Don’t take our word for it. Here’s every fact on this site, with its evidence grade, its caveats, and a link to the source, so you can check us.
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.
Health effects / Other evidence
After excluding men with any other chemical or heavy-metal exposure, the BPA associations stayed and grew in Li 2010 (erection not usually possible aOR 10.6, 4.0-28.0).
Weak evidence: Smaller groups (67 exposed); the rise is unexplained and not discussed; one cohort.
Health effects / Other evidence
A friend with MCS says the difficulty of separating the condition from housing barriers is that, with safe housing and accommodation, people "would choose to continue living," and that people may seek MAiD when years of attempts to improve conditions fail.
Weak evidence: Opinion of one person; no data; says nothing about any specific individual's reasons.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Health effects / Other evidence
The pump-blocking lasted at least 24 hours after a 2-hour musk exposure in mussel gill tissue, and the authors raise the possibility that low-toxicity chemicals like musks could make other pollutants more harmful.
Weak evidence.
Caveats
Mechanism hypothesis from one ex-vivo mussel study; co-toxicant uptake was not tested in this paper; human relevance is untested and the authors estimate human body burdens are 1-2 orders of magnitude below the effective concentrations.
Source: Luckenbach 2005, Environmental Health Perspectives Link to this fact
Health effects / Other evidence
Mild thyroid hormone shortage in early pregnancy is a human-cohort-supported risk marker for child ADHD-type symptoms, which makes thyroid disruption a plausible, but so far untested, route for chemicals; this study measured no chemicals.
Weak evidence: Plausibility only; the one formal test of thyroid mediation of a chemical (DEHP) and ADHD was null (Engel 2018), and no fragrance-related chemical was tested.
Source: Modesto 2015 (Generation R), JAMA Pediatrics Link to this fact
Health effects / Measured in people or real products
Because only one urine sample was taken per mother, exposure to short-lived chemicals like BPA is probably underestimated, so true associations in such cohorts could be larger or smaller than reported; the authors' correction raised one BPA odds ratio from 1.4 to 5.4.
Weak evidence: Correction uses borrowed intraclass correlations and assumes classical error; not an observed effect size.
Source: Philippat 2017, Environmental Health Perspectives Link to this fact
Health effects / Measured in people or real products
Among 43 urinary chemicals, only one single-chemical result survived false-discovery-rate correction: higher triclosan went with lower inattention scores (count ratio 0.89, 95% CI 0.83 to 0.96), the opposite direction to what a harm hypothesis predicts.
Weak evidence.
Caveats
Cross-sectional, one cohort, unexplained direction; the DEHP and MNBP single-chemical associations did not survive correction; rat work points the other way and the two are not directly comparable.
Source: Oh 2024 (CHARGE), Environmental Health Link to this fact
Health effects / Measured in people or real products
In the same children, many chemicals (BPA, ethyl-paraben, MEHP, oh-MiNP, oxo-MiNP, methyl-paraben and some pesticide metabolites) went with higher urinary cortisol, cortisone and corticosterone production, with BPA largest (about 0.26 to 0.29 on the log scale).
Weak evidence.
Caveats
Cross-sectional; hormones from the night urine and chemicals from a different pooled sample; no multiplicity correction; mechanism (e.g. 11-beta-HSD2 inhibition) is from in-vitro work cited by the authors.
Source: Fabbri 2025 (HELIX), Environmental Research Link to this fact
Health effects / Review of other studies
A 2026 narrative review proposes that chemically different endocrine disruptors (bisphenols, phthalates, PCBs, pesticides, flame retardants, some metals) converge on shared brain mechanisms for learning and memory: calcium signaling, glutamate and GABA signaling, oxidative stress, epigenetic changes and glial inflammation.
Weak evidence: Narrative review with no grading or pooling; nearly all supporting mechanism data are rodent and cell-culture studies, not human.
Source: Jocsak 2026, Frontiers in Behavioral Neuroscience Link to this fact
Health effects / Other evidence
In boys only, the pregnancy chemical mixture was associated with higher internalizing (anxiety/depression-type) scores, 3.59 points per quartile (95% CI 0.42 to 6.75), but the sex interaction was not significant (p about 0.69) and nothing was corrected for multiple comparisons.
Weak evidence: Subgroup estimate; weights driven by PCB180, DEHP metabolites and methyl paraben; not a fragrance finding.
Source: Puvvula 2026, Environ Int, Environment International Link to this fact
Health effects / Other evidence
In the Atlanta survey, 30.2% of the people who called themselves chemically sensitive also reported asthma, against 12.1% of the whole sample.
Weak evidence: Descriptive cross-tabulation only: the brief prints no asthma rate for the non-sensitive group and tests no association; self-reported asthma.
Source: Caress & Steinemann 2004 (AJPH), American Journal of Public Health Link to this fact
Health effects / Other evidence
Among Atlanta adults who reported being chemically sensitive or unsure, about 3 in 10 (29.9%) said it made shopping in stores difficult and 13.5% said they had lost a job because of it.
Weak evidence: Self-report; asked of 'yes' plus 'not sure' respondents, not only the 199 'yes'; causation of job loss not verified.
Source: Caress & Steinemann 2004 (AJPH), American Journal of Public Health Link to this fact
Health effects / Other evidence
Atlanta (12.6%) and California (15.9%) used the same chemical-sensitivity question; the authors call the two 'statistically similar' without printing a test, though a simple two-proportion check (wiki arithmetic, unweighted) puts the 3.3-point gap at about z = 3.3.
Weak evidence: Unweighted check; the California survey was weighted and the Atlanta brief reports no weighting or design effect, so the real gap test is uncertain.
Source: Caress & Steinemann 2004 (AJPH), American Journal of Public Health Link to this fact
Health effects / Other evidence
In this five-country survey 34.6% of adults scored as highly chemically intolerant (25% in Mexico to 51% in India), far above clinician-diagnosed rates of about 0.5 to 6.5% that the authors cite.
Weak evidence: Opt-in online panel with 4 to 21% of records removed for quality; the questionnaire cutoff measures reported symptoms, not diagnosed illness. Do not treat as population prevalence.
Source: Palmer & Kattari 2026, J Xenobiotics, Journal of Xenobiotics Link to this fact
Health effects / Review of other studies
In six small case-control studies reviewed in 2026 (30 to 80 per group), children with ADHD had different gut bacteria on average (lower alpha diversity, fewer Lactobacillus and Bifidobacterium, lower fecal short-chain fatty acids), but no study measured chemical exposure, the microbiome and ADHD in the same children.
Weak evidence: Cross-sectional, heterogeneous methods; one tabulated study is itself a meta-analysis; effect sizes not reported.
Source: Wu 2026, Biological Psychiatry Global Open Science Link to this fact
Health effects / Review of other studies
The proposed route from chemical exposure through gut dysbiosis (barrier leak and inflammation, fewer short-chain fatty acids, stress-hormone dysregulation) to ADHD is a hypothesis: the supporting barrier, inflammation and HPA data are from rodents or from other conditions, and the review's only EED-linked human microbiome evidence is two cross-sectional urine studies.
Weak evidence: Animal doses described as often supraphysiological; mediation was never tested; the review's own text says direct evidence is lacking.
Source: Wu 2026, Biological Psychiatry Global Open Science Link to this fact
Hidden ingredients / Review of other studies
As early as 2004, a letter in Environmental Health Perspectives warned that fragrances can draw on thousands of chemicals and that most fragranced products had never been tested for human toxicity.
Weak evidence.
Caveats
The '4,000' figure comes from a 1991 book (Ashford & Miller) and describes untested products, not chemicals; later counts run ~3,000. Date 2020, now read as primary, corroborates 'thousands' as the right order of magnitude for the RIFM inventory (~2,600 active + ~3,500 discontinued) and separately states many individual fragrance materials lack toxicity data for standard endpoints — closer to Curtis's 'never tested' claim than any inventory count — but that is about individual chemicals with read-across-fillable data gaps, not about untested products, and does not confirm Curtis's specific '>4,000' figure.
Source: Curtis 2004, Environmental Health Perspectives Link to this fact
Hidden ingredients / Other evidence
A 2015 student lab analysis of 12 popular US perfumes and body sprays found 14-33 separate organic chemicals in each product (130 in all), while US law lets the label say just "fragrance".
Weak evidence: Identities are unconfirmed library matches and were never published; counts depend on the detection threshold. Pair with Steinemann 2011 rather than citing alone.
Source: Lee 2015, Young Scientist Journal (Vanderbilt University) Link to this fact
Hidden ingredients / Government agency
The industry safety panel's own risk calculation for PFOA (a persistent 'forever chemical' associated with PTFE manufacture) in lipstick relies on a single chemical supplier's claim of under 25 parts per billion in the raw material before it is formulated into a product — no actual PTFE-containing lipstick was tested for PFOA.
Weak evidence.
Caveats
The <25 ppb figure and the resulting '755-fold below EPA's advisory' conclusion are worst-case arithmetic on an unverified, pre-formulation raw-material claim, not a measurement of any real cosmetic product.
Source: CIR 2018 Industry-funded Link to this fact
Hidden ingredients / Other evidence
In a check by the review's authors, 11 of 22 randomly selected GRAS notices that FDA let pass with 'no questions' included no data on how the body absorbs, distributes, metabolizes, and excretes (ADME) the chemical.
Weak evidence: Very small sample (22), selection described in one sentence, notices up to about 2011; no statistical analysis. A signal of a gap, not a national rate.
Source: Maffini 2013, Comprehensive Reviews in Food Science and Food Safety Link to this fact
Hidden ingredients / Other evidence
GOTS 8.1's list of prohibited hazard statements for general chemical inputs covers carcinogens, mutagens, reproductive toxicants, organ toxicants, and endocrine disruptors but, as printed, not skin (H317) or respiratory (H334) sensitizers, so sensitizing chemicals are only banned by name for dyes.
Weak evidence: Reading of the printed list; other GOTS documents may add restrictions, and certification relies on approved inputs, not this list alone.
Source: GOTS 8.1 (2026) Link to this fact
Hidden ingredients / Measured in people or real products
In the same study, scented household cleaning products were not linked to higher levels of any measured chemical, and urine BPA was lower in children from homes that used them (ratio 0.69, 95% CI 0.49-0.98), so 'scented products' did not behave as one exposure.
Weak evidence: Likely chance or residual confounding on a wide multi-model estimate; shows heterogeneity of product categories rather than a protective effect.
Source: Fandiño-Del-Rio 2024, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Hidden ingredients / Other evidence
Few surveyed UAE women knew how fragrance is regulated: only 11.9% knew fragrance chemicals need not be fully disclosed on labels, 30.2% knew fragranced products emit hazardous air pollutants, and 82.2% believed natural ingredients are healthier.
Weak evidence.
Caveats
Open-link snowball sample of 461 women, mostly young and university-educated; self-report, no exposure measurement; not weighted, so not a UAE prevalence. Knowledge items copied from Klaschka/Steinemann; Germany 2019 gave 27.5% and 55.6% on the disclosure and natural items.
Source: AlBlooshi 2026, Frontiers in Toxicology Link to this fact
Indoor air / Measured in people or real products
In a week-long study of 7 working adults in Leipzig, the air at home made up 42-73% of the airborne chemicals they breathed, more than the outdoor air or their workplaces.
Weak evidence: N=7, one week, 25 VOCs; home share includes infiltrated outdoor air.
Source: Gokhale 2008, Science of the Total Environment Link to this fact
Indoor air / Other evidence
Baking soda raised the pH of the waste liquid from about 6 to 8.0-8.2 and lowered volatile acids by 17-23%, yet ammonia in the liquid rose (270 to up to 330 mg/L), so a deodorizer that cuts perceived odor can still shift which smelly chemicals are present.
Weak evidence: Ammonia was measured in the liquid, not the air, and the authors' argument that little of it evaporates at pH 8.2 is unmeasured reasoning.
Source: Qamaruz-Zaman 2015, Waste Management Link to this fact
Indoor air / Other evidence
CTV reported, from her letters, that indoor cigarette and cannabis smoke moved through her building's ventilation, that more chemical cleaners were used in hallways, and that she sealed her bedroom vents and lived mostly in that room.
Weak evidence.
Caveats
Her account via CTV; the Salvation Army, her landlord, replied only "we have nothing further to add" to her allegations. No air measurements. Death by MAiD is the subject; add 988 line in published use.
Source: CTV News, April 2022 (via Smoke-Free Housing BC; redacted copy), CTV News (news article) Link to this fact
Indoor air / Other evidence
The authors advised limiting ozone and reactive scent chemicals such as pine and citrus oils in cleaners, maintaining ozone-emitting copiers, and discouraging ozone 'air cleaners' for odor removal.
Weak evidence: Precautionary advice from the authors on mouse data and no human exposure test at the time; the paper says human studies are needed to set levels.
Source: Wolkoff 2000, Indoor Air Industry-funded Link to this fact
Indoor air / Other evidence
Personal-use scented products (perfumes, colognes, hair treatments) release their ozone-reactive chemicals close to the breathing zone, so inhaled doses of the reaction products can be larger than room-average models predict.
Weak evidence: A single supporting chamber citation, stated as a qualitative point; no dose given here.
Source: Weschler 2006, Environmental Health Perspectives Link to this fact
The industry / Journalism
The first press coverage of a 2011 study finding 133 undisclosed chemicals in 25 best-selling scented products, in the US government's environmental-health journal, quoted no manufacturer or industry group; the underlying numbers should be cited from the study itself (Steinemann 2011).
Weak evidence: Media-coverage note only; all product numbers belong to the primary src-2011-fragranced-consumer-products-chemicals-emitted-ingredients-unlisted.
Source: Potera 2011 (EHP news), Environmental Health Perspectives Link to this fact
The industry / Review of other studies
The author of a 2023 clinical review arguing that chemical sensitivity is primarily psychogenic (not caused by product chemistry) previously received partial, later-withdrawn funding for an uncompleted IEI genetics study via an unrestricted grant from the Research Institute for Fragrance Materials, the fragrance industry's own research and trade body.
Weak evidence.
Caveats
The funding is disclosed by the author, was withdrawn before the study was completed (due to poor enrollment, not a documented data or conclusions issue), and does not by itself invalidate the paper's clinical arguments; it is a conflict-of-interest fact worth weighing, not proof of bias in this specific manuscript.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
The industry / Measured in people or real products
A 2022 Korean study proposes prioritizing the specific hormone-disrupting chemical combinations that most often turn up together in household products, rather than testing chemicals one at a time, for future mixture-toxicity testing and regulatory management.
Weak evidence: This is a testing-prioritization proposal based on ingredient co-occurrence, not new toxicity data showing that any of the proposed mixtures cause harm.
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
The industry / Other evidence
An earlier FDA-lab study found that musk xylol, a synthetic musk fragrance ingredient, did move out of a 24-hour skin reservoir and into the bloodstream over time, unlike the self-tanner and hair-dye chemicals in the 2004 follow-up study.
Weak evidence: Cited secondhand from Yourick 2004's discussion; the Hood 1996 primary source has not been independently read and ingested into this evidence base.
Source: Hood 1996, cited in Yourick 2004, Toxicology and Applied Pharmacology Link to this fact
The industry / Other evidence
EWG's 2006 annual report listed its donors only in dollar bands (top band $250,000 or more: Hewlett, Joyce, Luce, and Park Foundations plus one anonymous donor), and no chemical, fragrance, or cosmetics company is evident in the list.
Weak evidence: Bands not amounts; anonymous donors are undisclosed; one year only; EWG is an advocacy group with its own agenda, so 'no industry money' is not the same as 'unbiased'.
Source: EWG 2006 Annual Report, EWG annual report (PDF) Link to this fact
The industry / Review of other studies
EWG counted 35 of the 91 ingredients in the tested fragrances as not assessed by the industry panels CIR, IFRA, or RIFM (66% of the secret chemicals versus 19% of those on labels).
Weak evidence.
Caveats
'Assessed' was judged from public sources only (RIFM's study list is not public); the report gives IFRA's count as 27 of 91 in one place and 22 of 91 in another, and 35 unassessed splits 11 plus 25 (=36).
Source: Sarantis et al. 2010 (Not So Sexy, Canadian edition) Link to this fact
The industry / Other evidence
In a 2006 reply, vom Saal and Hughes said 100% of animal studies showing low-dose BPA effects were government-funded and 100% of chemical-corporation-funded studies found none, and that the Harvard Center for Risk Analysis report disputing low-dose effects was funded by the American Plastics Council and reviewed only 19 studies.
Weak evidence.
Caveats
The authors' own tally, restated without new data; they say 'over 125 experiments' while the 2005 review counted 115; the authors are academic advocates for the low-dose view (declared no competing financial interests).
Source: EHP letters 2006, Environmental Health Perspectives Link to this fact
Laws and loopholes / Review of other studies
Fewer than 20% of the roughly 3,000 high-production-volume (HPV) chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Sealey 2016 relays this figure faithfully from Landrigan 2010, but Landrigan 2010's own citation to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks), is not supported: Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints.
Source: Sealey 2016 (citing Landrigan 2010), Environment International Link to this fact
Laws and loopholes / Measured in people or real products
Musk ambrette, banned in the EU for years, was still detected in the blood of 2 of 100 young Austrians tested, and testing the specific lotion and perfume one of them used did not find musk ambrette in the product itself, so the source of the banned chemical could not be pinned down.
Weak evidence.
Caveats
N=2; the tested products were negative for musk ambrette, so contamination, an unlisted supply-chain source, or a different untested product cannot be distinguished; no source identified.
Source: Hutter 2009, Science of the Total Environment Link to this fact
Laws and loopholes / Review of other studies
A leading pediatric environmental-health review states that fewer than 20% of the roughly 3,000 high-production-volume industrial chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Landrigan 2010 attributes this figure to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks): Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints. The citation does not support the specific number or endpoint claimed.
Source: Landrigan 2010, Current Opinion in Pediatrics Link to this fact
Laws and loopholes / Government agency
No US program requires VOC emission testing of cleaning products: EPA Safer Choice certifies fragrance-free products but, per the authors, does not require or disclose emission testing, and the chamber data show hundreds of emitted chemicals missing from labels and industry databases.
Weak evidence.
Caveats
EWG-authored (advocacy nonprofit that ranks cleaners and licenses EWG VERIFIED to cleaner makers); Skyline Foundation grant; unblinded; The authors' characterization of Safer Choice (2016 reference); not independently checked against current program rules.
Laws and loopholes / Other evidence
EWG calls the lack of public safety information on chemicals in everyday products 'a major failing of the nation's outdated chemical policy' and says manufacturers and government 'largely leave consumers in the dark' about cleaning-product contents.
Weak evidence: Advocacy-organization position in 2012, with no data or citation in this piece.
Source: Andrews, EWG, 2012 (web page) Link to this fact
Laws and loopholes / Government agency
The EPA work plan says ADBAC is subject to EPA's Endocrine Disruptor Screening Program but reports no endocrine screening results, and notes that being on a screening list does not mean a chemical is a known or likely endocrine disruptor.
Weak evidence: The document contains no endocrine data; absence of results here is not evidence either way.
Source: US EPA 2017 Link to this fact
Laws and loopholes / Other evidence
Inclusion Canada says a woman with multiple chemical sensitivities was forced to live in one room from October 7, 2019, after the Ontario Human Rights Tribunal did not provide safe air quality in her apartment.
Weak evidence.
Caveats
Advocacy post by an organization, written a year later; not independent reporting. Attribute to Inclusion Canada. The post gives no Tribunal file number, date or order; the Tribunal context rests on one sentence.
Source: Inclusion Canada: Remembering Sophia (advocacy post, Feb 22, 2023; redacted copy), Inclusion Canada blog post Link to this fact
Laws and loopholes / Other evidence
Disability ethicist Heidi Janz says that Sophia, a Toronto woman with MCS who died by MAiD in 2022, asked her to keep telling her story "in the hopes that other people wouldn't have to make the decision that she did."
Weak evidence: Single interview testimony relayed through a support person; the transcript is reconstructed from page HTML; no documents.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
A friend of Sophia says an attempt to seal Sophia's building made conditions worse because the person doing the work "really wasn't qualified to understand the way the air movement was working in the building," and that Sophia chose MAiD afterward.
Weak evidence.
Caveats
One friend's recollection; contractor, building and dates unidentified; not corroborated by any record on this page; speaker's account is not a finding about why Sophia sought MAiD.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
Janz says she believes Sophia had spent two years writing to local, provincial and federal officials about her housing situation, with doctors also advocating, without result.
Weak evidence: Testimony only; the same episode gives her age as 51 (host) and 53 (Janz), so details recalled by speakers are not independently confirmed.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
Janz argues that the choice of MAiD cannot be considered free for disabled people until they have free choice in where, with whom and how they live, and that without safe, affordable housing and supports MAiD "amounts to a eugenics program."
Weak evidence: Stated opinion of one disability-rights activist; she says it is strong language; this page records the position, it does not assess it.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
Janz says that under the UN Convention on the Rights of Persons with Disabilities governments must ensure access to safe housing and safe environments for people with MCS, and that Canada, though a signatory, tends to ignore those commitments.
Weak evidence: Opinion on treaty compliance; no legal analysis in the episode.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
Janz says clinicians who cannot or will not distinguish illness from chemical exposure in housing are being discriminatory and have an ethical duty to work harder to diagnose those factors.
Weak evidence: Ethicist's opinion; no clinical evidence presented.
Source: Chemical Sensitivity Podcast ep. 101, 2026 Link to this fact
Laws and loopholes / Other evidence
Station wastewater treatment in Antarctica (biological treatment with UV or chlorine) is judged by the authors to be ineffective for personal-care chemicals, and one-third of permanent and two-thirds of summer stations have no treatment.
Weak evidence: Efficacy is asserted, not quantified for these compounds; the authors admit plant conditions differ too much to compare treatments.
Source: Balakrishna 2023 (review), Environmental Research Link to this fact
Skin allergy / Measured in people or real products
Most patients who reacted to oxidized scent chemicals (58%) also had other fragrance allergies or a history of reacting to fragranced products.
Weak evidence: 31 positive patients.
Skin allergy / Other evidence
Across three chemical-intolerance case studies with symptom improvement tied to reduced VOC exposure, blood IgE allergy panels for 16 common indoor/outdoor/food antigens did not track or explain the symptom changes, and only 2 of the full 37-patient cohort (5.4%) had elevated antibodies to both dust mite and cockroach allergens.
Weak evidence.
Caveats
Uncontrolled case-series observation; absence of IgE elevation does not rule out other allergic or non-IgE immune mechanisms, and the paper does not test a specific non-allergic mechanism directly.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Skin allergy / Review of other studies
Fragrance causes both irritant and allergic contact dermatitis, among other adverse skin reactions, and fragrances are the most frequent chemicals causing contact dermatitis overall.
Weak evidence.
Caveats
Narrative review statement, not a ranked prevalence study; does not establish that contact dermatitis (from any cause) is the single most common adverse reaction to skincare products in general, only that fragrance is a leading cause of contact dermatitis specifically and that it can be either irritant or allergic.
Source: Pastor-Nieto 2021, Current Treatment Options in Allergy Link to this fact
Skin allergy / Review of other studies
Fragrance chemicals are also used as food flavorings, and dermatologists consider systemic contact dermatitis from fragrance-related food flavorings in fragrance-allergic patients whose eczema does not clear after 6 weeks of full topical fragrance avoidance.
Weak evidence: Clinical management guidance from a narrative review, not a measured ingestion-exposure or prevalence study; does not quantify how often food flavorings are the actual culprit.
Skin allergy / Other evidence
The National Eczema Association's Seal of Acceptance certification criteria exclude chemical UV-absorber sunscreens, accepting only physical (mineral) sunscreens containing titanium, zinc, or iron oxide.
Weak evidence.
Caveats
This reflects one certification body's precautionary ingredient-exclusion criteria for eczema-prone skin, not measured comparative allergic-contact-dermatitis incidence rates between mineral and chemical UV filters — no such comparative rate data were found in our evidence base or in this pass. Do not read this as evidence that mineral filters cause fewer ACD reactions in the general population, only that this eczema-focused body's rules treat them as the safer default.
Source: National Eczema Association 2026 Link to this fact
Skin allergy / Other evidence
Hairdressers who wore gloves during dye application did not have significantly lower hand loads of hair-dye chemicals than those who did not, but the gloves were often re-used for months, put on after mixing, or turned inside out, and glove users did the more hand-intensive whole-head jobs.
Weak evidence: Glove use was confounded with task and technique; 3 vs 1 hairdressers had PPD; not a test of properly used single-use gloves.
Source: Lind et al. 2005, The Annals of Occupational Hygiene Link to this fact
Skin allergy / Other evidence
Acetophenone azine, a chemical found in foam (EVA) shin guards, shoe insoles, and flip-flops, has caused allergic skin reactions in a small number of young athletes in Europe and Canada.
Weak evidence: Roughly a dozen documented patients, all from case literature; no prevalence data; the column is a society award announcement.
What you can do / Measured in people or real products
Childcare rooms with more fresh-air exchange had lower levels of several of the chemicals measured.
Weak evidence: Bivariate correlations, 34 rooms.
What you can do / Review of other studies
Old, long-opened scented products are more allergenic than fresh ones, because the scent chemicals oxidize on contact with air.
Weak evidence.
Caveats
Time course is primary for lavender oil (Hagvall 2008: LLNA EC3 36% fresh -> 23% at 10 weeks -> 4.4% at 45 weeks in the same batch), but in neat oil in open lab flasks, not formulated products as stored. Kern 2014 first closed part of this gap (39 fine fragrances + 29 antiperspirants, no accumulation over 9 months accelerated storage); Natsch 2019 extends this to 104 products across more categories (adding limonene, creams, lotions) and to multi-year real-time storage (two fine fragrances tracked 3-6 years at room temperature, no accumulation), plus tests products donated by allergic patients themselves (also negative for hydroperoxide). Downgraded to avoid because the specific claim — that aging/opening itself makes a product more allergenic via in-container oxidation — has now failed two independent, broader industry market surveys with no non-industry evidence on the other side; creams, lotions, and fine fragrances/antiperspirants are covered, though essential oils, raw materials, and other categories remain untested and are not covered by this downgrade. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
What you can do / Hypothesis
Air a room or clean it instead of scenting it: non-chemical alternatives such as opening windows and better hygiene are the first step in Klaschka's ten-step hierarchy for reducing fragrance exposure.
Weak evidence: Expert recommendation; not tested in the paper.
Source: Klaschka 2020, Environmental Sciences Europe Link to this fact
What you can do / Review of other studies
Wearable personal chemical-exposure monitors with audible threshold alarms ("eNose"-type devices) are proposed as a future tool to help people track real-time chemical exposure and correlate it with symptom onset, alongside biomarker testing (blood/urine for substances or metabolites) when intoxication is suspected.
Weak evidence.
Caveats
A forward-looking recommendation in the review's discussion/outlook section, not a validated or clinically deployed diagnostic tool; no accuracy, sensitivity, or outcome data for any such device is cited.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
What you can do / Review of other studies
For people whose fragrance/chemical reactions have a strong anxiety or panic component, mental-health referral, stress management, relaxation training, graded psychological desensitization to trigger odors, and (if needed) low-dose SSRIs are a recommended management approach, used alongside (not instead of) ruling out and treating any real underlying allergic or respiratory disease.
Weak evidence.
Caveats
The author states outright that research on mental-health treatment efficacy specifically in IEI is limited, because many affected patients decline psychiatric referral; the recommendation rests on case reports and phobia-treatment analogy, not controlled trials in this population.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.