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.
Fragrance is everywhere / Measured in people or real products
General-population blood styrene levels (US NHANES, general adult population) run in the range of roughly 0.02-0.2 nanograms per milliliter (50th to 95th percentile across several 1988-2008 survey cycles) — two to three orders of magnitude below levels reported in occupationally exposed reinforced-plastics or rubber workers.
Strong evidence: NHANES biomonitoring data; does not by itself establish health risk at these levels, only relative exposure magnitude versus occupational cohorts.
Source: IARC 2019 (Vol. 121) 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
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
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
All but one author of this fragrance-industry potency review were full-time, fully paid employees of the Research Institute for Fragrance Materials (RIFM) at the time of the work, and the remaining author was paid by RIFM for the time spent preparing the paper — a fully industry-funded and industry-staffed study that sets the potency categories RIFM and IFRA use to justify their own safety limits.
Strong evidence: Disclosed by the authors themselves in the paper's own conflict-of-interest statement.
Source: Na et al. 2022, Dermatitis Industry-funded 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 / Other evidence
A cosmetic product's fragrance-allergen labeling can legally differ between Great Britain and Northern Ireland, because Northern Ireland automatically continues to track EU cosmetics rules under the Windsor Framework (Annex 2's general alignment mechanism for placing manufactured goods on the market) while Great Britain runs its own, separately updated regime.
Strong evidence.
Caveats
Official UK government statutory guidance, updated 29 June 2026, checked directly (accessed 2026-09-28). States the general EU-alignment mechanism for NI, not a specific confirmation that any one EU amendment (such as Regulation 2023/1545) has by name reached NI.
Source: OPSS 2026 (GB/NI guidance) Link to this fact
Laws and loopholes / Other evidence
As of September 2026, Great Britain has not adopted the EU's expanded fragrance-allergen labeling list (Commission Regulation (EU) 2023/1545): the most recent identified GB amendment to the cosmetics regulation's restriction annexes (UK SI 2026/109, made 4 February 2026) addresses unrelated CMR substances, ozone, and a hexyl-salicylate concentration cap, and neither adds to the fragrance-allergen declaration list nor references Regulation 2023/1545, while Northern Ireland continues to track EU cosmetics rules generally under the Windsor Framework.
Strong evidence.
Caveats
Based on this SI's full primary text plus the GB/NI split documented in this batch's other two sources; does not rule out an allergen-list change in one of the five earlier GB cosmetics SIs (2022/659, 2023/836, 2024/455, 2024/1334, 2025/413) named in this SI's own footnote but not independently read here. GB's non-adoption is 'as of' this capture (2026-09-28), not a claim about a permanent decision; industry sources describe an OPSS consultation on alignment as only 'expected.'.
Source: UK SI 2026/109 Link to this fact
Children and pregnancy / Government agency
The European Commission's 2018 endocrine disruptor framework names fetal development and puberty as the exposure periods of greatest concern, stating that exposure during these windows may cause permanent effects and raise disease susceptibility later in life.
Moderate evidence.
Caveats
This restates the 2012 UNEP/WHO consensus report rather than presenting new data of its own; the underlying 'no safe threshold'/non-monotonic dose-response evidence behind that consensus is itself disputed by a later industry-funded critique (see the WHO/UNEP 2012 source page).
Source: EU Commission 2018 Link to this fact
Fragrance is everywhere / Review of other studies
Of 83 chemicals the EPA had flagged as priorities for safety review (TSCA Work Plan), 65 (over 80%) were known to be in consumer products.
Moderate evidence: Not fragrance-specific.
Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact
Fragrance is everywhere / Measured in people or real products
A silicone ingredient in everyday deodorants, lotions, and hair products (D5) shows up in city outdoor air on a clear morning schedule tracking when people shower and dress for work, peaking around 6-7 AM and fading over the following several hours.
Moderate evidence.
Caveats
Diurnal emission-rate profile derived for one mid-sized US city (Boulder, CO, winter 2015/2017); Toronto ground-site data (2009) show a similarly timed morning peak in concentration, but the emission-rate model itself is Boulder-only.
Source: Coggon 2018, Environmental Science & Technology Link to this fact
Green, natural and unscented / Review of other studies
Most 'natural' or herbal deodorant actives described in this review (essential oils such as tea tree and usnic acid, and dozens of herbal extracts) work the same way synthetic actives like triclosan and silver compounds do: by killing or inhibiting the skin bacteria that cause odor, not through some fundamentally gentler mechanism.
Moderate evidence: Based on antibacterial potency (MIC/MBC) data only; this review does not compare skin-irritation or sensitization rates between herbal actives and synthetic anti-microbial salts.
Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact
Green, natural and unscented / Measured in people or real products
Not all fragrance-based odor masking works the same way: Iso E Super, a common deodorant fragrance chemical that barely blocked the malodor receptors in lab dish tests, still reduced how strong a sulfur malodor smelled to people, but less effectively than beta-ionone, suggesting this masking runs mainly through the brain blending two smells together rather than through receptor blocking.
Moderate evidence: Central-processing explanation is the authors' inference from a negative in-vitro result, not directly tested; based on the same single-lab, single-cohort study.
Source: Fukutani et al. 2023, Current Biology Industry-funded Link to this fact
Health effects / Self-reported survey
About 1 in 7 Danish adults (14%) reported fragrance-triggered symptoms at least weekly, and 5% had changed where they shop, how they travel, or how they work because of them.
Moderate evidence: Self-report.
Source: Elberling 2005, Clinical and Experimental Allergy Link to this fact
Health effects / Review of other studies
Cleaning products were the suspected exposure in 236 of 1,915 (12%) confirmed work-related asthma cases across California, Massachusetts, Michigan, and New Jersey (1993-1997); in California, janitors and cleaners had roughly double the confirmed-case rate of all other occupations combined (4.3 vs 2.3 per 100,000 workers).
Moderate evidence.
Caveats
Now traced to its primary source (Rosenman 2003), not a secondary citation. But the underlying surveillance system's own authors say it misses 53-87% of true cases (Michigan capture-recapture) and that up to 37% of confirmed cases in such systems may not be truly work-related (Malo et al., cited by Rosenman); 'cleaning products' is a broad, mostly unspecified chemical category (36% of named agents never identified further than 'cleaning compound'), not fragrance-specific (limonene only 2/300 exposure counts).
Source: Nazaroff & Weschler 2004, Atmospheric Environment Link to this fact
Health effects / Measured in people or real products
In a Toronto clinic for work-related breathing problems, about 1 in 10 referred workers had an irritable larynx (throat) syndrome rather than asthma; perfumes and cleaning agents, bleaches and air fresheners were among the named triggers.
Moderate evidence.
Caveats
Single referral clinic, retrospective, n=30; perfume named by 5/30 and cleaning agents/fresheners by 4/30; 10% of referrals, not of workers. Morrison 1999, the founding case series behind the diagnostic criteria Hoy applied, independently found perfume was a named trigger in only 26% (10/39) of its own ILS cohort, behind reflux (72%) and other airborne irritants (51%) — the syndrome is not fragrance-specific at its point of origin either.
Health effects / Measured in people or real products
About 80% of workers with scent- and irritant-triggered irritable larynx syndrome were women, versus 24–52% of workers with occupational asthma at the same clinic.
Moderate evidence: N=30, one clinic; referral and care-seeking may differ by sex.
Health effects / Measured in people or real products
Over 20 years (1993–2012), California's work-related asthma surveillance confirmed 270 cases linked to perfume or air fresheners at work, 3.8% of all confirmed cases; perfume was the 9th most common workplace asthma exposure.
Moderate evidence: Surveillance count of physician-diagnosed, reported cases; misses >=2/3 of cases; no objective testing required; excludes fragranced cleaners.
Health effects / Measured in people or real products
94% of workers with fragrance-related work asthma in California were women, mostly in offices, health care, and schools, and most cases came from perfume worn by others.
Moderate evidence: Authors attribute the sex skew to occupation and exposure, not susceptibility; care-seeking bias possible.
Health effects / Self-reported survey
Of all personal care product types, perfumes and colognes had the highest hazard ratings in the Environmental Working Group's Skin Deep database, and adults aged 18–39 used the highest-rated ones (average 7.2 of 10, vs 5.9 for those 60 and over).
Moderate evidence: EWG hazard ratings from listed ingredients, not measured toxicity or exposure; 39% of perfumes used could not be rated.
Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Health effects / Review of other studies
A systematic review of workplace irritants found that people with pre-existing airway sensitivity (atopy plus non-specific bronchial hyper-responsiveness) can develop new-onset asthma from chronic, repeated exposure to an irritant at concentrations below the official occupational exposure limit.
Moderate evidence.
Caveats
General occupational-irritant literature (solvents, isocyanates, dusts, gases), not fragrance-specific; the below-OEL pattern is narrative synthesis over 3 older sources plus compiled case-series examples, not an independently SIGN 2+-graded finding.
Source: Baur, Bakehe & Vellguth 2012, Journal of Occupational Medicine and Toxicology Link to this fact
Health effects / Measured in people or real products
Cleaning products were the suspected exposure in 236 of 1,915 (12%) confirmed work-related asthma cases across California, Massachusetts, Michigan, and New Jersey, 1993-1997; most were new-onset asthma (80%) and about a fifth were consistent with reactive airways dysfunction syndrome, an irritant-induced, non-allergic asthma type.
Moderate evidence.
Caveats
This is a primary surveillance source, not a population prevalence estimate: the authors' own capture-recapture analysis found the surveillance system misses 53-87% of true work-related asthma cases in Michigan, and up to 37% of confirmed cases in such systems may not be truly work-related (Malo et al., cited by the authors). Fragrance/limonene was a minor named agent (2 of 300 exposure counts); bleach, acids, disinfectants, and quaternary ammonium compounds dominate.
Source: Rosenman 2003, Journal of Occupational and Environmental Medicine Link to this fact
Health effects / Measured in people or real products
In California, janitors and cleaners had roughly double the confirmed work-related asthma rate of all other occupations combined (4.3 vs 2.3 per 100,000 workers).
Moderate evidence.
Caveats
Single-state comparison using SENSOR case counts against 1990 census occupation denominators; not adjusted for other confounders; occupations with the highest overall work-related-asthma rates (firefighters, correctional officers) were not cleaning-related, so elevated rate alone does not isolate cleaning-product causation.
Source: Rosenman 2003, Journal of Occupational and Environmental Medicine Link to this fact
Health effects / Measured in people or real products
In a 2021 audit of 50 stores across 8 Boston neighborhoods, stores in lower-income Roxbury and Mission Hill were more than twice as likely to stock a hair product with a high (7-10) Environmental Working Group hazard score than stores in higher-income, predominantly White Beacon Hill (risk ratio 2.3 for both).
Moderate evidence.
Caveats
Retail-shelf audit of what stores stock, not what people buy or use; EWG hazard score is a derived ingredient-label rating, not a measured chemical concentration; only 2 of 6 neighborhood comparisons reached statistical significance, and Chinatown was excluded for 94% missing scores.
Source: Chan 2023, Environmental Health Perspectives Link to this fact
Health effects / Measured in people or real products
People with mild asthma performed a concentration task significantly less accurately than healthy people during a 3-hour ozone-limonene chamber exposure, despite working faster.
Moderate evidence: Single study, no unexposed control arm, so it is not established that the chemistry (rather than general chamber occupancy or task load) caused the accuracy difference.
Health effects / Review of other studies
Quaternary ammonium compounds such as benzalkonium chloride (BAC) and didecyldimethylammonium chloride (DDAC) have been linked to occupational asthma, contact dermatitis, and urticaria in healthcare workers, professional cleaners, and hairdressers with heavy, repeated exposure to disinfectants, antiseptics, and cosmetic preservatives.
Moderate evidence.
Caveats
Evidence is case reports, small cohorts, and a few specific-inhalation-challenge studies of occupational/disinfectant/cosmetic exposure, not laundry products; two cited cohort studies of QAC and healthcare-worker asthma directly disagree (see contradictions).
Source: Peyneau 2022, Frontiers in Toxicology Link to this fact
Health effects / Self-reported survey
Among 543 healthcare workers in 7 French hospitals/clinics, occupational exposure to quaternary ammonium compounds (QACs, e.g. benzalkonium chloride) was linked to about 7.5x higher odds of reported physician-diagnosed asthma (adjusted OR 7.56, 95% CI 1.84-31.05) and about 3.2x higher odds of nasal symptoms at work (adjusted OR 3.21, 95% CI 1.42-7.22), after adjustment for age, gender, smoking, BMI, and atopy.
Moderate evidence.
Caveats
Single cross-sectional cohort (not replicated by an independent group); the asthma outcome relies on self-report plus doctor confirmation, not spirometric testing; the confidence interval's lower bound (1.84) shows a wide range of plausible effect sizes; healthy-worker survivor bias could have caused an underestimate, especially among cleaners.
Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact
Health effects / Measured in people or real products
Only 6.5% of tested healthcare workers (32 of 494) had detectable specific IgE antibodies to quaternary ammonium compounds, and this was not significantly associated with reported asthma, new-onset asthma, or nasal symptoms — despite QAC exposure itself being strongly associated with those same outcomes. The study authors read this pattern as pointing to an irritant, not an IgE-mediated allergic, mechanism.
Moderate evidence.
Caveats
Absence of an IgE signal does not rule out a non-IgE immunological mechanism; specific IgE was only tested against a general quaternary ammonium radical, not against every specific QAC compound (e.g. benzalkonium chloride vs. didecyldimethylammonium chloride) separately.
Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact
Health effects / Self-reported survey
Reported physician-diagnosed asthma prevalence varied sharply by healthcare occupation: 16.1% among nurses, 16.7% among auxiliary nurses, 7.7% among cleaners, 5.1% among other healthcare workers, and 3.4% among administrative staff (overall 11.2%, p=0.003).
Moderate evidence.
Caveats
Descriptive prevalence from a single cross-sectional cohort; differences between nurses and cleaners may partly reflect a healthy-worker survivor effect (cleaners with severe asthma more likely to have left the job) rather than only differences in true exposure or risk.
Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact
Health effects / Review of other studies
Benzalkonium chloride (BAK), the preservative in most glaucoma eye drops, accumulates in the trabecular meshwork and other deep ocular tissues after chronic topical use and has a tissue half-life of about 20 hours in the corneal/conjunctival epithelium.
Moderate evidence: Accumulation is well documented; a causal link between that accumulation and disease progression is not established by these detection studies alone.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
Health effects / Other evidence
BAK-exposed trabecular meshwork tissue and cells share the same qualitative cellular and molecular damage signature — cell loss, apoptosis, increased reactive oxygen species, extracellular matrix accumulation, decreased outflow, fibronectin upregulation, and cellular senescence — seen in the trabecular meshwork of primary open-angle glaucoma patients.
Moderate evidence.
Caveats
This shared signature is correlational. The review states explicitly that the causal hypothesis (BAK worsens glaucoma, rather than merely resembling it) is unproven and was, at the time of writing, only beginning to be tested in a nonhuman-primate model. See C324.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
Health effects / Self-reported survey
Weekly use of disinfectant/cleaning sprays at work was associated with worse asthma control in US nurses (OR 1.50, 95% CI 1.16-1.94 for poorly controlled; OR 1.38, 95% CI 1.00-1.92 for very poorly controlled), and the association held even among nurses who used sprays less than once a week.
Moderate evidence.
Caveats
Self-reported spray use; the paper attributes the effect to higher inhalation potential from spray application rather than to a specific chemical, since sprays covered multiple product types (surface, patient care, air-refreshing).
Source: Dumas 2017, European Respiratory Journal Link to this fact
Health effects / Review of other studies
The same authors' own worked example for ammonia — comparing a mouse near-zero-effect threshold (42 ppm) to the human no-effect level, then adding a further factor to account for ordinary variation between people — lands on a combined safety margin of about 4 to 5, not the smaller factor of about 2 that a later 2024 review attributes to this paper for protecting sensitive groups.
Moderate evidence.
Caveats
Single worked example for one chemical (ammonia); the 'about 2' figure the authors separately cite is explicitly for age/sex/lifestyle/disease combined in a general population, not derived fresh in this paper, and not tested against moderate or severe asthma/allergy.
Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Health effects / Lab study (cells or chemistry)
BAK's ocular toxicity is proposed to work partly through mitochondria: because BAK is positively charged and mitochondria are the only negatively charged compartment inside cells, cell studies cited in this review found BAK triggers oxidative stress and can inhibit mitochondrial function by more than 90%.
Moderate evidence: Mechanism drawn from in vitro/cell-culture studies cited by the review, not measured directly in intact human eyes.
Source: Goldstein 2022, Eye Industry-funded Link to this fact
Health effects / Lab study (cells or chemistry)
Exposing primary human bronchial epithelial cells (air-liquid interface culture) to a disinfectant-concentration (0.4%) benzalkonium chloride aerosol for 24 h produced 2,810 differentially expressed genes (1,475 up, 1,335 down), mapping onto DisGeNET disease networks for asthma, COPD, and pulmonary fibrosis; IL1RL1 and IL6R (upregulated) are independently reported as elevated in human asthma patients.
Moderate evidence.
Caveats
Single cell-culture model, one lab, no animal or human validation of the transcriptomic findings; the authors themselves call the existing evidence that BKC causes respiratory disease in humans 'insufficient' and frame this as hypothesis-generating.
Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact
Health effects / Government agency
An international expert working group convened by the World Health Organization and UN Environment Program concluded that close to 800 chemicals are known or suspected to interfere with hormone receptors, hormone synthesis, or hormone conversion, but only a small fraction of them have been tested for whether they actually cause overt endocrine effects in an intact organism.
Moderate evidence.
Caveats
This is a 2012 expert-consensus count covering every kind of suspected endocrine disruptor (industrial chemicals, pesticides, plastics, cosmetic ingredients, natural compounds), not a fragrance-specific count, and the report is now well over a decade old.
Source: WHO/UNEP 2012 Link to this fact
Health effects / Government agency
Benzophenone's oxidative metabolite 4-hydroxybenzophenone, which is estrogenic in vitro (MCF-7 cells, ERalpha binding) and in vivo (rat uterotrophic assay), can also be formed by ultraviolet or sunlight irradiation of benzophenone itself, not only by enzymatic metabolism; the Working Group noted this matters because benzophenone has been used as a UV filter in cosmetics.
Moderate evidence.
Caveats
Photochemical formation and estrogenic activity of the photoproduct are drawn from cited primary studies (Hayashi et al. 2006, Nakagawa & Tayama 2001/2002) summarized in the monograph, not independently re-verified here; this describes the parent compound's own photoproduct, not a sunscreen-derivative UV filter's photoproduct.
Source: IARC 2013 Link to this fact
Hidden ingredients / Self-reported survey
About two-thirds (64.6%) of US adults did not know fragrance ingredients don't have to be listed on the label, and more than half would prefer fragrance-free workplaces (53.2% vs 19.7% against) and health care (54.8% vs 22.4%).
Moderate evidence: Opinion survey.
Source: Steinemann 2016, Air Quality, Atmosphere & Health Link to this fact
Hidden ingredients / Measured in people or real products
Most healthcare workers using disinfectants did not know whether the products they used contained quaternary ammonium compounds: 99 of 543 subjects (18.2%) could not be classified by exposure status from self-report alone, and researchers had to independently review Material Safety Data Sheets with 3 experts to determine actual product ingredients.
Moderate evidence.
Caveats
This describes a French occupational healthcare-worker population in 2006-2007, not consumers; it does not measure how well consumers can identify QACs in household cleaning products from labels today.
Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact
Indoor air / Measured in people or real products
In a real working primary school, mopping a classroom with a limonene-containing detergent produced bursts of tens of thousands of tiny new particles per cubic centimeter within minutes, but only when ozone was present in the air; a plain water-only mop produced no such burst.
Moderate evidence.
Caveats
One school, one detergent; particle number not mass. Classroom mopping peak ~35,000/cm3; matched controlled lecture-theater trials with the same detergent confirmed peaks up to ~68,500/cm3.
Source: Morawska 2009, Environmental Science & Technology Link to this fact
Indoor air / Other evidence
The 25 mg/m3 total-VOC chamber dose that produced a measurable lung-function decline in asthmatics is, in the authors' own framing, a maximal concentration seen in new houses but only a moderate one in the work environment — not a typical existing-home level.
Moderate evidence: This is the paper's own characterization of the dose, not a broad survey of home VOC levels for our cross-paper comparison.
Source: Harving et al. 1991, American Review of Respiratory Disease Link to this fact
The industry / Measured in people or real products
In a French fragrance-and-flavor factory, the company's own measurements found the butter-flavor chemical diacetyl (linked to 'popcorn lung' in US factory workers) in workers' breathing air at 0.05–9 ppm during short tasks; 29 of 31 samples were above the 15-minute limit of 0.1 ppm recommended by the EU's scientific committee on occupational limits.
Moderate evidence.
Caveats
Limit comparison is our (paper makes none); samplers on clothing, respirator use per task not reported; flavor chemical, factory workers, not consumers; industry-funded (V. Mane Fils).
Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact
The industry / Measured in people or real products
The standard EU (REACH) screening tool for estimating workers' chemical exposure predicted lower levels than were actually measured in 61% of 431 measurements in a fragrance-and-flavor factory, sometimes by more than 100-fold.
Moderate evidence: One plant; evidence base count from the paper's S4 table (paper: 37% of tool predictions were above the measurement); short task samples.
Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact
The industry / Industry source
Even after this 2017 update, the fragrance industry's own aggregate exposure model still explicitly excluded household cleaning and laundry products — the product category the industry's own 2003 safety-process paper says accounts for about 60% of fragrance volume — and named their inclusion as future work.
Moderate evidence.
Caveats
Single industry methods paper describing its own model's scope; the gap was closed industry-wide only in a later 2024 paper (Lee et al.), which this claim's caveat should be read alongside.
Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Industry source
To build this exposure model, the fragrance industry combined three surveys that were never designed to work together — a 7-day product diary, a monthly recall survey, and a categorical daily-frequency questionnaire — by matching subjects only on age and gender and assuming they share the same habits for entirely unrelated products.
Moderate evidence.
Caveats
The paper's authors are explicit about this assumption's uncertainty and do not test it directly; a companion validation paper (Safford et al. 2017) is not yet in this evidence base to check how much this integration step affects final exposure estimates.
Source: Comiskey 2017 (RIFM/Creme Global), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Review of other studies
All three named authors of this inhalation-TTC methodology paper were Unilever employees at Unilever's own research center (Colworth Science Park, UK), and the paper states 'The authors declare that there are no conflicts of interest' even though the work was industry research explicitly aimed at reducing inhalation-toxicology testing requirements on the authors' own company's aerosol consumer products under REACH and the EU Cosmetics Directive's 2013 animal-testing ban.
Moderate evidence.
Caveats
A self-declared 'no conflicts of interest' statement from an industry-employed author group performing industry-funded research aimed at reducing regulatory testing burden on their own company's products.
Source: Carthew, Clapp & Gutsell 2009, Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Review of other studies
After a separate 'exception letter' sent in March 2015 by the National Candle Association, the original study's authors deleted a sentence reporting that formaldehyde in three scented-candle types (925, 1022, and 2098 ppb) exceeded workplace TLV (325 ppb) and PEL (730 ppb) limits, and softened a paper highlight from 'exposure levels of some species are high enough to exceed guideline values' to 'can approach or exceed certain guideline values.'
Moderate evidence.
Caveats
This is a documented instance of a trade association prompting language softening and deletion of a specific hazard finding in an academic paper's corrigendum; it does not mean the underlying revised emission-factor numbers (which went up, not down) are wrong.
Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact
The industry / Self-reported survey
The cosmetics industry generated its own dataset for how much lipstick, body lotion, and face cream people actually use, written by staff of the cosmetics trade association (CTFA), the fragrance industry's safety institute (RIFM), a contract statistics firm, and personal-care manufacturers including P&G, Unilever, Avon, Johnson & Johnson, Mary Kay, L'Oreal, Bath & Body Works and Takasago.
Moderate evidence.
Caveats
No funding statement is printed in the paper, but every author's affiliation is a cosmetics/fragrance trade body or personal-care manufacturer; absence of a disclosure is not evidence of independence.
Source: Loretz 2005, Food and Chemical Toxicology Industry-funded Link to this fact
Laws and loopholes / Review of other studies
History shows removing the exposure works: as industrial turpentine use fell from 94.5% of US supply as a solvent in 1935 to 4.5% in 1975, turpentine skin allergy declined with it.
Moderate evidence: Ecological historical correlation.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
Laws and loopholes / Review of other studies
Official limits for the same gas odorant differed about 280-fold in 2009: Germany allowed 50 ppm at work, a Dutch health agency derived 0.18 ppm, and the US had no limit.
Moderate evidence: Regulatory values as reported by the paper (2009); may have been revised since.
Source: Baur & Bittner 2009, American Journal of Industrial Medicine Link to this fact
Laws and loopholes / Measured in people or real products
Workers with fragrance-related asthma were twice as likely as other work-asthma cases to still be exposed at work (50% vs 26%) and more often had workers' compensation claims denied (30% vs 21%), though ER visit and hospitalization rates were the same.
Moderate evidence: Interviewed cases only (~58% of fragrance cases); unadjusted.
Laws and loopholes / Review of other studies
A fragrance-and-flavor company reported that about half of the chemicals it handles are classified hazardous, and that few of the more than 3,000 flavoring substances in use have workplace exposure limits.
Moderate evidence: Industry self-description, no inventory published; flavor materials at one company.
Source: Angelini 2016, PLoS ONE Industry-funded Link to this fact
Laws and loopholes / Review of other studies
A 2015 CMAJ editorial (Flegel & Martin, CMAJ 187:1187, DOI 10.1503/cmaj.151097) states hospital environments free from artificial scents 'should become a uniform policy, promoting the safety of patients, staff and visitors alike'; the US CDC's own workplace policy separately says fragrance 'is not appropriate for a professional work environment' (CDC wording still unverified against a primary CDC source).
Moderate evidence.
Caveats
CMAJ quote now verified against the primary editorial, now in our evidence base (src-2015-artificial-scents-no-place-hospitals): exact wording is 'should become a uniform policy' (ASEQ-EHAQ's paraphrase drops the article 'a', not a substantive misquote). The editorial is opinion/commentary, not a study — its own cited prevalence numbers (30% scent sensitivity, 27% of asthmatics worsened) are the same Caress & Steinemann survey figures used elsewhere in our evidence base. CDC portion remains unverified; the CMAJ editorial itself never mentions the CDC.
Source: ASEQ-EHAQ 2020 (quoting CMAJ 2015 and CDC) Link to this fact
Laws and loopholes / Self-reported survey
MCS is legally recognized as a disability in Canada, but in a national survey most people with MCS who asked for a workplace or housing accommodation before the pandemic (85% of 119) were refused at least once (the paper's own figure: 'at least 78%').
Moderate evidence.
Caveats
Self-reported, cross-sectional, community-based convenience sample of 119 recruited substantially through an MCS advocacy charity's own channels (ASEQ-EHAQ, which also funded the study and paid some authors); over-represents Quebec; likely under-represents the most severely affected.
Source: Diallo 2026 Link to this fact
Skin allergy / Review of other studies
Atopic dermatitis skin has a weakened barrier that allows topical drugs up to about 800 Dalton (tacrolimus 822 Da, the ascomycin derivative SDZ ASM 981 811 Da) to work, whereas the same molecules and larger ones (cyclosporine, 1202 Da) are not effective applied topically to normal skin.
Moderate evidence: Narrative synthesis of separately published clinical trials, not a new experiment; treated by the authors as the named exception to their own 500 Dalton rule.
Source: Bos & Meinardi 2000, Experimental Dermatology Link to this fact
What you can do / Self-reported survey
About twice as many Australians would prefer fragrance-free workplaces (42.8%) as fragranced ones (22.2%), and over three times as many prefer unscented flights (57.7% vs 16.3%).
Moderate evidence.
Source: Steinemann 2017, Preventive Medicine Reports Link to this fact
What you can do / Self-reported survey
Most people would rather have fragrance-free spaces: 65% prefer fragrance-free airplanes, 61% hotels, 51% health care, and 48% workplaces, against 16-22% who prefer them fragranced.
Moderate evidence: Preference survey, adults 18-65.
Source: Steinemann 2019, Air Quality, Atmosphere & Health Link to this fact
What you can do / Self-reported survey
People with asthma back fragrance-free spaces by wide margins: 66.2% vs 16.1% for fragrance-free workplaces and 72.1% vs 14.8% for fragrance-free health care.
Moderate evidence.
Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact
What you can do / Self-reported survey
More UK adults prefer fragrance-free over fragranced workplaces (44.7% vs 23.3%), health care (43.3% vs 26.7%) and airplanes (61.9% vs 18.4%).
Moderate evidence: Pluralities, not majorities, for workplace and health care; preference, not health benefit.
Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact
What you can do / Review of other studies
Occupational lung specialists treating irritable larynx syndrome recommend a 'low-scent' workplace policy or respiratory protection to limit exposure to triggers.
Moderate evidence: Clinical recommendation, not tested as an intervention.
What you can do / Measured in people or real products
The California Department of Public Health recommends enforced fragrance-free workplace policies, no air fresheners or fragranced cleaners, and better ventilation instead of odor masking.
Moderate evidence: Recommendation from a public-health agency based on surveillance, not an intervention trial.
What you can do / Self-reported survey
A fragrance-free sign is not enough on its own: Canadians with chemical sensitivities described workplaces and hospitals with 'scent-free' policies where staff still wore scents and scented cleaners stayed in use.
Moderate evidence: Qualitative focus groups, n=60 self-selected MCS/IAQ-affected Canadians; advocacy-funded.
Source: Roy 2026 Link to this fact
What you can do / Review of other studies
Smell scientists reviewing the evidence found that scenting workplaces to boost mood or productivity is not well supported, and noted that a chemically intolerant employee can react to a fragranced workplace.
Moderate evidence: Short narrative review; the positive-scent literature it weighs is small; no primary data.
Source: Dalton & Jaén 2010, Current Opinion in Allergy and Clinical Immunology Industry-funded Link to this fact
What you can do / Self-reported survey
Support for fragrance-free health care and workplaces is not limited to people with symptoms: in Germany roughly 70% of those who backed them reported no fragrance-related health effects themselves.
Moderate evidence: Our arithmetic from Table 5; preference, not outcome; German workplace support was only 33.2% (30.6% against, 35.3% unsure).
Source: Klaschka 2020, Environmental Sciences Europe Link to this fact
What you can do / Government agency
Workplace accommodations for fragrance sensitivity do not have to be a building-wide ban: the US Labor Department's Job Accommodation Network lists scent-free meeting rooms, moving a worker away from air fresheners and vents, telework, air purifiers, signage, and staff education.
Moderate evidence: List of options, not tested for effectiveness.
What you can do / Measured in people or real products
Being below a standard occupational exposure limit does not mean an irritant gas is safe for someone with asthma: chamber studies found severe asthma attacks from sulfur dioxide and sulfuric acid at concentrations at or below typical workplace limits for those substances.
Moderate evidence: Occupational limits are set for healthy workers by design; this is not itself an argument that the limits are wrong, only that they don't protect people with asthma.
Source: Johansson 2016, Critical Reviews in Toxicology Link to this fact
What you can do / Review of other studies
When relying on a workplace, clinic, or school's fragrance-free policy, check whether it (1) defines what's covered beyond perfume, especially cleaning and laundry products, (2) sets a default fragrance-free expectation rather than a complaint-triggered one, (3) controls what cleaning/laundry products the institution buys, and (4) names a real consequence for non-compliance — a 2026 scoping review of 63 such policies found these structural features present in well under half of cases.
Moderate evidence: Based on a gray-literature document review of North American policies; individual policies may vary, and having these features on paper does not guarantee enforcement.
What you can do / Review of other studies
Aluminum-salt antiperspirants (aluminum chlorohydrate and related salts) work by two combined mechanisms: they physically plug sweat ducts by polymerizing into a gel at skin pH, and they directly inhibit the growth of odor-causing skin bacteria; fragrance is not the active mechanism.
Moderate evidence: Mechanism review synthesizing older primary studies; does not itself measure sweat reduction or bacterial counts in a new trial.
Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact
What you can do / Government agency
EPA's official framework for improving indoor air quality ranks three strategies in order: (1) source control (remove or reduce the pollutant source), (2) increased ventilation, and (3) air cleaners, which EPA says are far more effective for particles than for gaseous pollutants.
Moderate evidence: Agency guidance/assertion, not a controlled comparison of the three strategies.
Source: US EPA, "The Inside Story" Link to this fact
Fragrance is everywhere / Hypothesis
Immigrant women in the US most often work as house cleaners and make up 71% of manicurists; an expert job-exposure tool rates both jobs as probably exposed to fragrance chemicals, and house cleaning also to cleaning-product ingredients such as alkylphenols and antimicrobials.
Weak evidence: Exposure ratings from job descriptions (WORC), not measurements.
Source: Knox 2026, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Health effects / Measured in people or real products
Two German gas-works plumbers who repeatedly hand-poured the gas odorant tetrahydrothiophene in an unventilated room developed chronic rhinitis and lasting airway obstruction; neither had allergies on skin testing, and the accident insurer accepted both as occupational disease.
Weak evidence: Two case reports; exposure estimated, not measured; one worker smoked ~16 pack-years; industrial odorant, not fragrance.
Source: Baur & Bittner 2009, American Journal of Industrial Medicine Link to this fact
Health effects / Review of other studies
A cohort of laborers acutely exposed to gasoline vapors above allowed limits during an underground tunnel-excavation job later developed symptoms similar to those reported in multiple chemical sensitivity, and the study authors argued the workers' sociocultural profile made simple psychosomatic suggestibility an unlikely sole explanation.
Weak evidence.
Caveats
Cited secondhand from Davidoff et al. (primary study not yet in our evidence base); occupational cohort with no independent control for pre-existing chemical sensitivity, and "unlikely to be suggestible" is the original authors' qualitative judgment, not a tested exclusion of a psychological contribution.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Other evidence
In cultured human trabecular meshwork cells, BAK concentrations as low as 0.00002% — well below the 0.005-0.02% range found in commercial glaucoma drops — significantly reduced cell density and cell growth.
Weak evidence.
Caveats
Single in vitro study; bovine trabecular meshwork cells in a different study required about 50x that concentration (0.001%) to show the same effect, so results vary by species and cell state.
Source: Rasmussen et al. 2014, citing Samples et al. 1989, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
Health effects / Lab study (cells or chemistry)
BKC aerosol exposure altered secretion of 166 proteins in bronchial epithelial cells (84 up, 82 down); a gene-disease network of the upregulated secreted proteins linked GDF15, MMP1, and VEGFA (each increased two- to three-fold) to atherosclerosis and cardiovascular disease, suggesting inhaled BKC could have a direct, not just stress-mediated, systemic cardiovascular effect.
Weak evidence.
Caveats
This is a novel hypothesis from one cell-culture secretome analysis cross-referenced against disease-association databases (DisGeNET, CTD), not a measured blood biomarker change in an exposed animal or human; the authors describe it as warranting further investigation.
Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact
Health effects / Other evidence
A screening-level model of a heavy occupational scented-candle exposure (aromatherapy workers, 8 hours a day for 40 years) found a 95th-percentile lifetime lung cancer risk from PAHs alone of 1.20 in a million, marginally exceeding the commonly used 1-in-a-million risk threshold, under the single worst combination of low ventilation and intermediate humidity tested.
Weak evidence.
Caveats
PAH-only estimate (excludes co-emitted benzene, formaldehyde, and particulate matter that would add to total risk); occupational 8h/day/40-year exposure scenario, not typical home candle use; single candle formulation and small chamber; only the 95th-percentile Monte Carlo estimate under the single worst condition exceeded the threshold, not the mean case.
Indoor air / Measured in people or real products
In a week-long study of 7 working adults in Leipzig, the air at home made up 42-73% of the airborne chemicals they breathed, more than the outdoor air or their workplaces.
Weak evidence: N=7, one week, 25 VOCs; home share includes infiltrated outdoor air.
Source: Gokhale 2008, Science of the Total Environment Link to this fact
The industry / Other evidence
This review of BAK's harms to the trabecular meshwork was partly funded by Merck, Inc., and its senior author, Paul Kaufman, discloses paid consultant, honoraria, and financial-support relationships with Alcon and Allergan, both manufacturers of BAK-free alternative eye-drop preservatives (SofZia and Purite respectively) that the review discusses favorably.
Weak evidence.
Caveats
This is a conflict-of-interest disclosure, not an evidentiary finding. The funding pattern runs opposite to a typical 'industry defends its own product' case: the paper argues against a preservative (BAK) while its senior author has financial ties to companies selling competing, BAK-free alternatives.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
What you can do / Self-reported survey
People affected by fragrance say policies work only with purchasing rules for fragrance-free, low-emission products, staff education, better ventilation, and consequences for repeat violations, enforced like smoke-free rules.
Weak evidence: Participants' and authors' proposals; not tested as an intervention.
Source: Roy 2026 Link to this fact
What you can do / Review of other studies
Fragrance-free policies are easier to make work when they start with a needs assessment and an inventory of the cleaning and personal products in use, involve employees in drafting, and agree how violations are handled before launch.
Weak evidence: Lessons from unnamed organizations; no outcome data.
What you can do / Review of other studies
Because people with MCS describe both a fear of asking for accommodations (risking hostility) and a fear of staying silent (risking worsening symptoms), workplaces and services that proactively offer fragrance-free accommodation without requiring the person to ask remove one source of this dilemma.
Weak evidence.
Caveats
Qualitative theme ('suppressing vs expressing needs', 9 findings/5 studies) describing participants' experience, not a tested intervention; no study in this review evaluated an accommodation policy's effect. Downgraded moderate→weak 2026-09-27 (Jev audit): the accommodation recommendation is an inference, not a finding.
Source: Driesen 2020, Journal of Psychosomatic Research Link to this fact
What you can do / Animal study
People who work for hours daily near burning scented candles under high job stress (for example, spa, hospitality, or restaurant staff who tend candle displays), rather than casual home users, are the population most directly addressed by this animal model, and may want to reduce burn time or improve ventilation in that specific occupational setting.
Weak evidence.
Caveats
Based on a single small, unreplicated mouse study using an occupational-intensity exposure chamber; no human occupational data were collected, and the specific candle's composition was not disclosed.
Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact
Information, not medical advice. See also: myths we won’t tell you.