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
In 34 California childcare centers, the chemicals at the highest levels in the air children breathed came from cleaning and personal-care products: a silicone ingredient called D5 (median 51 µg/m³) and the citrus-scent chemical limonene (median 33 µg/m³).
Strong evidence: Single-day samples; upper values capped by calibration (underestimates).
Children and pregnancy / Review of other studies
About half of children's cosmetics in a Danish registry (634 of 1,179, 53.8%) listed perfume or a named fragrance allergen, and a US survey of 533 baby/child personal care products found a closely similar share (255/533, 47.8%; Bonchak 2018); in Danish baby-care products the commonest named allergens were linalool, limonene and benzyl alcohol (the US primary does not report limonene or linalool by name).
Strong evidence.
Caveats
Danish half is primary (Botvid 2023): baby-care products specifically were 38.0% (178/468), the least fragranced category — do not write 'half of baby products' for Denmark. 'Fragranced' there includes products naming only an allergen such as benzyl alcohol (often a preservative). US half is now also primary (Bonchak 2018): 47.8% (255/533) across wipes/diaper care/soap/moisturizer/shampoo/sunscreen — but Bonchak's fragrance count is a ~20-keyword composite that does not report limonene or linalool individually, so the 'top three' allergen list is confirmed only for Denmark. Label counts remain lower bounds.
Source: Sukakul 2024, Acta Dermato-Venereologica Industry-funded Link to this fact
Children and pregnancy / Measured in people or real products
Pregnant women who had used perfume or cologne in the past day had 167% higher urine levels of MEP, the breakdown product of the fragrance solvent diethyl phthalate (DEP), than women who hadn't (177 women, Boston).
Strong evidence.
Caveats
Exposure marker, not health outcome; independently replicated in two further US cohorts with overlapping confidence intervals: Parlett 2013 (2.92x, postpartum, SFF multi-site) and Just 2010 (2.3x, 95% CI 1.6-3.3, pregnant, NYC minority cohort, with a dose-response and a null personal-air DEP association pointing to a dermal exposure route).
Source: Braun 2014, Journal of Exposure Science and Environmental Epidemiology Link to this fact
Children and pregnancy / Measured in people or real products
Synthetic musk fragrance chemicals were found in the breast milk of every one of 39 Massachusetts mothers tested in 2004; the most common, galaxolide (HHCB), was in 97% of them.
Strong evidence: One US state, 2004 samples, n=39; no product-use data; no health outcome.
Source: Reiner 2007, Environmental Science & Technology Link to this fact
Children and pregnancy / Measured in people or real products
Musk scent chemicals used in perfumes, deodorants and detergents turn up in mothers' milk fat; a breastfed baby takes in an estimated ~2 micrograms of galaxolide a day.
Strong evidence.
Caveats
Intake is a model estimate from means of detects; the printed intakes do not reproduce from the stated method. Independently corroborated: Lignell 2008 (N=101, Swedish mothers, single lab) estimated median infant HHCB intake at 1650 ng/day (range 50-6950) using the same milk-intake modeling approach, closely matching this paper's printed 1830 ng/day figure in an unrelated country and cohort.
Source: Reiner 2007, Environmental Science & Technology Link to this fact
Children and pregnancy / Review of other studies
Indoor irritant limits are built on studies of healthy young adults; a 2024 toxicology review found only one controlled irritation study in children (none under age 5) and concluded no evidence-based safety factor for children could be set.
Strong evidence: Absence of data, not evidence of harm; the review lists reasons children could be more or less susceptible (e.g. more stable tear film).
Source: Kleinbeck & Wolkoff 2024, Archives of Toxicology Industry-funded Link to this fact
Children and pregnancy / Measured in people or real products
16.5% of children and adolescents patch tested in 9 population studies had a contact allergy, and in Swedish 16-year-olds fragrance (2.1%) was the second most common allergen after nickel.
Strong evidence: Any allergen, not fragrance only; some adolescent studies read too early and underestimate.
Children and pregnancy / Review of other studies
Children exposed to household chemical/cleaning products before birth or in their first year wheeze more often, now replicated in three independent prospective birth cohorts. In the Canadian CHILD cohort (n=2,022), frequent use in early infancy was linked to higher odds of recurrent wheeze (adjusted OR 1.35) and asthma diagnosis (adjusted OR 1.37) by age 3, but not isolated skin-prick allergy (adjusted OR 1.14, ns) — though wheeze combined with allergy was itself raised (adjusted OR 1.49). In the Czech ELSPAC-CZ cohort (n=3,411), each 1-SD increase in an 18-product household chemical exposure score at 6 months raised the odds of intermediate-onset transient, intermediate-onset persistent and early-onset persistent wheeze phenotypes through age 5 (adjusted OR 1.23-1.36), and those persistent phenotypes carried 5-8x higher odds of doctor-diagnosed asthma at age 7 (pediatrician records, not self-report). In the pooled Spanish INMA cohorts (n=2,292), prenatal (third-trimester) use of cleaning sprays raised the odds of both wheezing (OR 1.37) and lower respiratory tract infection (OR 1.29) in the first year of life, with solvents raising wheezing odds (OR 1.30) and air fresheners raising LRTI odds (OR 1.29); bleach, ammonia and non-spray cleaners showed no association.
Strong evidence.
Caveats
All three cohorts are observational and use self-reported product-use frequency, not measured indoor air chemistry. The 'not atopy' finding remains single-cohort (CHILD only); ELSPAC-CZ's atopic-rash variable is a covariate, not an outcome, and Casas 2013 measured neither atopy nor a physician asthma diagnosis, only maternal-reported LRTI and any-wheezing through 12-18 months, so it neither confirms nor refutes the atopy finding. ELSPAC-CZ's asthma outcome is unusually strong methodologically (pediatrician-diagnosed at school age), but that link runs through the wheeze phenotype rather than directly from exposure to asthma. Casas 2013 is the only cohort with genuinely prenatal (rather than early-postnatal) exposure measurement, which strengthens the prenatal-timing evidence specifically, but its own summed cleaning-product-count score was NOT a significant predictor, unlike CHILD's and ELSPAC-CZ's composite scores — an open methodological tension that means 'more products used' is not yet a uniformly replicated exposure metric across all three cohorts, even though several specific products (sprays consistently, plus solvents and air fresheners) are.
Source: Salonen 2024, Environment International Link to this fact
Children and pregnancy / Review of other studies
The government scientists who first linked lavender and tea tree oils to breast growth in children agree that four case reports cannot prove the oils caused it, and have called for epidemiological studies.
Strong evidence: Correspondence; the same letter also calls ER-agonist exposure 'substantial evidence of causality'.
Source: Ramsey et al. 2020 (JCEM reply), The Journal of Clinical Endocrinology & Metabolism Link to this fact
Children and pregnancy / Review of other studies
A 2018 US EPA systematic review found robust evidence that two common phthalates, DEHP and DBP, are linked to male reproductive harm (lower sperm quality; shorter anogenital distance in baby boys exposed before birth) at everyday exposure levels.
Strong evidence: Associations graded by protocol; DEHP/DBP are mainly plasticizers, not fragrance ingredients; no meta-analysis.
Source: Radke 2018 (US EPA), Environment International Link to this fact
Children and pregnancy / Measured in people or real products
A perfume ('eau de cologne') marketed for babies listed 16 different fragrance allergens, the most of 1,179 children's products in a Danish registry.
Strong evidence: A single product (the maximum), not typical; mean 0.4-1.8 named allergens per product by category; label presence, not dose.
Children and pregnancy / Measured in people or real products
In a national Canadian birth cohort (n=2,022), infants in homes with more frequent use of household cleaning products at 3–4 months of age had higher odds of recurrent wheeze (adjusted OR 1.35 per interquartile increase in use) and of an asthma diagnosis (adjusted OR 1.37) by age 3, but no higher odds of isolated allergic sensitization (skin-prick positivity).
Strong evidence.
Caveats
Observational; the authors explicitly state their results do not prove causation. Recurrent wheeze combined with atopy was itself significantly increased (adjusted OR 1.49), so isolated atopy — not allergic sensitization in general — is what showed no association.
Source: Parks et al. 2020, CMAJ (Canadian Medical Association Journal) Link to this fact
Children and pregnancy / Measured in people or real products
Even products marketed 'fragrance free' for children commonly contain contact allergens: of 52 US pediatric products so labeled in 2013, 42 (80.8%) contained at least one NACDG-tray allergen and 29 (55.8%) contained two or more.
Strong evidence: Label-based; allergens are not broken down by which ones appeared specifically in the 'fragrance free' subgroup beyond the count, and no concentration data exist.
Source: Hamann 2015, Journal of Allergy and Clinical Immunology Link to this fact
Fragrance is everywhere / Measured in people or real products
In the US, everyday chemical products (paints, inks, glues, cleaners, personal care products and pesticides) now release about twice as much air-polluting vapor as cars and trucks: 7.6 vs 3.5 million tonnes in 2012.
Strong evidence: All chemical products, not fragrance specifically; coatings/inks/adhesives are 58%.
Fragrance is everywhere / Measured in people or real products
Even in Perth, a city with very clean outdoor air, limonene and pinene (scent chemicals typical of citrus- and pine-scented cleaners and air fresheners) were found in 80-100% of homes when a sensitive test was used.
Strong evidence: Low concentrations (median ~1.5-2.4 µg/m³); sources not measured; 64 weekday-daytime visits.
Source: Maisey 2013, Atmospheric Environment Link to this fact
Fragrance is everywhere / Measured in people or real products
Americans spend about 69% of their time at home and only 7.6% outdoors, so small indoor sources close to people matter far more than their share of total emissions suggests.
Strong evidence: NHAPS time-activity survey.
Source: Weisel 2002, Environmental Health Perspectives Link to this fact
Fragrance is everywhere / Measured in people or real products
In EPA's large 1980s studies of US homes, limonene, the chemical behind lemon scents, was the airborne chemical with the highest average concentration in people's homes.
Strong evidence: 1980-87 TEAM data; no health risk estimated for limonene.
Source: Wallace 1991, Environmental Health Perspectives Link to this fact
Fragrance is everywhere / Government agency
The US Environmental Protection Agency lists air fresheners, cleaners, disinfectants, aerosol sprays and cosmetics among the household products that release volatile organic compounds, both during use and while stored.
Strong evidence.
Source: US EPA 2026 Link to this fact
Fragrance is everywhere / Measured in people or real products
Scientists can identify which everyday products are polluting a city's outdoor air just by measuring a handful of specific chemical fingerprints: a silicone compound (D5-siloxane) for personal-care products and citrus/pine-scent chemicals (monoterpenes, mostly limonene) for fragranced products, confirmed by mobile-lab measurements across New York City, Pittsburgh, Chicago and Denver.
Strong evidence: Outdoor air only; four US cities, no LA data; tracer status is based on population-density correlation and inventory apportionment, not a direct source test.
Source: Gkatzelis 2021, Environmental Science & Technology Link to this fact
Fragrance is everywhere / Measured in people or real products
In blood tests of 100 healthy young adults in Vienna, the synthetic musk galaxolide was found in 91% of samples and musk xylene in 79%; only 7 of the 100 people had no synthetic musks in their blood at all.
Strong evidence: Cross-sectional, healthy university students in one city; no health outcome measured.
Source: Hutter 2009, Science of the Total Environment Link to this fact
Fragrance is everywhere / Measured in people or real products
Two completely different ways of estimating pollution from chemical products, one based on direct air measurements and one based on how much of each product gets sold and used, agreed with each other to within about a quarter.
Strong evidence: Agreement within 25% for the bulk comparison and within 30% for more than half of individual compounds compared, in Boulder and NYC only.
Source: Gkatzelis 2021b, Environmental Science & Technology Link to this fact
Fragrance is everywhere / Measured in people or real products
Musk fragrance chemicals were found in the breast milk of all 101 Swedish first-time mothers tested; the musk chemical galaxolide (HHCB) was detected in every single sample across a seven-year span (1996-2003).
Strong evidence: One Swedish county, single lab/method, N=101; no infant health outcome measured.
Source: Lignell 2008, Environmental Science & Technology Link to this fact
Green, natural and unscented / Measured in people or real products
'Natural' is no protection: lavender oil's own components form skin allergens when exposed to air.
Strong evidence.
Caveats
Primary is Hagvall 2008 (lab open-flask air exposure, 10-45 weeks): the oil oxidized at the same rate as a synthetic mix of its terpenes; 3.3% linalyl acetate-OOH + 0.48% Lin-OOH at 10 weeks; mouse LLNA EC3 36% fresh -> 4.4% at 45 weeks (weak -> moderate); 4/4 oxidized-linalool-allergic patients reacted to oxidized oil (elicitation only, no fresh-oil control). Real-bottle oxidation rates not measured. Lavender oil ~40% linalool (Klaschka 2016).
Source: Bråred Christensson 2016, Contact Dermatitis Industry-funded Link to this fact
Green, natural and unscented / Review of other studies
Fragrance allergens turn up in "fragrance-free" moisturizers and personal-care products across at least four independent surveys: Scheinman named ten US "fragrance-free" products with fragrance ingredients in 1999 (benzyl alcohol in 5 of 10), dermatologists named nine more major-brand examples containing benzyl alcohol in 2007 (including a baby lotion) — two of Scheinman's own named products (Cetaphil Moisturizing Cream, Moisturel Therapeutic Lotion) reappear on this list — a 2016 survey of best-selling US body moisturizers found 18 of 40 labeled "fragrance free" (45%) listed at least one ingredient dermatologists flag for fragrance-allergic patients, and a 2015 survey of 187 US pediatric personal-care products found that of the 52 labeled "fragrance free," 42 (80.8%) contained at least one contact allergen from the standard NACDG screening tray (55.8% had >=2).
Strong evidence.
Caveats
Four independently compiled surveys (1999, 2007, 2016, 2015) across adult and pediatric products now agree that 'fragrance-free'-labeled products commonly contain contact allergens. Hamann 2015's screening tray is broader than fragrance chemicals alone (also preservatives, surfactants; preservatives were in fact its largest allergen category), so its 80.8% is not a pure fragrance-allergen count like Xu 2017's CAMP cross-reactor tally, but the direction and scale match. Still label-based, not chemical analysis; don't name current products without checking today's labels.
Green, natural and unscented / Review of other studies
In the US, "fragrance free", "unscented" and "free and clear" have no legal definition, so each company picks its own meaning; some "unscented" products contain a masking fragrance added to hide the product's smell.
Strong evidence.
Caveats
Expert review; the legal-definition point is not itself quantified, but the practical consequence now is: Hamann 2015 found 42 of 52 (80.8%) US pediatric products labeled 'fragrance free' contained >=1 NACDG-tray contact allergen, converging with Xu 2017's 45% (18/40) for adult moisturizers (narrower CAMP cross-reactor definition). Two independent, systematically screened surveys across different age populations now confirm the practical failure of the 'fragrance free' label; masking fragrance specifically remains unmeasured (see Scheinman 1999 for the one documented case). Strong because the absence of a legal definition is a regulatory fact. Hamann's 80.8% counts any NACDG allergen (mostly preservatives), not fragrance; use Xu 2017's 45% for fragrance-related allergens.
Green, natural and unscented / Industry source
Even the fragrance industry's safety institute said natural fragrance is not safer: "There is no link between the natural origin of fragrance materials and their safety."
Strong evidence: An opinion with no data in the chapter; it agrees with independent emission tests of 'green' products.
Source: Ford 1994 (RIFM) Industry-funded Link to this fact
Green, natural and unscented / Government agency
Health Canada's current guidance (accessed 2026-09-27) states that a cosmetic labeled 'unscented' or 'fragrance-free' may contain a masking agent added to hide other odors, confirming a 2010 secondhand quote of the same policy word for word.
Strong evidence.
Caveats
Confirmed directly against Health Canada's current (2025-03-17/2026-04-24) guidance and its Cosmetic Regulations s.21.4(3) legal basis; no longer resting on a 2010 secondhand NGO quote alone. Does not measure how often masking actually occurs in Canadian products.
Green, natural and unscented / Measured in people or real products
'Natural' oils get no special protection from air: in lab tests, lavender oil's main scent chemicals oxidized just as fast as a synthetic copy made only of those chemicals, and formed the same allergenic hydroperoxides.
Strong evidence: Lab chemistry, neat oil in open flasks over 10-45 weeks; one oil type (lavender), two batches.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
Green, natural and unscented / Government agency
FDA states that products labeled "unscented" may still contain fragrance ingredients, because a manufacturer may add just enough fragrance to mask the smell of other ingredients without giving the product a noticeable scent.
Strong evidence: FDA gives no formal regulatory definition of "unscented" or "fragrance-free" anywhere on the page; this is the only statement it makes about either term.
Source: FDA 2026 (Fragrances in Cosmetics) Link to this fact
Green, natural and unscented / Government agency
In Canada, a cosmetic labeled 'unscented' or 'fragrance-free' can legally still contain a fragrance ingredient added specifically to mask another smell, declared only as 'parfum' or 'fragrance' on the ingredient list.
Strong evidence.
Caveats
Health Canada's own current guidance (accessed 2026-09-27) and the Cosmetic Regulations s.21.4(3) legal basis; confirms and dates a 2010 secondhand quote of the same policy (David Suzuki Foundation 2010). It does not measure how often masking actually occurs in Canadian products; no Canadian product-testing study of this specific question is in our evidence base.
Source: Health Canada 2026 Link to this fact
Green, natural and unscented / Other evidence
The National Eczema Association's Seal of Acceptance requires products to be fully fragrance-free — "there should be no discernable/strong scent or anything aromatic in nature in the final product" — with no stated exemption for masking fragrance, and NEA directly checks a physical product sample for absence of scent as part of the review.
Strong evidence.
Caveats
This describes NEA's written rule and process, not a chemical measurement of any Seal-holding product; a more detailed 'clinical testing requirements' PDF is referenced but was not captured on this page.
Source: NEA 2026 Link to this fact
Green, natural and unscented / Other evidence
Seal of Acceptance products must also exclude a named 34-ingredient Ecz-clusion List (including cinnamic alcohol, cinnamic aldehyde, coumarin, eugenol, farnesol, geraniol, hydroxycitronellal, isoeugenol, oak moss absolute and several citrus extracts), chemical UV absorbers other than titanium/zinc/iron physical sunscreens, and formaldehyde releasers, in any amount.
Strong evidence: Ingredient-list exclusion, verified by NEA's own review, not independent chemical assay of finished products.
Source: NEA 2026 Link to this fact
Health effects / Animal study
Some older fragrance ingredients were neurotoxic: the nitromusk musk ambrette caused nerve damage in animal studies and was later withdrawn.
Strong evidence.
Caveats
Primary now read directly: Spencer 1984 is a large (N=220), dose-ranging, dual-route (dietary+dermal), histopathologically confirmed (light+EM) study showing clear dose-response demyelination and distal axonal degeneration. Note: musk ambrette's actual withdrawal from skin-contact products was driven primarily by a separate photoallergy finding (Cronin 1984), not directly by this neurotoxicity data, which RIFM had already argued had an adequate safety margin (>600) via absorption data (Ford 1994). Doses producing consistent neurotoxic effects are 50-250x the industry's own estimated maximum human exposure.
Source: Curtis 2004 (citing Spencer 1984), Environmental Health Perspectives Link to this fact
Health effects / Review of other studies
Chamber studies of asthma exclude moderate and severe asthmatics by design, and the one study that directly compared severity bands found the excluded group had the largest airway response — so these studies likely underestimate how sensitive people with asthma really are.
Strong evidence.
Caveats
Confirmed by a separate 103-study systematic review (Johansson 2016), whose own quality criteria excluded moderate/severe asthma in every included study; its one direct severity comparison (Linn et al. 1987, sulfur dioxide) found the moderate/severe group had the largest SRaw/FEV1 impairment, though not statistically significant in that small sample. Direction is now doubly confirmed (two independent reviews built on the same design flaw); magnitude of the underestimate is still not quantified.
Source: Kleinbeck & Wolkoff 2024, Archives of Toxicology Industry-funded Link to this fact
Health effects / Review of other studies
Chamber studies show irritant gases cause severe airway narrowing in people with asthma at concentrations at or below standard workplace exposure limits: asthmatics had severe bronchoconstriction to sulfur dioxide at about 0.4 ppm (1.1 mg/m3) after just 5-10 minutes of exercise, and to sulfuric acid at about 1 mg/m3.
Strong evidence.
Caveats
Quantified by Johansson 2016 (103-study systematic review): asthmatics showed severe airway narrowing (SRaw >=200%, FEV1 drop >=20%) to sulfur dioxide at >=1.1 mg/m3 (~0.4 ppm) after 5-10 min exercise and moderate-severe responses to sulfuric acid around 1 mg/m3 (oronasal) or 0.35 mg/m3 (mouth-only); both sit at or below typical occupational exposure limits for these substances (e.g. ACGIH SO2 TWA ~2 ppm/STEL 5 ppm; background knowledge, verify against current ACGIH tables). This is now primary chamber data, not only a secondary citation of Baur 2012's occupational-asthma review. Still not specific to fragrance chemicals; these are combustion/industrial irritant gases. Strong for sulfur dioxide and sulfuric acid only; no equivalent chamber data exist for fragrance chemicals, so do not transfer the grade to fragrance.
Source: Kleinbeck & Wolkoff 2024, Archives of Toxicology Industry-funded Link to this fact
Health effects / Review of other studies
In the same EPA review, diethyl phthalate (DEP), the phthalate used in fragrance, had only 'slight' evidence of male reproductive effects, the weakest of six phthalates, even though people are exposed to it the most.
Strong evidence: Use to set the record straight, not to accuse fragrance; 'slight' is not 'none' (more high-confidence studies needed).
Source: Radke 2018 (US EPA), Environment International Link to this fact
Health effects / Measured in people or real products
In the largest controlled test of its kind, 130 healthy young women breathing an indoor chemical mixture with and without ozone for 140 minutes showed no significant change in symptoms, lung function, attention or the stress hormone cortisol.
Strong evidence: Healthy women only; asthma and chemical sensitivity excluded; one 140-min exposure at 1.8 air changes/h; eye-blink rate not measured.
Source: Fiedler 2005, Environmental Health Perspectives Link to this fact
Health effects / Measured in people or real products
A systematic review of 103 controlled chamber studies found asthmatics develop severe airway narrowing to sulfur dioxide at concentrations around 1 mg/m3 (about 0.2-0.4 ppm) after just 5-10 minutes of exercise, while healthy people showed no response even at 15 mg/m3; individual dose-response modeling put asthmatics about 9 times more sensitive to sulfur dioxide than healthy people.
Strong evidence: Sulfur dioxide is a combustion/industrial gas, not a fragrance chemical; asthmatic subjects were mild cases only (severe asthma excluded by design).
Source: Johansson 2016, Critical Reviews in Toxicology Link to this fact
Health effects / Measured in people or real products
Every controlled chamber study in a 103-study review of asthma and airborne chemicals excluded people with moderate or severe asthma by design; the one study that directly compared severity groups found the more severe group had the largest airway response, though not statistically significant in that small sample.
Strong evidence: Direction, not magnitude: the comparison (Linn et al. 1987) was underpowered and did not reach significance.
Source: Johansson 2016, Critical Reviews in Toxicology Link to this fact
Health effects / Animal study
Musk ambrette, once a widely used musk fixative in fragrances (over 100,000 lb/year in the US since the 1920s), caused nerve-fiber demyelination and degeneration in a large industry-funded rat study of 220 animals, with hindlimb weakness ranging from isolated cases at moderate doses to complete weakness at the highest dose tested.
Strong evidence.
Caveats
Large (N=220), dose-ranging, dual-route (dietary+dermal) primary with clear dose-response and light+EM histopathology confirmation; doses producing consistent effects are 50-250x the industry's own estimated maximum human exposure.
Source: Spencer 1984, Toxicology and Applied Pharmacology Industry-funded Link to this fact
Health effects / Review of other studies
The cosmetics industry's own expert safety panel states plainly, in its own report, that no data exist — published or industry-submitted — on whether PTFE (Teflon) is absorbed through the skin or how the body distributes, metabolizes or excretes it.
Strong evidence.
Caveats
Absence of data is not evidence of harm; the tested endpoints (acute toxicity, irritation, sensitization, genotoxicity) were negative at cosmetic use concentrations. This narrow claim is about dermal absorption/ADME only — it does not extend to endocrine or environmental effects, which this document does not address at all.
Source: CIR 2018 Industry-funded Link to this fact
Health effects / Measured in people or real products
Most patients with scent- and chemical-triggered breathing symptoms in this study (8 of 12) were already taking asthma inhalers or steroid inhalers and said the drugs gave little or no relief, matching an independent Canadian clinic's finding that a similar scent-triggered condition does not respond to asthma medication.
Strong evidence.
Caveats
Both this and the corroborating study (Hoy 2010) are single-clinic case series (n=12 and n=30); 'little relief' is patient-reported, not measured by a controlled inhaler-response trial.
Hidden ingredients / Measured in people or real products
In lab tests of 213 US household and personal-care products, not one label listed a phthalate, yet the phthalate DEP, a common fragrance solvent, turned up in half of the pooled conventional product samples.
Strong evidence: Products bought 2007-08; composited samples; content not dose.
Source: Dodson 2012, Environmental Health Perspectives Link to this fact
Hidden ingredients / Review of other studies
US law does not require the individual chemicals in a fragrance to be listed, so a shopper cannot tell from the label whether a scented product contains diethyl phthalate.
Strong evidence: Regulatory background statement, as of 2013.
Source: Parlett 2013, Journal of Exposure Science and Environmental Epidemiology Link to this fact
Hidden ingredients / Review of other studies
None of the products used by the four affected children was ever chemically analyzed; the researchers could only assume that a product labeled as containing lavender oil actually met the international composition standard.
Strong evidence.
Caveats
Stated by the authors as a limitation; an industry letter later claimed one named cologne contained diethyl phthalate and no lavender oil, which has also never been independently verified.
Source: Ramsey 2019, The Journal of Clinical Endocrinology & Metabolism Link to this fact
Hidden ingredients / Review of other studies
The industry's own safety panel wrote that a single fragrance can contain 50-300 ingredients, that formulas are 'carefully guarded', and that the industry 'is often perceived as rather less than forthcoming by consumers and their physicians'.
Strong evidence: Direct quotation from an industry-authored 2003 paper; 50-300 is a range, not a measured count.
Source: Bickers 2003 (RIFM Expert Panel), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Hidden ingredients / Advocacy group testing
Ingredient labels cannot show what is inside 'parfum': a 2010 Canadian cosmetics survey had to leave out diethyl phthalate, a common fragrance solvent, because 'short of a laboratory analysis, there's no way to know'.
Strong evidence: Illustrative quote; for measured prevalence cite Dodson 2012 (DEP in 21/42 conventional composites, no label listed a phthalate).
Hidden ingredients / Government agency
US cosmetic labels can still say just "fragrance". The 2022 law requires companies to name fragrance allergens on the label, but only the ones the FDA lists in a regulation, which the law told the FDA to propose by June 2024.
Strong evidence: Statute §609(b); allergens, number and thresholds left to FDA; check whether the final rule is in force before saying labels carry them.
Source: MoCRA 2022 Link to this fact
Hidden ingredients / Government agency
Even the FDA can only ask what is in a cosmetic's fragrance after a serious adverse event it has reason to blame on the fragrance; the company may answer with "categories of ingredients", and the answer is exempt from public-records requests.
Strong evidence: Statute §605(f); 30-day deadline; records access separately excludes formulas (§610).
Source: MoCRA 2022 Link to this fact
Hidden ingredients / Review of other studies
About 1 in 10 (370 of 3,820) topical medicines in a Belgian survey were labeled as containing a fragrance ingredient, and there is no EU or Belgian legislation restricting fragrance in topical medicines.
Strong evidence.
Caveats
Now sourced directly from the primary (Nardelli 2009), not second-hand via Pastor-Nieto 2021; exact figures confirmed (370/3,820 = 9.7%, rounds to the paper's stated 10%). This is a label survey (fragrance listed as an ingredient), not a reaction-rate or chemical-analysis figure; 127 of the clinic's 3,378 iatrogenic-ACD patients (3.8%) had a confirmed reaction to one of the fragranced products. Nardelli 2009's own abstract misprints the product-count denominator as 3,280 — use 3,820 from its Methods/body.
Source: Pastor-Nieto 2021 (Nardelli 2009), Current Treatment Options in Allergy Link to this fact
Hidden ingredients / Review of other studies
Sanitary pads, panty liners and tampons can contain undisclosed fragrance allergens — chiefly alpha-isomethyl ionone (in every scented tampon tested), hexyl cinnamal and benzyl salicylate, plus trace limonene, linalool and geraniol — and in the EU they do not have to declare any of them.
Strong evidence.
Caveats
Primary source (Desmedt 2020, validated HS-GC-MS/FID, 10 scented Belgian AHPs) now in our evidence base. The compounds actually found above the EU 10 ug/g labeling threshold were alpha-isomethyl ionone (all 4 tampons, 12.6-19.1 ug/g), hexyl cinnamal and benzyl salicylate (one panty liner); limonene, linalool and geraniol were all trace (<10 ug/g) — the original claim named the wrong allergens as the notable ones.
Source: Pastor-Nieto 2021 (Desmedt 2020), Current Treatment Options in Allergy Link to this fact
Hidden ingredients / Measured in people or real products
Unlisted PFAS impurities (perfluorocarboxylic acids, including chain lengths that overlap PFOA) were found in nearly every PFAS-containing cosmetic tested in a 2024 study, and these unlisted impurities transferred into artificial sweat far more readily (43-76%) than the PFAS ingredient actually printed on the label (which showed negligible transfer).
Strong evidence.
Caveats
Bioaccessibility (partitioning into artificial sweat) is a precursor to, not proof of, skin absorption; sebum was not included in the assay and may raise this further; small sample; no PTFE-containing products were tested.
Source: Namazkar 2024, Environmental Science: Processes & Impacts Link to this fact
Hidden ingredients / Measured in people or real products
In Belgium, about 1 in 10 topical (skin-applied) pharmaceutical products — wound-healing ointments, NSAID gels, antiseptics, antihemorrhoidals, even corticosteroid-antibiotic creams — listed a fragrance ingredient, sometimes disclosed only as the single word "Perfume".
Strong evidence: 370/3,820 products in a Belgian label survey (2009); a label/composition survey, not chemical analysis; historical product list, not a current market snapshot.
Hidden ingredients / Measured in people or real products
A single undisclosed "Perfume" in one antibiotic-corticosteroid cream (Mycolog/Triadcortyl) caused allergic reactions in 34 patients — more than any other product in a 30-year clinic series — and its 28-ingredient composition was only obtained by directly asking the manufacturer, not from the label.
Strong evidence: Single-clinic case series; one product's undisclosed formula, not a general claim about all perfume-labeled products.
Hidden ingredients / Measured in people or real products
Health Canada's own testing of 252 Canadian cosmetic and personal care products found the fragrance solvent DEP in 70% of fragrance products, at levels up to 2.6% by weight, yet every DEP-positive product was labeled only with the generic term "parfum" — never DEP or any phthalate.
Strong evidence.
Caveats
N=252 individually tested products, Canadian market, 2007-08; detection frequency is lower than two smaller earlier surveys (Hubinger & Havery 2006, EWG 2002) found for fragrances specifically.
Source: Koniecki 2011, Environmental Research Link to this fact
Indoor air / Review of other studies
A chemical released indoors is roughly 1,000 times more likely to be breathed in than the same amount released outdoors (exact when comparing the low end of each range; only ~100x at the high end, since the ranges overlap at 10⁻³), so cleaning products and air fresheners (about 1% of California's smog-forming emissions) may deliver an inhaled dose on the same scale as all outdoor sources combined.
Strong evidence.
Caveats
Modeled population intake fractions (not measurements), population-average estimate. Traced to the primary source, Lai, Thatcher & Nazaroff 2000 (JAWMA 50:1688-1699), which derives outdoor PITF 10⁻⁶-10⁻³ vs indoor/in-vehicle PITF 10⁻³-10⁻¹ from Gaussian-plume and mass-balance modeling (Nazaroff co-author of both papers, so this is not independent replication). The ranges overlap at 10⁻³, so '1000x' is a floor-to-floor comparison, not a fixed multiplier under all conditions.
Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact
Indoor air / Review of other studies
Scent chemicals such as limonene and pine oil react with ozone indoors to make new pollutants, including formaldehyde and fine particles, that keep forming for hours after cleaning ends.
Strong evidence: Size of the effect depends on dose and indoor ozone; confirmed by later chamber and field studies.
Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact
Indoor air / Measured in people or real products
Limonene was detected in every childcare room studied and was more than 1,000 times higher indoors than outdoors, so it came from products used inside.
Strong evidence: Outdoor detected in 1/20 sites.
Indoor air / Measured in people or real products
Questionnaires about habits and routines correctly sorted only 20% of people by their measured exposure to cleaning and fragrance chemicals, vs 61% for traffic fumes; exposure depends on individual behavior and product choice.
Strong evidence.
Caveats
'Product choice' is the authors' explanation, not directly tested in this paper; independently corroborated by a larger, more direct 2021 UK study (Heeley-Hill 2021, 60 homes, daily diary-logged — not recalled — product-use frequency vs measured concentrations) that found cumulative product-use frequency has essentially no predictive power for measured indoor VOC concentrations (R²<0.001 for total VOC; no individual VOC significant).
Source: Edwards 2006, Atmospheric Environment Industry-funded Link to this fact
Indoor air / Review of other studies
Scent chemicals released by perfumes and scented products can react with ozone in indoor air to form new pollutants, including formaldehyde and fine particles.
Strong evidence.
Caveats
Formation is well established (Fiedler 2005: 40 ppb O3 + a limonene/alpha-pinene-containing VOC mix -> HCHO 13 -> 40 µg/m³, UFP 2,500 -> 46,000 cm-3; Singer 2006; Rossignol 2013; Destaillats 2006 gives the underlying per-ozone yield). Amounts depend on dose and ozone; the harm at real indoor levels is not shown. A far more rigorous, independent toxicologist review (Wolkoff & Nielsen 2017) reaches the same qualitative chemistry conclusion via its own literature synthesis and adds a quantitative caution: in the two largest human tests to date (Fiedler 2005, n=130; Fadeyi 2015, n=71), the resulting reaction mixture caused no significant airway/eye effects, and its own threshold estimate is that >200 µg/m³ ozone at high limonene would be needed before sensory effects are expected. Cite primaries for numbers.
Source: Alblooshi 2025, Frontiers in Toxicology Link to this fact
Indoor air / Measured in people or real products
Across decades of US monitoring where people carried personal air samplers, the air they breathed held more of almost every hazardous chemical than outdoor air did: exposure happens indoors, not at the outdoor monitoring station.
Strong evidence: Older studies include smokers' homes; compound-specific.
Source: Weisel 2002, Environmental Health Perspectives Link to this fact
Indoor air / Measured in people or real products
Air fresheners, deodorizers and moth crystals were identified as the household source of p-dichlorobenzene, which reached about 300 µg/m³ indoors while being nearly absent outdoors.
Strong evidence: P-DCB is a deodorizing active, not a fragrance ingredient.
Source: Weisel 2002, Environmental Health Perspectives Link to this fact
Indoor air / Measured in people or real products
Formaldehyde in New Jersey homes averaged about seven times the outdoor level (55 vs 13 parts per billion).
Strong evidence: Regional sample; building materials are a major source alongside products.
Source: Weisel 2002, Environmental Health Perspectives Link to this fact
Indoor air / Measured in people or real products
For p-dichlorobenzene, an often unlabeled deodorizer in air fresheners and moth repellents, 97% of people's exposure came from sources inside the home, not outdoor air.
Strong evidence: Deodorizer/pesticide active, not a fragrance ingredient.
Source: Wallace 1991, Environmental Health Perspectives Link to this fact
Indoor air / Measured in people or real products
In week-long air measurements across 11 European cities, the scent chemicals limonene and alpha-pinene were the compounds most concentrated in homes compared with workplaces (about 4x), attributed to perfumes, cleaning and fragranced products.
Strong evidence: Source attribution by the authors, not measured per product.
Source: Geiss 2011, Atmospheric Environment Link to this fact
Indoor air / Measured in people or real products
Limonene was 13x higher indoors than outdoors in European offices and classrooms, one of the two highest indoor/outdoor ratios of 23 chemicals measured.
Strong evidence: Ratio of medians.
Source: Geiss 2011, Atmospheric Environment Link to this fact
Indoor air / Measured in people or real products
Most European homes had low limonene (median 9.5 ug/m3 over a week), but the heaviest-use homes reached weekly averages up to 493 ug/m3, the range used in lab studies of indoor ozone chemistry.
Strong evidence: Upper tail only; median home 20-60x below chamber levels.
Source: Geiss 2011, Atmospheric Environment Link to this fact
Indoor air / Measured in people or real products
In a real test house, using a limonene-scented foam cleaner exactly as the label directed produced a burst of 45,000-150,000 tiny new particles per cubic centimeter within minutes, but only when ozone was in the air.
Strong evidence.
Caveats
One product, one house; particle number not mass. Independently replicated in a second real building (a working primary school; Morawska 2009), with a different detergent and country, at a similar order of magnitude (5.89-6.85×10^4 cm-3 in controlled tests) and the same water-only-no-burst, ozone-dependent pattern.
Source: Rossignol 2013, Atmospheric Environment Link to this fact
Indoor air / Measured in people or real products
Scent-type chemicals typical of fragranced and cleaning products (limonene, pinene, carene) were the signature of home air: close to zero outdoors but tens to hundreds of times higher inside homes.
Strong evidence.
Caveats
Small original study (n=7); the indoor-source signature (not the specific product-category attribution) is now independently replicated by a much larger 2021 UK study with real paired outdoor sampling (Heeley-Hill 2021, 60 homes: limonene indoor:outdoor ~19x, alpha-pinene ~10x), though that larger study also found cumulative product-use frequency does not predict concentration (only insecticide/plug-in-air-freshener use showed weak covariance with limonene) — so the indoor-source signature is strong, the specific 'cleaning products' attribution stays inferential. Givaudan-funded (COI); analysis independent.
Source: Gokhale 2008, Science of the Total Environment Link to this fact
Indoor air / Lab study (cells or chemistry)
What you breathe after using a scented cleaner is not only what was in the bottle: the scent chemicals keep reacting in the air to make new compounds.
Strong evidence: Well-established chemistry; magnitude indoors depends on ozone levels.
Indoor air / Review of other studies
Scented cleaners react with ozone indoors and release bursts of tiny new particles; every study able to separate them found this.
Strong evidence.
Caveats
Particle number, not mass; magnitude depends on instrument size cutoff and dose. Now confirmed across chamber, real test-house, real-office and real-classroom settings (Rossignol 2013, Rosales 2022, Wu 2024, Morawska 2009).
Source: Salonen 2024, Environment International Link to this fact
Indoor air / Measured in people or real products
In a controlled chamber, the people themselves were the main thing reacting with indoor ozone: four seated adults removed about 60–65% of it, in two separate campaigns with men and with women, and their skin oils turned it into carbonyls such as 4-oxopentanal and 6-MHO. The same DTU chamber's protocol paper independently reproduced the ~60–69% removal in three more groups — teenagers and seniors as well as adults — across 26 experiments, and showed the sink is dermal (a breath-only control lost almost no ozone).
Strong evidence.
Caveats
Same DTU 22.5 m³ chamber and fan setup in all campaigns (Wang 2024: 4 men, ~37 ppb; Zannoni 2021: 2 groups of 2 women + 2 men, ~35 ppb; Bekö 2020: 5 groups — 3 adult, teenagers, seniors — same chamber/fans, ~35 ppb); mixing fans put deposition velocities at the top of the literature range, and a furnished home also loses ozone to surfaces, so the occupant share there will be lower. Chemistry only, no health endpoint; ICHEAR 6-MHO values may be inflated by an inlet artifact.
Source: Wang 2024, Environmental Science & Technology Link to this fact
Indoor air / Measured in people or real products
Four people in a clean, well-ventilated test room removed about two-thirds of the ozone coming in, confirmed in a second campaign that included women as well as men.
Strong evidence: Same DTU chamber as Wang 2024; ~65% is evidence base arithmetic from a ~100 ppb target inlet; furnished homes also lose ozone to surfaces.
Source: Zannoni 2021, Environmental Science & Technology Link to this fact
Indoor air / Measured in people or real products
When scent chemicals from a pine-oil cleaner, an orange-oil degreaser and a plug-in air freshener met ozone in a lab chamber, about one formaldehyde molecule formed for every 3-5 ozone molecules they used up (yields of 20-30% in most tests).
Strong evidence.
Caveats
Same three products as Singer 2006, same research group/CARB contract, not independent replication; the highest single value (90%) occurred at air-freshener vapor loads 30-45x a real room's plug-in levels.
Source: Destaillats 2006, Environmental Science & Technology Link to this fact
Indoor air / Measured in people or real products
The moment ozone was added to pine-oil, citrus and air-freshener scent vapors in a lab chamber, a burst of new ultrafine particles formed immediately and grew within minutes into fine particles, reaching hundreds of micrograms per cubic meter.
Strong evidence.
Caveats
Bench chamber at cleaning-pulse-scale vapor loads; ultrafine particles were only 1-4% of the mass at steady state, not the 4-16% the paper itself mislabels as an 'ultrafine' yield (that figure is total particle mass, all sizes).
Source: Destaillats 2006, Environmental Science & Technology Link to this fact
Indoor air / Measured in people or real products
In a controlled test room, people removed roughly 60–69% of the indoor ozone in every one of five very different groups tested — teenagers, young adults and people in their 70s alike — showing this is a general property of occupied rooms with ozone present, not a quirk of one age group.
Strong evidence: Chamber study (22.5 m³, DTU, mixing fans push ozone deposition to the top of the literature range), fragrance-free hygiene products only, no health outcome measured.
The industry / Lab study (cells or chemistry)
The lab tests that replaced animal testing for setting cosmetic and fragrance allergy safety limits explain only about 62% of how strongly a chemical causes allergy.
Strong evidence.
Caveats
Regression R2 against mouse LLNA, not human outcomes; industry-authored. Natsch 2023 (same author) retrains against human-anchored data: the 62% figure survives on a blended human+LLNA composite (63.4%, n=139), but against strictly human data (n=62) accuracy drops to 32-45%, and even the LLNA itself only reaches 43% predicting human potency — so '62%' should not be read as human-relevant accuracy. Api, Basketter & Lalko 2014 (RIFM's own earlier LLNA-vs-human validation, 57 fragrance chemicals) independently corroborates, by a different metric (categorical concordance, not R2) and seven years earlier, that the LLNA itself is an imperfect human proxy: 76% agreement within half an order of magnitude, but up to ~790-fold mispredicted for salicylates and ~26-42-fold for trans-2-hexenal/methyl-2-nonanoate. Roberts & Api 2018 (same fragrance dataset, direct LLNA-vs-human regression) reports a much higher R2=0.784, but only for a 35-chemical subset that already excludes those 14 known outliers a priori — demonstrating that domain-restricted R2 figures like this one can substantially overstate accuracy on unselected chemistry, a caution that applies to curated NAM training/case-study sets generally, not only to this specific figure.
Source: Natsch & Gerberick 2022, ALTEX Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
Accuracy has not improved: a 2015 model predicted allergy potency about as well as the 2022 one.
Strong evidence.
Caveats
Confirmed by reading the 2015 primary directly, not just inferred from one comparison line in the 2022 paper: Natsch 2015 Equation 7 gives R²(adj)=62.3% (Results, not the abstract's rounded 60%), matching 2022's 62% and 2023's 59-65%.
Source: Natsch & Gerberick 2022, ALTEX Industry-funded Link to this fact
The industry / Review of other studies
The cosmetics industry's own safety panel judged PGME 'safe' only for nail products and calculated only skin absorption; it did not estimate how much users or nail-salon workers breathe in, and relied on the smell to limit inhalation.
Strong evidence: Verdict probably right for occasional home users; the weakness is in the reasoning, not a demonstrated harm.
Source: CIR 2008, International Journal of Toxicology Industry-funded Link to this fact
The industry / Review of other studies
The Cosmetic Ingredient Review is funded by the cosmetics industry trade association, and the use data, exposure survey and safety-margin calculation behind its 2008 PGME verdict were unpublished industry submissions.
Strong evidence: Much of the underlying toxicology is peer-reviewed; industry funding does not by itself make the conclusion wrong.
Source: CIR 2008, International Journal of Toxicology Industry-funded Link to this fact
The industry / Review of other studies
The fragrance industry's own standard caps this one ingredient at 0.003% in lip products and 0.02-0.05% in typical leave-on skin products – about 30 parts per million in the strictest category.
Strong evidence: IFRA Standards are voluntary; the limits apply to rose ketones individually or in combination.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Review of other studies
For this fragrance ingredient there was no data at all on absorption, repeat-dose toxicity, developmental effects, genetic damage or cancer – the whole safety file is skin testing, and 8 of its 11 studies are unpublished company reports that outsiders cannot check.
Strong evidence: As of the 2006 literature search; later RIFM re-evaluations may have added data.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Review of other studies
Much of the evidence behind the fragrance industry's 'safe as used' verdict on salicylates is unpublished: about 65 of the cited studies are internal RIFM reports, several submitted by fragrance companies, and no modern cancer bioassay exists for any of the 17 chemicals.
Strong evidence: Counted from the paper's reference list; 'no modern bioassay' means untested, not shown to be carcinogenic.
Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Self-reported survey
The study most often cited to call lavender and tea tree oils 'safe' for children was part-funded by the Australian Tea Tree Industry Association, the Tisserand Institute and an aromatherapy association, while declaring no conflicts of interest.
Strong evidence: Funding is documented in the paper itself; funders are stated to have had no role. The paper's weakness is its power and design, not only its funding.
Source: Hawkins 2021, International Journal of Pediatrics and Adolescent Medicine Industry-funded Link to this fact
The industry / Review of other studies
The tea tree oil industry's trade association (ATTIA) challenged the lavender/tea tree case reports in a medical journal, and the same association later helped fund a survey that called the oils safe for children.
Strong evidence: Documents who argued what; says nothing about whether the oils cause breast growth.
Source: Ramsey et al. 2020 (JCEM reply); Hawkins et al. 2021, The Journal of Clinical Endocrinology & Metabolism Link to this fact
The industry / Animal study
The two molecules that give lavender oil its scent, linalool and linalyl acetate, were put through the full regulatory endocrine test battery (OECD guideline cell assays plus rat uterotrophic, Hershberger and one-generation reproductive studies) and came back negative on estrogen and androgen endpoints — in a study written, run and entirely funded by BASF, the company that manufactures both chemicals, with all five authors BASF employees.
Strong evidence.
Caveats
Guideline designs with working positive controls, so the negative is real; the conflict of interest is disclosed in the paper and should be stated whenever the result is cited. Scope: two constituents, not lavender or tea tree oil.
Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact
The industry / Animal study
Nothing in the industry's endocrine testing program covers tea tree oil, whose main constituent, terpinen-4-ol, was never tested.
Strong evidence: A statement about the study's scope, not about tea tree oil's safety either way.
Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact
The industry / Review of other studies
The fragrance industry's safety system is self-run: by its own 2003 description, companies fund the Research Institute for Fragrance Materials through dues, its expert panel reviews ingredient safety, and conclusions go to the industry's trade body IFRA, which sets voluntary standards for those same companies. No regulator appears in the loop.
Strong evidence: Industry's own description (2003); panel members are required to be independent of the industry; later governance changes not covered.
Source: Bickers 2003 (RIFM Expert Panel), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Review of other studies
By the industry's own figures, about 60% of fragrance goes into soaps, fabric softeners, cleaners and detergents, yet its 2003 method for estimating people's exposure counted only 10 personal-care products applied to skin, and breathing fragrance in was not part of the calculation.
Strong evidence: Describes the 2003 process; later RIFM aggregate-exposure work may differ. Shows the route was not assessed, not that it causes harm.
Source: Bickers 2003 (RIFM Expert Panel), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Other evidence
By 1994 the fragrance industry itself had banned or restricted 82 fragrance materials, most because they cause skin allergy and a dozen because they cause skin reactions in sunlight.
Strong evidence: Counts restrictions, not harm rates; limits not printed.
Source: Ford 1994 (RIFM) Industry-funded Link to this fact
The industry / Government agency
In 2000 the EU's scientific advisers recommended banning 36 fragrance materials from cosmetics, and the list they endorsed was the fragrance industry's own list of materials it had already prohibited (IFRA); the committee added no testing of its own and deferred all industry restrictions to later.
Strong evidence: Describes the 2000 procedure; later EU opinions (SCCS 2012) did independent hazard classification.
Source: SCCNFP 2000 Link to this fact
The industry / Review of other studies
A trade consortium of 11 French essential-oil companies funded and employed the authors of the journal letter disputing the lavender breast-growth case reports; together with the tea tree oil trade association's letter, the published rebuttals to those case reports came from industry.
Strong evidence: Documents who argued what (disclosed in the letter); says nothing about whether the oils cause breast growth.
Source: Giroux & Orjubin 2020 (JCEM letter; Consortium Huiles Essentielles), The Journal of Clinical Endocrinology & Metabolism Industry-funded Link to this fact
The industry / Review of other studies
In 1997 the cosmetics industry's own safety panel (CIR) formally asked for inhalation-toxicity data on benzyl alcohol, benzoic acid and sodium benzoate, received none, and still published a 2001 "safe" conclusion that explicitly excludes any product where inhalation is a route of exposure (colognes, hairsprays, deodorants, aerosol fixatives).
Strong evidence: The gap is documented in the report's own text (Notice of Insufficient Data, no comments received); no later CIR report closing it was found in this pass.
Source: Nair 2001 (CIR Expert Panel), International Journal of Toxicology Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
The lab tests that replaced animal testing for fragrance and cosmetic allergy limits have been stuck at explaining about 62% of allergy potency since 2015 — the 2015 model and the 2022 model perform the same.
Strong evidence: Regression R2(adj) against mouse LLNA potency, not human outcomes; industry-funded (Givaudan).
Source: Natsch 2015, Toxicological Sciences Industry-funded Link to this fact
The industry / Measured in people or real products
The independent dermatologists who ran this study concluded deodorants should contain cinnamal at less than 0.01% to protect people already sensitized, a stricter limit than the fragrance industry's later 0.05% IFRA standard.
Strong evidence: Authors' own recommendation, not a regulatory outcome; the 0.05% IFRA cap was set afterward using the induction NOEL, not this elicitation data.
Source: Bruze et al. 2003, Journal of the American Academy of Dermatology Link to this fact
The industry / Review of other studies
The fragrance industry's own risk-assessment methodology (QRA1, then QRA2) has set enforceable safety limits for fragrance materials since 2008, but by its own authors' admission has never been tested against real-world clinical outcomes.
Strong evidence: Industry-authored methodology paper; the paper itself calls for the longitudinal clinical studies that would settle this, and states they have not been done.
Source: Api 2020 (RIFM/IFRA), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Review of other studies
The industry's fragrance safety-limit system (QRA/IFRA Standards) is explicitly designed to prevent new fragrance allergies from developing, not to protect people who are already allergic from reacting to a compliant product.
Strong evidence.
Caveats
Confirmed as the framework's own stated design intent (Section 2.2), not inferred from a single ingredient's numbers; does not itself test whether existing limits provoke reactions in sensitized people.
Source: Api 2020 (RIFM/IFRA), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Government agency
A population study widely treated in dermatology literature as independent, EU-style evidence that confirmed dermatologists' fragrance-allergy estimates over the industry's own claims was itself funded by the fragrance industry's own research body, the Research Institute for Fragrance Materials (RIFM) — a funding fact omitted by every earlier secondhand citation of this study.
Strong evidence.
Caveats
The industry-funded study still confirmed the higher, consumer-relevant estimate (1.9% clinically relevant, up from a disputed 'up to 2%') over industry's own 2000 'far lower' claim — the funding did not appear to weaken the result in this case.
Source: Diepgen 2015 (EDEN), British Journal of Dermatology Industry-funded Link to this fact
The industry / Government agency
The EU guidance that defines what 'free from' and 'hypoallergenic' cosmetic claims are allowed to mean was jointly agreed by the European Commission, all EU/EFTA member states, the main EU cosmetics trade body (Cosmetics Europe) and the fragrance industry's own trade association (IFRA).
Strong evidence: Stated on the document's own cover page (footnote 1); this describes who wrote the guidance, not an independent audit of its content.
Source: EC Technical Document on Cosmetic Claims 2017 Industry-funded Link to this fact
Laws and loopholes / Review of other studies
As of 2008, no US federal law required companies to list all the chemicals in a consumer product or in its fragrance; air fresheners and laundry products did not even have to say they contained fragrance.
Strong evidence.
Caveats
US law as of 2008; MoCRA (2022) later required FDA-designated fragrance-allergen labeling for cosmetics only (rule pending at enactment); household products still uncovered for cosmetics.
Source: Steinemann 2009, Environmental Impact Assessment Review Link to this fact
Laws and loopholes / Review of other studies
This non-disclosure was legal: US law doesn't require household products to list ingredients, and lets 'fragrance' stand in for a whole undisclosed mixture.
Strong evidence: Regulatory analysis as of 2010 (pre-MoCRA).
Source: Steinemann 2011, Environmental Impact Assessment Review Link to this fact
Laws and loopholes / Review of other studies
When US EPA scientists built a database of chemicals in 8,921 consumer products from their safety data sheets, they could not record fragrance ingredients at all: more than 3,060 fragrance materials can legally be listed as 'trade secret' with no name, so those entries had to be thrown out.
Strong evidence: Document analysis of one US retailer's MSDSs (2012).
Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact
Laws and loopholes / Review of other studies
Product safety data sheets are written for workers, not shoppers, and only have to list hazardous ingredients present above 1% (0.1% for cancer-causing ones), a level most individual fragrance chemicals fall below.
Strong evidence: 'Most fragrance chemicals below 1%' is general formulation knowledge, not measured in this paper.
Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact
Laws and loopholes / Review of other studies
A 2023 EU rule expands the list of fragrance allergens that must be named on cosmetic labels from 26 to about 80 entries (56 substances plus related forms), phasing in from 2026 to 2028, above set concentration limits.
Strong evidence: Only above threshold concentrations; cosmetics only.
Source: Sukakul 2024, Acta Dermato-Venereologica Industry-funded Link to this fact
Laws and loopholes / Review of other studies
Since the 2022 MoCRA law, most cosmetic makers must list their products with the FDA; in its December 2025 report the FDA found PFAS ("forever chemicals") intentionally added to about 0.4% of listed US cosmetics (1,744 of 430,134), mostly eye and face makeup, and had too little data to judge the safety of 19 of the 25 most-used PFAS.
Strong evidence.
Caveats
Manufacturer listings, not product testing; small businesses and drug-cosmetics do not list; corrected 2026-09-26 from 0.03%/no fragrances (EU KEMI figures). Independently corroborated 2026-09-27: Balan et al. 2024 (10.1021/acs.est.3c06539, California DTSC) estimated PFAS-containing-product prevalence from a different, non-federal dataset (Mintel Global New Product Database + EWG Skin Deep, ~65,000+ formulations) and found prevalence under 3% in every one of 16 product subcategories studied (range 0.00-2.68%), consistent with FDA's 0.41% aggregate figure. Both remain database/listing-based estimates, not chemical measurements, and the two studies measure slightly different things (an economy-wide aggregate vs. per-subcategory prevalence in 16 categories), so this is convergence of two independent large datasets rather than a replication of the identical statistic.
Source: FDA 2025, FDA report published under MoCRA §3506(b) (FDA website) Link to this fact
Laws and loopholes / Review of other studies
In the US, "fragrance" can be listed as a single word because the mixture is protected as a trade secret, so the individual chemicals are rarely named on the label.
Strong evidence.
Source: Pinkas 2017, Environmental Research Link to this fact
Laws and loopholes / Government agency
There are no federally enforceable US standards for volatile organic compounds in homes, schools or other non-industrial indoor settings.
Strong evidence.
Source: US EPA 2026 Link to this fact
Laws and loopholes / Review of other studies
Linalool and linalyl acetate are registered in the EU at over 1,000 tonnes a year each for fragrance use in home-care and air-care products; the study states its purpose as adding to the dataset for future hazard-classification decisions as the EU adds endocrine disruption to its classification rules.
Strong evidence: Registration tonnage and regulatory context as stated by the paper; dossier-building and scientific inquiry are not separable here.
Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact
Laws and loopholes / Review of other studies
The US Microbead-Free Waters Act (2015) bans plastic microbeads only in rinse-off cosmetics, not in makeup that stays on the skin.
Strong evidence: Statement of US law as summarized in the review.
Laws and loopholes / Review of other studies
Because PTFE is a polymer, the EU's REACH law never required companies to register it or submit safety data, and a planned change to cover polymers was postponed.
Strong evidence: Describes EU law only; the EU universal PFAS restriction proposal may change this.
Source: Jomaa 2024, Journal of the Netherlands Society of Toxicology (JNST) Industry-funded Link to this fact
Laws and loopholes / Industry source
In 1994 a scientist at the fragrance industry's own research institute wrote that no country required fragrance ingredients to be approved, safety-tested for consumer use, or listed on product labels, and called this "of great benefit to the industry".
Strong evidence: Describes 1994; EU labeling of 26 (now more) allergens and US MoCRA came later.
Source: Ford 1994 (RIFM) Industry-funded Link to this fact
Laws and loopholes / Government agency
In 2000, EU cosmetics could declare an entire fragrance as the single word 'parfum'; the EU committee noted dermatologists' estimate that up to 2% of people have perfume allergy, against industry's claim that the true figure was 'far lower'. The EDEN population-based patch-test study (Diepgen 2015; n=3,119 patch-tested across 5 European countries) directly confirmed the dermatologists' estimate: 1.9% (95% CI 1.5-2.5) clinically relevant fragrance contact allergy, and 1.8-2.6% for fragrance mix I alone.
Strong evidence.
Caveats
EDEN is the largest general-population patch-test study of fragrance allergy to date and a large, well-controlled multi-country primary (not a single-lab or single-cohort study), which is why this moves to strong. Note EDEN was itself funded by the Research Institute for Fragrance Materials (RIFM), the fragrance industry's own body — the industry-funded study still confirmed the higher, consumer-relevant estimate over the industry's own 'far lower' claim.
Source: SCCNFP 2000 Link to this fact
Laws and loopholes / Government agency
Since the 2022 Modernization of Cosmetics Regulation Act, cosmetic companies must send the FDA any report they receive of a serious reaction to their product, including serious and persistent rashes, within 15 business days, and the FDA can now order a recall.
Strong evidence: Statute text (FFDCA §§604-605, 611); 'serious' threshold excludes most transient reactions; enforcement from 2023-12-29.
Source: MoCRA 2022 Link to this fact
Laws and loopholes / Government agency
US cosmetics still need no FDA approval before sale: the company itself must keep records showing the product is safe, and the law says "minor and transient reactions" do not make a product unsafe.
Strong evidence: Statute §608; substantiation judged by 'qualified experts', no required tests, no inhalation requirement.
Source: MoCRA 2022 Link to this fact
Laws and loopholes / Government agency
The 2022 US cosmetics law does not cover air fresheners, cleaning products or laundry products at all.
Strong evidence: MoCRA amends the FFDCA cosmetics chapter only; household products fall under CPSC/EPA law.
Source: MoCRA 2022 Link to this fact
Laws and loopholes / Government agency
Until 2023 EU labels only had to name 26 fragrance allergens (above 10 ppm in leave-on and 100 ppm in rinse-off products); every other fragrance ingredient could be hidden under 'parfum'.
Strong evidence: EU Regulation 2023/1545 expanded the list; say 'until 2023' or name the new list.
Source: Pastor-Nieto 2021, Current Treatment Options in Allergy Link to this fact
Laws and loopholes / Review of other studies
In the EU, chemical mixtures containing a skin sensitizer must carry the warning 'May produce an allergic reaction' (EUH208), but cosmetics are exempt from that warning and from CLP hazard symbols.
Strong evidence: Legal analysis as of 2016 (CLP Art. 1(5), Annex II 2.8); cosmetics do have to name listed allergens in the ingredient list.
Source: Klaschka 2016, Environmental Sciences Europe Link to this fact
Laws and loopholes / Government agency
In the EU, tampons and pads are not cosmetics: as of 2020 only general product-safety law applied, so manufacturers could add fragrance allergens without restriction or labeling, signaling scent only with words like "fresh".
Strong evidence: Legal status as of 2020 (GPSD 2001/95/EC, since replaced by GPSR 2023/988); no product-level exposure data.
Laws and loopholes / Measured in people or real products
The US FDA has no directive at all regulating the use of the word 'hypoallergenic' on a cosmetic product, and in a 2015 survey the products so labeled had the highest contact-allergen rate (88.2%) of any of four marketing terms tested (hypoallergenic, dermatologist recommended, fragrance free, paraben free).
Strong evidence: The regulatory point (no FDA directive) is a stated fact, not itself a measured statistic; the 88.2% figure is from a single-region convenience sample of 135 products.
Source: Hamann 2015, Journal of Allergy and Clinical Immunology Link to this fact
Laws and loopholes / Measured in people or real products
No EU or Belgian law requires fragrance ingredients in topical medicines to be named on the label, or restricts which fragrance chemicals they may contain — unlike cosmetics, where the EU has required disclosure of major fragrance allergens since 2005.
Strong evidence: Regulatory statement as described in a 2009 paper; check current EU medicines regulation for any changes since.
Laws and loopholes / Government agency
A systematic comparison of occupational exposure limits from 18 countries and agencies found that only 25 of 1,341 chemicals studied have a limit set by every agency, and more than a third of the chemicals are regulated by only one of the 18.
Strong evidence: Workplace limits only, not consumer or indoor-air limits. A single (if large and systematic) comparative study; the paper does not analyze why the differences exist.
Source: Schenk et al. 2008, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Laws and loopholes / Government agency
In the EU and UK, any cosmetic claim – including 'fragrance-free,' 'unscented,' 'free from X' or 'hypoallergenic' – is legally required to meet six common criteria (legal compliance, truthfulness, evidential support, honesty, fairness and informed decision-making) and must be backed by evidence the company holds on file, under a binding, directly applicable EU regulation in force since 2013.
Strong evidence.
Caveats
The regulation sets these six generic criteria but does not itself specify what evidence threshold applies to any particular claim wording; that level of detail sits in separate, unacquired Commission and industry guidance.
Source: Commission Regulation (EU) No 655/2013 Link to this fact
Laws and loopholes / Government agency
The EU regulation that governs cosmetic claims deliberately declines to define the terms 'free from,' 'hypoallergenic,' 'fragrance-free,' or 'unscented' – it states outright that the common criteria are not meant to define or specify permitted or forbidden claim wording, leaving that to case-by-case enforcement and separate guidance.
Strong evidence: Read from the regulation's own Recital 7 and confirmed by the absence of any of these terms anywhere in its text.
Source: Commission Regulation (EU) No 655/2013 Link to this fact
Laws and loopholes / Government agency
Under US regulations, fragrance and flavor ingredients in a cosmetic can be listed simply as "Fragrance" or "Flavor" on the label, because the Fair Packaging and Labeling Act cannot be used to force a company to disclose trade secrets, and fragrance/flavor formulas are the cosmetic components FDA itself identifies as most likely to qualify.
Strong evidence.
Caveats
This is the legal rule itself, quoted from FDA's own page (captured 2026-09-27); it says nothing about how many or which chemicals this hides in practice (see Steinemann/Dodson/Goldsmith measurements for that).
Source: FDA 2026 (Fragrances in Cosmetics) Link to this fact
Laws and loopholes / Government agency
FDA names laundry detergents, fabric softeners, dryer sheets, and room and carpet fresheners as fragranced products that fall under the Consumer Product Safety Commission rather than FDA cosmetics regulation.
Strong evidence: Statement of jurisdiction only; says nothing about what CPSC does or does not require of these products.
Source: FDA 2026 (Fragrances in Cosmetics) Link to this fact
Laws and loopholes / Government agency
Starting April 12, 2026, Canadian cosmetics must individually name 24 specific fragrance allergens (expanding to 81 by August 2026 for new products and August 2028 for existing products) when present above 0.001% in leave-on products or 0.01% in rinse-off products — a named, dated, threshold-based mandate the parallel US MoCRA fragrance-allergen provision (FFDCA section 609(b)) still lacks.
Strong evidence.
Caveats
The allergen list and thresholds are incorporated by reference from the EU's Annex III list, so Canada's implementation tracks the EU rather than being independently derived; it covers only named allergens, not the rest of any fragrance mixture. The MoCRA comparison is based on the statute's own text (no confirmed final rule as of this evidence base's last check) and FDA's own current consumer page, which as of the same 2026-09-27 capture date states FDA lacks cosmetic allergen-labeling authority and does not mention MoCRA at all.
Source: Health Canada 2026 Link to this fact
Laws and loopholes / Government agency
Canada requires cosmetic fragrance ingredients to be declared as 'parfum' (the word 'fragrance' alone is not acceptable), but does not require disclosure of the fragrance mixture's non-allergen constituents.
Strong evidence: A labeling-word requirement, not a composition disclosure requirement; a full fragrance ingredient list is legally optional, not mandatory, in Canada.
Source: Health Canada 2026 Link to this fact
Laws and loopholes / Other evidence
NEA enters into a paid, annually renewed license agreement with a brand/manufacturer to allow use of the Seal logo once a product is accepted; renewal depends on the manufacturer's own attestation that the formula has not changed, and any formula change requires restarting the application with new clinical testing.
Strong evidence: No fee amount is disclosed on this page; ongoing compliance between renewals relies on manufacturer self-report, not NEA-initiated re-testing.
Source: NEA 2026 Link to this fact
Skin allergy / Review of other studies
EU scientific advisers (SCCS 2012) list 82 fragrance ingredients as established causes of skin allergy in people.
Strong evidence: Cite SCCS 2012 directly; this review is low reliability.
Source: Kumar 2020 (SCCS 2012), Journal of Cosmetic Dermatology Link to this fact
Skin allergy / Measured in people or real products
In 658 Danish/Swedish patients with hand eczema, 67 (10.2%) reacted to fragrance chemicals commonly found in household products, and the standard fragrance-mix patch test alone would have missed more than half of these reactions.
Strong evidence.
Caveats
Clinic-referred hand-eczema population, not the general public. Confirmed directly against the full primary (Heydorn et al. 2003, Contact Dermatitis 48:317-323), not just its PubMed abstract or Kumar 2020's secondary table.
Source: Kumar 2020 (Heydorn 2003), Journal of Cosmetic Dermatology Link to this fact
Skin allergy / Measured in people or real products
The fragrance chemicals most often found in household products were mostly not in the standard fragrance-allergy patch test used at the time: 6 of its 8 chemicals were in 12% of products or fewer.
Strong evidence.
Caveats
Frequency in products is not the same as clinical sensitization rate; FM II and hydroperoxide testing later added. Clinically confirmed in Heydorn et al. 2003 (n=658 hand-eczema patients, 3 centers): only 3 of the 14 chemicals selected from this paper's household-product survey were FM I constituents, and FM I caught only 45.5% of the fragrance-allergic patients (5.6% of all patients tested missed). The exposure-frequency leader, limonene (78% of products), caused only 0.8-0.9% oxidized-limonene reactivity clinically — product frequency of a chemical still does not predict its clinical allergy rate.
Source: Rastogi 2001, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Common scent chemicals such as linalool hardly cause allergy when fresh, but once exposed to air they form new chemicals that do: in 1,511 dermatitis patients at six European clinics, 1.3% were allergic to air-oxidized linalool (later studies with a stronger test found about 7%).
Strong evidence.
Caveats
Dermatitis patients, not general population; 2005 test concentration (2.0% pet.) was later shown too low. Clinical relevance no longer just inferred: Andersch Björkman 2014 (ROAT) shows patients identified this way go on to develop dermatitis from twice-daily use of a cream/perfume containing oxidized linalool at concentrations as low as 0.3% (0.056% linalool hydroperoxides, ~27 µg/cm²) — inside the 0.1–2% range measured for individual fragrance ingredients in real products.
Skin allergy / Animal study
Common fragrance chemicals such as limonene (citrus) and linalool (lavender) react with air to form far stronger skin allergens; in mouse tests, oxidized limonene was about 10 times more potent than fresh limonene.
Strong evidence: Mouse LLNA potency; review of replicated data.
Skin allergy / Measured in people or real products
In European skin clinics, 2.8-5.2% of patients tested for dermatitis reacted to oxidized limonene.
Strong evidence: Consecutive dermatitis patients, not general population.
Skin allergy / Review of other studies
About 1 in 22 European adults (4.5%) tested positive to at least one of six fragrance-related patch-test markers (2008-2011); single fragrance markers pick up 1-3%, and up to 16% of patients referred for patch testing react.
Strong evidence: The 4.5% is a six-marker union including non-fragrance markers (colophonium, sesquiterpene lactones), with no clinical-relevance criterion.
Source: Sukakul 2024, Acta Dermato-Venereologica Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In patch tests of 2,900 dermatitis patients in six countries, 5.2% were allergic to oxidized limonene and 6.9% to oxidized linalool, two of the most common fragrance chemicals.
Strong evidence: Clinic population, not general public.
Source: Bråred Christensson 2016, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Fresh limonene and linalool rarely cause allergy (0.1-0.3% of patients); the allergens form when these chemicals react with air, which also happens in essential oils and perfumes during storage.
Strong evidence: Parent-compound rates cited from IVDK/Danish data.
Source: Bråred Christensson 2016, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In 2,900 dermatitis patients tested at nine clinics in Europe, Asia and Australia, 6.9% were allergic to air-oxidized linalool, the form a common floral scent chemical found in most perfumes, cosmetics and many cleaners takes after contact with air.
Strong evidence: Dermatitis patients, not general population; 72% weak reactions; range 3-14% by clinic.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
60.5% of patients allergic to oxidized linalool would never have learned they had a fragrance allergy from the standard fragrance patch tests.
Strong evidence: Dermatitis patients.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
80% of patients allergic to oxidized linalool whose products were checked were using fragranced products, mainly shampoos, soaps and creams.
Strong evidence.
Caveats
Linalool confirmed in their products in 38%; clinical relevance established in 41%. Andersch Björkman 2014 (ROAT), drawn from this same 2,900-patient cohort's Gothenburg patients, causally confirms the exposure-effect link: repeated open application of oxidized-linalool-containing cream/perfume at real-product concentrations (down to 0.3%) reproduced dermatitis, and participants who had already avoided linalool-containing products mostly reported improvement.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Review of other studies
Limonene and linalool become skin allergens when they react with air: in European dermatitis clinics, 3.9-20% of patients tested reacted to oxidized linalool and 1.4-13.7% to oxidized limonene, against under 1% for the fresh chemicals.
Strong evidence: Clinic patients referred for patch testing, not general population.
Skin allergy / Review of other studies
Standard allergy tests with fresh limonene and linalool miss most of these allergies, so European experts now recommend adding the oxidized forms to routine patch testing.
Strong evidence.
Skin allergy / Measured in people or real products
Among 5,773 people tested for eczema at a Swedish hospital, 9.4% were allergic to the air-oxidized forms of two of the most widely used scent chemicals: linalool (7.0%) and limonene (5.1%).
Strong evidence: Clinic population referred for suspected contact allergy; single center.
Skin allergy / Review of other studies
Scent chemicals such as limonene and linalool rarely cause skin allergy when fresh, but once exposed to air they turn into much stronger allergens; the older the product, the more of them it contains.
Strong evidence: Review of experimental and clinical work; no new data.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
Even the fragrance industry's own safety institute classes the cinnamon-scent chemicals cinnamal and cinnamyl alcohol as human skin sensitizers: in its volunteer tests, 29 of 451 people became allergic to cinnamal at 1% or more.
Strong evidence: Industry-run HRIPT/maximization panels, mostly unpublished RIFM reports; 0/≈200 sensitized at ≤0.5%.
Source: RIFM Expert Panel 2005, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In people already allergic to cinnamal, a deodorant with just 0.01% of it triggered a reaction in 1 of 9, and 0.032% in 4 of 9; the industry limit is 0.05%, and it was set to prevent new allergies, not reactions in people already sensitized.
Strong evidence.
Caveats
Confirmed by the primary source, now in our evidence base: Bruze et al. 2003, an independent (non-industry, no COI declared), double-blind provocation study with a 20-patient non-allergic control group (0/20 reacted) and P<.001 statistics tying the reaction to both cinnamal-sensitization and the actively-scented axilla. The study's own authors recommend a deodorant limit below 0.01%, stricter than the 0.05% IFRA cap.
Source: RIFM Expert Panel 2005 (citing Bruze 2003), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
The fragrance industry's own safety review of the rose ketone cis-beta-damascone records that 10 of 50 human volunteers became sensitized when it was patch tested at 5%, and that the test had to be stopped early because of the number of skin reactions.
Strong evidence: 5% is roughly 100x a fine-fragrance use level (max reported 0.02%); at 0.05% two panels gave 0/53 and 0/28.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Rose ketones are a real but uncommon allergen: 0.5% of 1606 consecutive European patch-test patients reacted to a 0.2% damascone mixture, and none of 202 Japanese dermatitis patients reacted at 2%.
Strong evidence: Clinic populations, elicitation prevalence not induction risk; original data are Frosch 2002 and Kozuka 1996, reported via the RIFM review.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
About 1 in 5 people in the general population (20.1% of 20,107 people patch tested in 28 studies) are allergic to at least one common chemical that touches the skin, such as nickel, fragrance, preservatives or hair dye.
Strong evidence: Meta-analysis, very high heterogeneity (I2 97%); mostly nickel; publication bias detected.
Skin allergy / Measured in people or real products
After nickel, the standard fragrance allergy test (Fragrance Mix I) was the most common positive in the general population: about 3.5% reacted, across 19 studies and 19,440 people.
Strong evidence: Pooled 1966-2017 (CI 2.1-5.4%); the largest modern study found 1.8-2.6% for the same test.
Skin allergy / Review of other studies
The standard fragrance patch test covers only 8 of the 82 fragrance chemicals known to cause allergy in people, so any single test undercounts fragrance allergy.
Strong evidence: Authors' discussion; oxidized limonene/linalool never tested in a general-population sample.
Skin allergy / Measured in people or real products
Among about 4,100 North American patients referred for allergy patch testing in 2019–2020, 12.8% reacted to the standard fragrance mix and 11.1% to oxidized linalool, both among the ten most common skin allergens and both up from 2017–2018.
Strong evidence: Referral population, not the general public; primary is DeKoven 2023 (NACDG), cited by the review.
Skin allergy / Review of other studies
Common fragrance ingredients such as limonene and geraniol turn into stronger skin allergens when they react with air in an opened bottle.
Strong evidence: Review relay only; the numbers come from the primary autoxidation studies on the transformation-products hub.
Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact
Skin allergy / Measured in people or real products
The industry's safety panel cleared linalool, a lavender-scented chemical in most fragranced products, as raising 'no safety concerns' after testing the fresh chemical; independent clinics later found that air-exposed (oxidized) linalool causes allergic reactions in about 7% of patients patch-tested for skin allergy (2,900 patients in 9 centers; 5,773 in Sweden, with rates rising).
Strong evidence: Clinic rates are in dermatitis patients, not the general population; test preparations debated; fresh linalool is genuinely a weak sensitizer.
Source: Bickers 2003 (RIFM Expert Panel), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Skin allergy / Industry source
The industry once allowed the allergen citral only if mixed with a companion terpene (originally tested at about 20% d-limonene, later mandated at ≥25%), claiming the terpene 'quenched' the allergic reaction; the original 1976 evidence for this was a single unreplicated human test with no subject numbers reported and was already internally inconsistent, later industry HRIPTs could not reproduce quenching for a related aldehyde (cinnamaldehyde), and air-oxidized limonene, the proposed quencher, is itself now one of the commonest fragrance allergens (about 5% of patients tested).
Strong evidence.
Caveats
The failed replication documented in our evidence base is for cinnamaldehyde + eugenol/limonene, not citral + limonene itself; IFRA's formal withdrawal of the quenching rule is not documented in our evidence base. The founding 1976 test (Opdyke) also showed the effect failing at a different ratio of the same ingredients (cinnamic aldehyde:eugenol 2.5:1 sensitized where 1:1 had not), and its own essential-oil control (cinnamon bark oil) itself sensitized, contradicting the paper's own summary.
Source: Ford 1994 (RIFM) Industry-funded Link to this fact
Skin allergy / Animal study
Many fragrance chemicals become stronger skin allergens after the bottle is opened: limonene, linalool and geraniol react with air at room temperature to form hydroperoxides that, in mouse tests, sensitize at 5-10 times lower concentrations than the fresh chemical.
Strong evidence: Potency from mouse LLNA; cite Karlberg 2013 as primary; clinic data (Bråred Christensson, Sukakul) confirm oxidized forms are common human allergens.
Source: Pastor-Nieto 2021 (Karlberg 2013), Current Treatment Options in Allergy Link to this fact
Skin allergy / Lab study (cells or chemistry)
Chemicals that only become allergens after they are changed by air or by the skin's own enzymes are the worst-predicted group in the industry's own analysis (4.5- to 6.5-fold error, versus about 2-fold for directly reactive chemicals), because the dish assays cannot oxidize or metabolize anything.
Strong evidence: N=32 chemicals in the worst domain; TIMES-software-assigned mechanistic class, not exhaustively confirmed in vivo.
Source: Natsch 2015, Toxicological Sciences Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In a double-blind study, deodorants containing as little as 0.01% cinnamic aldehyde (cinnamal) triggered allergic skin reactions within weeks in people already allergic to it, while an identical unscented deodorant on the other armpit, and the same deodorants used by 20 non-allergic people, caused no reactions.
Strong evidence.
Caveats
Small cohort (9 sensitized test patients, double-blind arm), but statistically significant (P<.001) with a concurrent negative control group and randomized/blinded contralateral-axilla design.
Source: Bruze et al. 2003, Journal of the American Academy of Dermatology Link to this fact
Skin allergy / Measured in people or real products
For people already allergic to oxidized linalool (the air-exposed form of a common floral fragrance chemical), using a scented cream or perfume containing it at concentrations similar to real products (as low as 0.3% oxidized linalool, 0.056% linalool hydroperoxides) was enough to trigger eczema within three weeks of twice-daily use in a repeated-use trial.
Strong evidence.
Caveats
Small N (6 completers); participants were pre-selected as already patch-test-positive, not a general-population sample; lowest concentration tested (0.1% in perfume) did not produce a formal positive.
Source: Andersch Björkman 2014, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
A positive patch test for oxidized linalool is not just a lab artifact: patients who test positive also develop real dermatitis from everyday-strength fragranced products used the way a consumer would use them, not only from the strong test doses used in the clinic.
Strong evidence: No irritant reactions occurred in vehicle controls, so the effect is allergic rather than irritant; the reverse case (a general population screen) was not tested here.
Source: Andersch Björkman 2014, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
In a controlled study, everyone already allergic to limonene hydroperoxides (11/11) developed a skin reaction within about a week of daily exposure to fine-fragrance-level doses of oxidized limonene (140 ppm and up); healthy people (0/17) had no reaction even at the highest dose tested.
Strong evidence: Single multicenter study; 11 allergic subjects and 17 controls.
Skin allergy / Measured in people or real products
In a 2015 survey of 187 US pediatric personal-care products marketed as hypoallergenic, dermatologist-recommended, fragrance-free or paraben-free, 89% (167/187) contained at least one contact allergen from the standard NACDG screening tray, with a mean of 2.4 allergens per product.
Strong evidence.
Caveats
Single-metro US convenience sample (six unnamed Redlands, CA retailers, 2013), label-based (no chemical verification, no concentrations), and allergen matching by an unaudited custom algorithm; the four marketing-term categories overlap (a product can carry more than one), so subgroup percentages are not independent comparisons.
Source: Hamann 2015, Journal of Allergy and Clinical Immunology Link to this fact
Skin allergy / Measured in people or real products
In a patch test of 3,119 people randomly sampled from the general population of five European countries, 2.6% tested positive to fragrance mix I and 1.9% to fragrance mix II, and 1.9% had a fragrance allergy judged clinically relevant (skin symptoms plus product avoidance).
Strong evidence.
Caveats
The largest, best-controlled general-population fragrance patch-test study to date (n=3,119 of 12,377 interviewed, harmonized protocol across 5 countries); the raw marker-positive rate is higher (4.1%) before the clinical-relevance filter, and about half of marker-positive people do not meet the stricter definition.
Source: Diepgen 2015 (EDEN), British Journal of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In a clinical study of 658 hand-eczema patients across 3 European centers, 67 (10.2%) reacted on patch testing to at least one fragrance chemical selected because it is common in household cleaning and personal-care products used on the hands.
Strong evidence: Clinic-referred hand-eczema population (3 tertiary centers), not a random sample of the general public.
Source: Heydorn 2003, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
More than half (54.5%) of the hand-eczema patients allergic to household-product fragrance chemicals would not have been identified by the standard Fragrance Mix I patch test alone.
Strong evidence: Applies to this hand-eczema clinic population and this specific 14-chemical panel; FM II (2008) and hydroperoxide testing have since narrowed but not closed the gap.
Source: Heydorn 2003, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Review of other studies
Oxidized forms of limonene and linalool, formed when these common fragrance terpenes react with air, are now treated as a standard, distinct fragrance-allergen category in mainstream dermatology, alongside fragrance mix I/II and balsam of Peru.
Strong evidence.
Caveats
This 2025 general-ACD review reflects consensus classification, not new prevalence data; primary prevalence numbers should be cited from Sukakul 2022, Bråred Christensson 2016/2012, or the EECDRG review already in our evidence base, not this source.
Source: Aristizabal-Torres 2025, JAAD Reviews Link to this fact
What you can do / Review of other studies
Never mix bleach with ammonia or acidic cleaners: 13 published poisoning reports, including one death, came from mixing products.
Strong evidence: Case reports; not fragrance-related.
Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact
What you can do / Review of other studies
Choosing fragrance-free personal care products is a reasonable way to cut DEP exposure, since DEP is used as a fragrance solvent; label reading alone will not catch phthalates.
Strong evidence: Reasoned advice; not tested as an intervention in this paper.
Source: Crinnion 2010, Alternative Medicine Review Link to this fact
What you can do / Measured in people or real products
If you have unexplained or recurring dermatitis, ask whether patch testing will include oxidized linalool (and oxidized limonene); standard fragrance tests missed 60% of these allergies.
Strong evidence: Hydroperoxide tests now recommended for baseline series in Europe.
Source: Christensson 2012, Contact Dermatitis Link to this fact
What you can do / Review of other studies
Never mix bleach with ammonia or acidic cleaners: it makes toxic chloramine or chlorine gas.
Strong evidence: Established chemistry; review restates it.
Source: Salonen 2024, Environment International Link to this fact
What you can do / Measured in people or real products
Choosing fragrance-free cosmetic and personal care products is an effective way to cut DEP exposure, since fragrance is consistently the most DEP-dense product category across three independent national surveys and DEP is never named on a label when present via fragrance.
Strong evidence: Based on product-content measurement across three independent surveys (Hubinger & Havery 2006, Dodson 2012, Koniecki 2011), not a tested behavioral intervention.
Source: Koniecki 2011, Environmental Research Link to this fact
Information, not medical advice. See also: myths we won’t tell you.