diagnostic tool; no accuracy, sensitivity, or outcome data for any such device is cited.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
What you can do / Review of other studies
Because people with MCS describe both a fear of asking for accommodations (risking hostility) and a fear of staying silent (risking worsening symptoms), workplaces and services that proactively offer fragrance-free accommodation without requiring the person to ask remove one source of this dilemma.
Weak evidence.
Caveats
Qualitative theme ('suppressing vs expressing needs', 9 findings/5 studies) describing participants' experience, not a tested intervention; no study in this review evaluated an accommodation policy's effect. Downgraded moderate→weak 2026-09-27 (Jev audit): the accommodation recommendation is an inference, not a finding.
Source: Driesen 2020, Journal of Psychosomatic Research Link to this fact
What you can do / Measured in people or real products
A small trial found that a nasal spray containing hyaluronic acid, used daily for a month, reduced smell-detection thresholds and improved smell-disorder and anxiety questionnaire scores in MCS patients compared with a saline spray.
Weak evidence: Single small trial (29 treated/30 controls per this review's own Table 1) from one research group, not independently replicated; not an approved or established MCS treatment.
Source: Palmieri et al. 2020, Reviews on Environmental Health Link to this fact
What you can do / Review of other studies
For people whose fragrance/chemical reactions have a strong anxiety or panic component, mental-health referral, stress management, relaxation training, graded psychological desensitization to trigger odors, and (if needed) low-dose SSRIs are a recommended management approach, used alongside (not instead of) ruling out and treating any real underlying allergic or respiratory disease.
Weak evidence.
Caveats
The author states outright that research on mental-health treatment efficacy specifically in IEI is limited, because many affected patients decline psychiatric referral; the recommendation rests on case reports and phobia-treatment analogy, not controlled trials in this population.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
What you can do / Test-chamber measurement
Accurate, calibrated information about a real chemical exposure (e.g., explaining that mild effects now do not imply long-term harm) can reduce reported irritation and symptoms compared with giving no information at all.
Weak evidence.
Caveats
Single lab study of naive volunteers under brief controlled exposure; may not generalize to real workplaces, longer exposures, or people who already have symptoms from an exposure. Downgraded to weak 2026-09-28 (Jev audit): the action goes beyond what this paper itself tested.
Source: Dalton et al. 1997, Int Arch Occup Environ Health 69:407-417 Industry-funded Link to this fact
What you can do / Measured in people or real products
People whose breathing symptoms are triggered by scents or chemical irritants, but whose standard asthma tests (spirometry, methacholine challenge) come back normal, can ask a specialist about objective sensory-hyperreactivity testing, such as a capsaicin cough-sensitivity challenge, rather than assuming the symptoms are either undiagnosed asthma or purely psychological.
Weak evidence: Capsaicin cough-challenge testing is a research protocol developed and used mainly by this one Swedish research group, not a routine or widely available clinical test.
Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact
What you can do / Government agency
As of 1998, EPA planned to expand its voluntary consumer-labeling initiative beyond pesticides to labels on household and other consumer products such as cleaning agents and latex paint, aiming to give clearer hazard information, especially for children.
Weak evidence.
Caveats
A stated 1998 plan/intention, not a completed program; the paper does not report whether or how it was implemented, and no fragrance-specific labeling requirement is described anywhere in the paper.
Source: Goldman 1998, Environmental Health Perspectives Link to this fact
What you can do / Review of other studies
Close deodorant containers after use and replace them about a year after opening: two of the most common deodorant fragrances (limonene, linalool) are rated weak allergens fresh but oxidize in air into much stronger sensitizers.
Weak evidence.
Caveats
Klaschka relays this oxidation chemistry from prior studies (Karlberg 1994, Matura 2005, Skold 2008), already in our evidence base; she adds no new dose data of her own. Downgraded to weak 2026-09-28 (Jev audit): the action goes beyond what this paper itself tested.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
What you can do / Other evidence
Because the association tracked frequency of use in a dose-response pattern, using fewer personal care products or using them less often is the lowest-regret step for someone concerned about a possible link to lung function.
Weak evidence: The study did not test whether reducing use reverses any effect; this is an inference from an observational dose-response pattern, not a tested intervention.
Source: Dales 2013, Annals of Epidemiology Link to this fact
What you can do / Measured in people or real products
Running an ozone-generating device (an ionizer, or some 'air purifiers') at the same time as using citrus- or terpene-scented cleaning or personal-care products creates the same class of reaction-product nanoparticles studied here; keeping the two apart in time, or ventilating, avoids generating them.
Weak evidence.
Caveats
This study alone did not find a significant health effect from the terpene+ozone arm; the precautionary action is supported by the wider ozonolysis-SOA literature in our evidence base (see transformation-products), not by this study's HRV result in isolation. Downgraded to weak 2026-09-28 (Jev audit): the action goes beyond what this paper itself tested.
Source: Hagerman et al. 2014, Atmospheric Environment Link to this fact
What you can do / Other evidence
Because leave-on skin products with large use amounts (body lotion, fine fragrance) drove the highest modeled fragrance-ingredient exposure in this industry model — not air-care products, which had the highest in-product concentrations but low exposure due to no skin contact — a reasonable consumer heuristic is that layering multiple fragranced skin products likely matters more for aggregate systemic fragrance exposure than using a scented candle or air freshener.
Weak evidence.
Caveats
Derived inference from a single industry model covering 8 ingredients; not validated against measured exposure; does not address inhalation health effects, only relative modeled systemic dose.
Source: Safford 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
What you can do / Hypothesis
Unlike outdoor air pollutants such as vehicle exhaust, people can directly reduce their exposure to limonene at home by limiting use of strongly limonene-scented personal-care products and household cleaners.
Weak evidence: This is the authors' own inference from a cross-sectional association, not a tested intervention; no randomized avoidance trial has been done, though the authors call for one.
Source: Dales & Cakmak 2019, Environmental Pollution Industry-funded Link to this fact
What you can do / Lab study (cells or chemistry)
People on long-term BAK-preserved eye drops (e.g., for glaucoma or dry eye) with ocular surface concerns may want to ask their prescriber about preservative-free formulations.
Weak evidence.
Caveats
Based on an in vitro cell-culture study, not a clinical trial; supports a conversation with a prescriber, not a self-directed switch, and does not establish that any specific preservative-free product (including the study's own TBE formulation) is proven safer in practice.
Source: Kabashima 2020, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
What you can do / Measured in people or real products
Powder laundry detergents had the lowest average common-allergen count of any subgroup surveyed (0.75/product) and contained none of the preservative allergens (MI, BIT, MCI/MI, phenoxyethanol) tracked in this study; their only common allergen was fragrance, present in 3 of 4 products.
Weak evidence: Very small subgroup (n=4); one 2019 US best-seller sample, not necessarily generalizable to all powder detergents.
What you can do / Measured in people or real products
Regularly cleaning a dryer's lint trap and keeping vent ducting short and well-maintained is associated with differences in how much microfiber reaches the outside vent, based on comparing two homes with different dryer ages and duct setups.
Weak evidence.
Caveats
This is a two-home comparison, not a tested intervention — the study did not clean or modify ducting and measure a before/after change, so this is an inference from correlation, not a demonstrated fix.
Source: Kapp & Miller 2020, PLOS ONE Industry-funded Link to this fact
What you can do / Measured in people or real products
Keeping candles away from drafts, fans, open windows, and foot traffic that make the flame flicker can substantially cut soot, fine-particle, and particle-bound PAH exposure, since flame disturbance alone (independent of which candle is burned) was the single largest factor increasing these emissions in this chamber study.
Weak evidence.
Caveats
Based on chamber simulation of flame disturbance via a rotating fan, not a home-scale test of specific draft sources; does not address NOx or formaldehyde exposure, which were unaffected by burn disturbance in this study. Graded weak: what-you-can-do resting on one chamber study.
What you can do / Review of other studies
Because this industry classification describes average sensitization thresholds measured in previously unexposed volunteers, not the much lower doses that can trigger a reaction in someone already allergic, a patch-test-confirmed fragrance-allergic consumer should avoid a flagged chemical entirely rather than assume any low listed concentration is safe for them personally.
Weak evidence.
Caveats
This point is not stated by this paper itself; it follows from this evidence base's existing analysis (register entry C112) of the induction-versus-elicitation gap in fragrance industry risk assessment generally.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
What you can do / Lab study (cells or chemistry)
Patients on long-term BAC-preserved eye drops (e.g., for glaucoma) who have corneal or ocular-surface concerns can ask their prescriber about preservative-free alternatives.
Weak evidence.
Caveats
This is a discussion-with-clinician action, not a claim that BAC-preserved drops are unsafe at typical clinical use; based on an in-vitro model plus prior clinical ocular-surface-disease literature the paper cites, not a clinical trial of this specific outcome. Graded weak (orchestrator): in-vitro, 2-donor study alone.
Source: Umetsu et al. 2024, Graefe's Archive for Clinical and Experimental Ophthalmology Link to this fact
What you can do / Measured in people or real products
People patch-tested positive to isoeugenol or Fragrance Mix I should avoid isoeugenol-containing deodorants entirely rather than relying on IFRA-compliant "low" concentrations, since the current 0.02% cap sits inside the range this study showed can elicit reactions in sensitized users.
Weak evidence: Extrapolated consumer advice from a clinical elicitation study; not itself a tested intervention. Graded weak: what-you-can-do resting on one small ROAT study.
Source: Bruze et al. 2005, Contact Dermatitis Link to this fact
What you can do / Lab study (cells or chemistry)
Choosing a roll-on or stick deodorant instead of a spray from the same product line may reduce exposure to the estrogen-active fragrance ingredients this one lab's testing found concentrated in sprays.
Weak evidence.
Caveats
Rests on a single lab's testing of 25 German products; dispenser-type differences most likely reflect how much fragrance a given carrier formulation needs, not a demonstrated safety difference, and this has not been independently replicated or linked to any human exposure or health outcome.
What you can do / Measured in people or real products
Keeping a scented candle unlit doesn't necessarily stop it from adding VOCs to a room's air — one product in this study off-gassed heavily even unlit, so if you want to avoid a candle's chemical emissions, removing the product from the room (not just leaving it unlit) is what this data suggests actually helps.
Weak evidence.
Caveats
Based on one lab's measurements of six specific products in Korea; whether unlit off-gassing in an actual room reaches similar relative levels to what was measured in this study's small chamber has not been tested here.
Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact
What you can do / Review of other studies
Ventilate rooms during and after burning scented candles, and prefer higher-quality or unscented candles over cheap paraffin-based scented ones, as a general precaution against indoor chemical accumulation.
Weak evidence.
Caveats
General precaution suggested by the review authors; rests on this single hypothesis paper's synthesis, not on a study measuring outcomes from these actions, and does not itself establish a bladder-cancer risk reduction.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
What you can do / Animal study
People who work for hours daily near burning scented candles under high job stress (for example, spa, hospitality, or restaurant staff who tend candle displays), rather than casual home users, are the population most directly addressed by this animal model, and may want to reduce burn time or improve ventilation in that specific occupational setting.
Weak evidence.
Caveats
Based on a single small, unreplicated mouse study using an occupational-intensity exposure chamber; no human occupational data were collected, and the specific candle's composition was not disclosed.
Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact
What you can do / Advocacy group testing
This report recommends free consumer apps (Yuka, Tox Fox, Kemiluppen) and trusted ecolabels (Nordic Swan, EU Ecolabel) or fragrance-free certification labels (Asthma Allergy Denmark, Allergy Certified) as ways to identify or avoid suspected EDCs and allergens in personal care products.
Weak evidence: The report does not test whether using these apps or labels measurably reduces a person's chemical exposure or biomarkers.
Source: Tegengif 2022 Link to this fact
What you can do / Self-reported survey
Keeping scented-candle sessions shorter (well under 60 minutes) may reduce symptom risk somewhat, since the longest-duration group (>60 min per session) showed the largest (though not statistically significant) increases in headache, sneezing, and wheezing odds.
Weak evidence.
Caveats
Rests on one small, non-representative, single cross-sectional survey; none of the duration-based odds ratios reached statistical significance (all 95% CIs crossed 1), so this is a plausible precaution, not an established dose threshold.
Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact
What you can do / Lab study (cells or chemistry)
Cold-atmospheric-plasma deodorizing devices are an emerging non-chemical, non-fragrance approach to underarm odor control worth watching as an alternative to conventional antimicrobial/fragranced antiperspirants.
Weak evidence.
Caveats
Based on one prototype tested only against cultured bacteria and porcine skin dosed with synthetic odor compounds; no human trial, no skin-safety or allergy testing, and the device generates ozone (a known respiratory irritant) as part of its mechanism.
Source: Bok et al. 2024, Scientific Reports Link to this fact
What you can do / Other evidence
Airing out a room after burning scented candles helps remove residual chemical compounds produced during burning.
Weak evidence: Common-sense ventilation advice; not independently quantified in this editorial or checked against primary ventilation-effect data in this evidence base.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
What you can do / Other evidence
People should use scented candles with caution in closed spaces and should refrain from using them around vulnerable groups such as pregnant women, children, the elderly, and people with pre-existing cardiopulmonary conditions.
Weak evidence: A precautionary recommendation, not based on a candle-specific dose-response or exposure-outcome study in any of the named vulnerable groups.
Source: Singh 2023, Environmental Science & Technology Link to this fact
What you can do / Other evidence
A structured home walkthrough that identifies and removes common VOC sources (mothballs, scented cleaning and personal-care products, candles, garage-stored chemicals) and separates stored chemicals from living space (e.g., moving gasoline/solvents/paints to detached storage) reduced measured indoor VOC levels in the homes studied.
Weak evidence.
Caveats
Professional testing and a trained team delivered this intervention over 5 visits across a year; the paper does not test which individual component (removal vs. substitution vs. new storage vs. counseling) drove the VOC reduction. Evidence is one small uncontrolled case series.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
What you can do / Review of other studies
Because diet is the main route of human exposure to BPA and phthalates from food packaging, avoiding microwaving food in plastic, cutting back on canned food, and choosing glass, stainless-steel, or aluminum containers instead of plastic can reduce dietary exposure to these obesogenic chemicals.
Weak evidence.
Caveats
This reduces measured chemical exposure; no trial has tested whether making this switch actually changes body weight or obesity risk in people. The review infers this from exposure routes; it cites no intervention study measuring the reduction.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
What you can do / Review of other studies
At least 25% (and likely closer to 50%) of the sunscreen applied to skin washes off during sea bathing, and an estimated 35+ kg of sunscreen is deposited per day for every 1,000 people visiting a single beach, so choosing physical sun protection (clothing, hats, shade) over reapplying sunscreen right before swimming directly reduces this wash-off pathway into marine water.
Weak evidence.
Caveats
Wash-off fraction estimates vary between the cited studies (25% vs approx. 50%); the beach-deposition figure is a modeled estimate, not a direct field measurement of ecological harm This action is the ingest's inference from a review's cited wash-off and modeled deposition figures; no study tested it.
Source: Hodge 2025, Marine Pollution Bulletin Link to this fact
What you can do / Review of other studies
The study's authors argue that reducing DEHP/plastic-related cardiovascular mortality requires regulation (banning or restricting DEHP in products, improving labeling), better waste management, and international cooperation such as the UN's Global Plastics Treaty negotiations, rather than relying on individual consumer avoidance alone.
Weak evidence: This is the authors' policy recommendation; no intervention was tested in this study.
What you can do / Government agency
A patient with fragrance/chemical sensitivity asking a clinic to have staff avoid fragrance for one scheduled appointment is asking for something narrower than a facility-wide rule, and DOJ's 1995 'usually not reasonable' answer was addressed to the broader framing, not this narrower one.
Weak evidence: DOJ never separately analyzed the narrower, one-appointment request; this is an inference from reading the letter against its own attached correspondence, not a DOJ holding.
Source: DOJ TAL605, 1995 Link to this fact
What you can do / Self-reported survey
Perfume is most often sprayed on the neck and throat, then the arms — close to the nose and mouth — so people concerned about fragrance inhalation might consider applying it lower on the body or on clothing instead.
Weak evidence: Based on where 326-340 already-regular perfume users in one US industry survey said they applied product, not on any measurement of how application site changes inhaled dose.
Source: Loretz 2006, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Measured in people or real products
A typical day's use is about 4 g for facial cleanser, about 14 g (median 10.6 g) for hair conditioner, and about 0.04 g for powder eye shadow, based on a two-week diary-and-weighed-container study of nearly 300 regular US users of each product using their own regular brand.
Weak evidence.
Caveats
Rests on this single 2008 industry study of women-only, US-only, already-regular users of that specific product category; amounts are ratio estimates from total container weight change over two weeks, not measured per application.
Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Self-reported survey
Women with longer, thicker, or curlier hair used noticeably more hair conditioner overall than women with short, fine, or straight hair, while hair oiliness, dryness/damage, and color treatment showed no clear effect on the amount used.
Weak evidence: Rests on this single 2008 industry study's self-reported hair-characteristic categories (box-plot comparison), not a controlled or dose-response analysis.
Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Government agency
Frozen and fatty packaged foods in printed cartonboard (frozen foods, jellies, savory snacks, high-fat items like chocolate) were the categories a UK FSA survey found most likely to carry benzophenone residue from printing-ink migration; fresh or non-printed-packaging foods are a lower-exposure alternative for anyone wanting to reduce incidental dietary intake.
Weak evidence.
Caveats
Based on one national survey's positive-detection rates by food category, not a dose-response health-outcome study Graded weak: what-you-can-do resting on one survey relayed through the IARC monograph.
Source: IARC 2013 Link to this fact
What you can do / Review of other studies
The Endocrine Society recommends that regulatory agencies and civil society organizations support consumer-facing programs like the US EPA's Safer Choice and develop educational materials so consumers can identify and adopt safer product alternatives.
Weak evidence.
Caveats
A general recommendation, not a specific list of safer cosmetic or fragrance alternatives; Safer Choice itself is a voluntary EPA labeling program, not a cosmetics-specific standard.
Source: Endocrine Society 2025 Link to this fact
What you can do / Self-reported survey
If you want to try a pleasant scent at bedtime, this one small study suggests a diffuser-style, indirect delivery may feel more pleasant than a nasal clip or pillow spray (pillow spray was linked to worse self-reported sleep), but don't expect it to change your sleep architecture, and there's no data here on whether it's safe to breathe nightly.
Weak evidence: Rests on one small, non-randomized, industry-funded study with a null objective outcome; not replicated.
Source: Li et al. 2025, Scientific Reports Industry-funded Link to this fact
What you can do / Self-reported survey
People pursuing an MCS accommodation in Canada should ask healthcare providers to document functional limitation, not just a diagnosis, and should keep a written record of every accommodation request and outcome, since the legal duty to accommodate turns on function and this study found requests and refusals were often repeated five or more times.
Weak evidence.
Caveats
Drawn from one self-report survey's qualitative themes and the authors' own policy recommendations, not tested as an intervention; rests on a single small, advocacy-recruited study.
Source: Diallo 2026 Link to this fact
Information, not medical advice. See also: myths we won’t tell you.