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 / Review of other studies
Across 13 independent qualitative studies from four countries, people with multiple chemical sensitivity consistently describe being kept out of everyday places by scented/chemical products, and losing jobs, income, or social relationships because of it.
Moderate evidence.
Caveats
Systematic review of qualitative (not survey) evidence; meta-aggregation of 53 findings from 13 small, mostly clinic/support-group/self-selected-website-recruited studies (sample sizes 4-203), none rated top quality by the review's own NICE checklist. Converges in direction with, but does not quantitatively confirm, Steinemann's self-report survey percentages already in our evidence base.
Source: Driesen 2020, Journal of Psychosomatic Research Link to this fact
Health effects / Test-chamber measurement
Telling people a real chemical exposure is a harmful industrial solvent versus a beneficial natural extract changed how irritating they rated identical 800 ppm acetone air and how many health symptoms (throat/nasal irritation, lightheadedness, nausea, drowsiness) they reported afterward, even though every group breathed the same concentration.
Moderate evidence: Single lab, single cohort, not independently replicated; co-funded by the Chemical Manufacturers' Association alongside NIH grants (coi/industry-funded).
Source: Dalton et al. 1997, Int Arch Occup Environ Health 69:407-417 Industry-funded Link to this fact
Health effects / Measured in people or real products
In a small Swedish clinic study, people whose breathing symptoms were triggered by scents and chemical irritants — but who had normal lung function and negative allergy and asthma tests — coughed much more after inhaling capsaicin (the hot-pepper compound) than either people with verified asthma or healthy volunteers (93 vs 23 average coughs at the highest dose, P<0.001).
Moderate evidence.
Caveats
Small (n=10 per patient group, n=28 healthy controls), single-clinic study; capsaicin dosing was open-label (patients not told doses would increase) rather than placebo-blinded, so it is a correlational patient-vs-comparator design, not an intervention.
Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact
Health effects / Measured in people or real products
The extra coughing in these chemically sensitive patients could not be explained by asthma: their lung function, methacholine reactivity, and skin-prick allergy testing were all normal, yet they still coughed dose-dependently to inhaled capsaicin, and even to a plain saline control, while a separate group of people with verified asthma did not cough more than healthy volunteers.
Moderate evidence.
Caveats
Single small clinic sample (n=10 per patient group); normal methacholine and skin-prick tests were inclusion criteria for the chemically sensitive group, not an independent finding in an unselected population.
Source: Millqvist, Bende & Löwhagen 1998, Allergy Link to this fact
Health effects / Government agency
As of 1998, EPA's own environmental-health office stated that certain types of childhood cancer were increasing but the causes were largely unknown, and that the agency lacked a reliable basis to determine whether most untested high-production-volume industrial chemicals were safe or unsafe for children.
Moderate evidence.
Caveats
A general statement about data gaps as of 1998, not a study establishing or ruling out any specific chemical-childhood-cancer link; the paper explicitly states EPA does not know how many, if any, childhood cancers are caused by these exposures.
Source: Goldman 1998, Environmental Health Perspectives Link to this fact
Health effects / Self-reported survey
People with asthma were about 4 times more likely to report a doctor's diagnosis of environmental illness/multiple chemical sensitivity than people without asthma (19.0% vs. 4.6%), and over twice as likely to self-report unusual sensitivity to everyday chemicals (31.5% vs. 13.9%).
Moderate evidence.
Caveats
Cross-sectional association from a single population survey with no independent replication cited here; does not establish that asthma causes or is caused by chemical sensitivity, only that they co-occur more than chance in self-report.
Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact
Health effects / Self-reported survey
Women were about 1.6 times more likely than men to self-report sensitivity to more than one everyday chemical, after adjusting for other factors, though doctor-diagnosed MCS itself was not significantly associated with sex.
Moderate evidence.
Caveats
Single population survey; unadjusted sex ratios for this item (F:M ~2.3) sit well below the ~4:1 ratio later found in a national survey using the same question wording, so the sex effect size varies by sample.
Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact
Health effects / Self-reported survey
Reports of doctor-diagnosed multiple chemical sensitivity and self-reported chemical sensitivity were spread fairly evenly across race/ethnicity, income, education, marital status, and geography in a representative California sample, unlike clinic-based case series which have reported a predominance of middle- to upper-class white women.
Moderate evidence.
Caveats
Homogeneous distribution is consistent with either a real physiologic mechanism or widespread cultural apprehension about chemicals; the study explicitly does not distinguish between these explanations.
Source: Kreutzer, Neutra & Lashuay 1999, American Journal of Epidemiology Link to this fact
Health effects / Other evidence
Methacrolein activates the sensory-irritant receptor by chemically reacting with it (like acrolein), not by simple physical adsorption, and its carbon-carbon double bond — not its aldehyde group — is the key reactive feature; it is roughly six times less potent than acrolein itself.
Moderate evidence: Mechanistic inference from a potency-ratio comparison across compounds tested in different (cited) studies, not a direct receptor-binding assay.
Source: Larsen & Nielsen 2000, Toxicology Letters Industry-funded Link to this fact
Health effects / Animal study
In the same study, a cotton tee-shirt that had already been dried with a fabric-softener pad — not the pad itself — still emitted enough residual chemical to cause significant sensory irritation in mice (49% of breaths, versus 6% for an unwashed new shirt), at a much lower bulk air concentration (86 ppm) than the raw pad's headspace.
Moderate evidence.
Caveats
Single lab, one brand tested, n=8 exposed mice; airflow limitation (7%, not significant except in 1 of 8 mice) and pulmonary irritation were not significantly changed from the new-shirt control.
Source: Anderson & Anderson 2000, Journal of Toxicology and Environmental Health, Part A Link to this fact
Health effects / Lab study (cells or chemistry)
In a lab test, four common fragrance/flavor chemicals found in essential oils – citral, geraniol, nerol, and trans-anethole – weakly activated the human estrogen receptor, and eugenol weakly blocked it, but all needed concentrations 100,000 to 1,000,000 times higher than the body's own estrogen to show any effect.
Moderate evidence: Single-lab yeast reporter assay, confirmed by direct receptor-binding but not by a second cell-based assay (Ishikawa cells, negative for all compounds).
Source: Howes et al. 2002, Journal of Pharmacy and Pharmacology Link to this fact
Health effects / Lab study (cells or chemistry)
Linalool and eucalyptol (1,8-cineole) – two of the main scent chemicals in lavender and tea tree oil – showed no estrogen-receptor activity at all in this yeast test, alongside 14 other common essential-oil constituents that were tested and found inactive.
Moderate evidence.
Caveats
Single assay type (yeast ERE reporter); does not test androgen-receptor activity or steroid-synthesis enzymes, which other studies show linalool and eucalyptol can affect differently.
Source: Howes et al. 2002, Journal of Pharmacy and Pharmacology Link to this fact
Health effects / Self-reported survey
In a 2002-03 US national telephone survey of 1,054 randomly selected adults, 11.2% self-identified as unusually sensitive to everyday chemicals such as cleaning products, perfume, and detergents, and 2.5% said they had been medically diagnosed with multiple chemical sensitivity (MCS).
Moderate evidence.
Caveats
Single national random-digit-dial telephone survey; self-report with no clinical verification of hypersensitivity or diagnosis; the earliest in a cross-country series of self-report chemical-sensitivity prevalence figures.
Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Self-reported survey
Among the 11.2% of US adults who self-identified as chemically hypersensitive, about 2 in 3 (66.7%) described their symptoms as severe or moderately severe, and about 1 in 7 (13.2%) said they had lost a job because of it; 72.7% had changed their household or personal-care products.
Moderate evidence: Self-report severity and lifestyle-effect items in a subgroup of n=117-122; no clinical verification.
Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Self-reported survey
In this national survey, women were reported as chemically hypersensitive at roughly 4 times the rate of men (about 15.9% of women vs 4.0% of men, wiki arithmetic from the paper's cross-tabulation), and prevalence rose steadily with age from about 7% under age 36 to about 15% over age 50.
Moderate evidence.
Caveats
Sex- and age-specific prevalence rates are evidence base arithmetic from the paper's Table 4 cross-tabulation, not stated directly by the authors; single national self-report survey.
Source: Caress & Steinemann 2003, Archives of Environmental Health: An International Journal Link to this fact
Health effects / Self-reported survey
In a 1999-2000 telephone survey of 1,582 randomly selected adults in the Atlanta, Georgia metro area, 12.6% self-identified as unusually sensitive to everyday chemicals, and 3.1% reported a medical diagnosis of environmental illness or multiple chemical sensitivity (MCS).
Moderate evidence: Single regional random-digit-dial telephone survey; self-report with no clinical verification of hypersensitivity or diagnosis.
Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact
Health effects / Self-reported survey
Among Atlanta-area adults who reported chemical hypersensitivity, about 1 in 7 (13.5%) said they had lost a job because of it (1.8% of the entire sample), and about 3 in 10 (29.9%) said it made shopping in stores difficult.
Moderate evidence.
Caveats
Self-report, single regional survey; per the primary brief (Caress & Steinemann 2004, Table 1) these items were asked of 'yes' plus 'not sure' respondents (denominators 214-215), not only the 199 'yes'.
Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact
Health effects / Self-reported survey
In the same follow-up, the most common symptoms reported after a chemical exposure were headache (88.4%) and burning eyes (76.8%), followed by asthma-like breathing difficulty (59.4%) and nausea or stomach distress (55.1%).
Moderate evidence.
Caveats
Small, non-random follow-up sample (n=69); self-reported symptoms with no clinical verification; the symptom-question cluster had the lowest internal-consistency score (Cronbach's alpha 0.5054) of the three question clusters tested.
Source: Caress & Steinemann 2003 (EHP), Environmental Health Perspectives Link to this fact
Health effects / Measured in people or real products
In a PET brain-imaging study of 12 women with multiple chemical sensitivity (MCS) and 12 matched controls, MCS subjects activated the brain's core odor-processing regions (amygdala, piriform, and insular cortex) LESS than controls when smelling most odorants, not more, despite resting brain activity being normal in both groups.
Moderate evidence: N=12/group, women only, single center (Karolinska), no independent replication of this exact PET paradigm in our evidence base yet.
Source: Hillert et al. 2007, Human Brain Mapping Link to this fact
Health effects / Measured in people or real products
In a double-blind chamber study of 130 healthy women, those who scored high on a validated chemical-odor-intolerance questionnaire did not have worse symptoms, stress-hormone (cortisol) levels, or cognitive/driving-simulation performance when exposed to an indoor VOC or VOC-plus-ozone mixture, compared to women who scored low on the same questionnaire.
Moderate evidence.
Caveats
Single lab, subsample of 130 (40 high-CI, 46 low-CI, tertile split); healthy, non-smoking women only; people with clinically significant MCS/illness behavior were excluded, and the authors could not recruit volunteers at the extremes of chemical intolerance; one 140-minute exposure, not repeated or chronic exposure.
Source: Fiedler 2008, Psychosomatic Medicine Link to this fact
Health effects / Measured in people or real products
Women prone to negative affect (anxiety, worry, distress) became more anxious after a public-speaking stressor during an indoor-chemical exposure session, regardless of what was in the air (clean air, VOCs, or VOCs plus ozone) – but they did not show higher cortisol or more physical (non-anxiety) symptoms than women low in negative affect.
Moderate evidence.
Caveats
Tertile-split subsample (45 high-NA, 48 low-NA) of 130 healthy women; excludes people with diagnosed psychiatric conditions; a public-speaking task is a milder stressor than daily-life stress.
Source: Fiedler 2008, Psychosomatic Medicine Link to this fact
Health effects / Measured in people or real products
People who scored high in chemical intolerance or negative affect rated the same chemical exposure and their own symptoms as more annoying and more distressing than other participants did, even though their measured symptom counts, cortisol, and driving/attention performance were no different.
Moderate evidence: Annoyance/distress were retrospective, subjective 5-point ratings, not the same structured symptom-severity measure used for the main null; single study, healthy women only.
Source: Fiedler 2008, Psychosomatic Medicine Link to this fact
Health effects / Self-reported survey
In the same study, chlorine/bleach exposure (adjusted OR 1.01, 95% CI 0.47-2.18), latex glove use (adjusted OR 0.69, 95% CI 0.32-1.51), and glutaraldehyde exposure (crude OR 1.31, 95% CI 0.53-3.23) showed no significant association with reported asthma; QAC exposure was the only occupational chemical exposure that remained statistically significant after adjustment.
Moderate evidence.
Caveats
A null result in one cross-sectional study does not prove these exposures are safe; some comparisons (e.g. glutaraldehyde, chlorine/bleach) had small exposed groups and wide confidence intervals, so a true effect could have been missed for lack of statistical power.
Source: Gonzalez 2014, Clinical & Experimental Allergy Link to this fact
Health effects / Self-reported survey
Using an expert job-task-exposure matrix, high occupational exposure to formaldehyde (OR 1.33), glutaraldehyde (OR 1.18), hypochlorite bleach (OR 1.18), hydrogen peroxide (OR 1.19) and enzymatic cleaners (OR 1.33, the only one significant at P<0.001) was each associated with poorer asthma control in US nurses, versus low exposure to the same chemical.
Moderate evidence.
Caveats
Exposure levels come from a job-task-exposure matrix built from a separate reference sample's questionnaire responses, not direct measurement; 95% confidence intervals for these specific odds ratios were shown only as graphical whiskers in the source figure, not printed, so are not reported as exact numbers here.
Source: Dumas 2017, European Respiratory Journal Link to this fact
Health effects / Review of other studies
A review of controlled chamber studies (carbon dioxide, ammonia, formaldehyde, sulfur dioxide, glycol/glycol-ether mixtures) found no consistent evidence that people with allergic rhinitis or mild asthma are more sensitive to sensory-irritant chemicals than non-allergic people.
Moderate evidence.
Caveats
The underlying chamber studies excluded moderate and severe asthma/allergy by design and tested mostly non-fragrance irritants; one exception was found (allergic subjects more sensitive to n-propanol specifically), and the review is narrative, not a systematic review with a defined search protocol.
Source: Nielsen & Wolkoff 2017, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Health effects / Self-reported survey
The study found no association between childhood or adult hair product or hair oil use and mammographic breast density, a separate, strong breast-cancer risk factor, suggesting that if hair-product chemicals affect breast cancer risk, it may be through pubertal timing rather than breast density.
Moderate evidence: Small sample (N=248) limits power to detect a true but modest effect on breast density; one adult product subgroup (hair dye) did show a small positive association with density.
Source: McDonald 2018, Environmental Health Link to this fact
Health effects / Review of other studies
People with chemical intolerance or multiple chemical sensitivity react more strongly than healthy controls in controlled chamber exposures to irritant chemicals, with derived sensitivity factors typically 1 to 3 times higher and, in some studies, up to about 20 times higher.
Moderate evidence.
Caveats
Objective physiological confirmation was rare across the underlying studies; most of the signal is in subjective symptom ratings, which can be influenced by odor perception and expectation.
Source: Mangelsdorf et al. 2021, Int J Hyg Environ Health, International Journal of Hygiene and Environmental Health Link to this fact
Health effects / Lab study (cells or chemistry)
Among 62 individually tested deodorant ingredients, only fragrance chemicals (plus one insect-pheromone contaminant) showed any estrogenic activity; no carrier, stabilizer, emulsifier, plasticizer, antitranspirant, or other active ingredient (including triclosan and BHT) tested positive.
Moderate evidence: Only 62 of the many ingredients found by GC/MS screening were selected for individual testing, based on frequency of occurrence; ingredients not selected were not tested at all.
Health effects / Review of other studies
Fragrance chemicals have been reported to cause immediate-type contact urticaria, photosensitivity reactions, and rarer miscellaneous effects such as depigmentation and orofacial granulomatosis, but the review characterizes all of these as currently rare and not causing significant clinical problems.
Moderate evidence: Causal relationship for the miscellaneous effects in Table 13 is explicitly stated by the review as "not always established beyond doubt" (mostly case reports).
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
Health effects / Lab study (cells or chemistry)
An academic in vitro toxicology screen of Lilial (butylphenyl methylpropional, the fragrance chemical banned from EU cosmetics in 2022) found no cytotoxicity, no mutagenicity in a mammalian gene mutation assay, no nephrotoxicity, and no NF-κB or NRF2 stress-pathway activation, in either Lilial itself or its major liver-generated (S9) metabolites, up to 100 µM.
Moderate evidence.
Caveats
Single academic lab, one round of testing, not yet independently replicated; a genotoxicity endpoint (γH2AX) in the same paper was inconclusive, not clean negative, so 'no adverse effect' does not extend to every endpoint tested.
Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact
Health effects / Lab study (cells or chemistry)
Using OECD/EPA guideline-validated receptor-transactivation assays (HeLa9903 for estrogen receptor, MDA-kb2 for androgen receptor), Lilial and its major liver metabolites showed no estrogen- or androgen-receptor agonist activity from 1 nM to 100 µM; the study's authors said they were unable to confirm the European Chemicals Agency's earlier suspicion that Lilial is an endocrine disruptor.
Moderate evidence: Single academic lab; this directly conflicts with a weaker, non-guideline finding from a different assay type (MCF7 proliferation) for the same compound — see contradiction.
Source: Jablonská 2023, Sci Rep 13:18536, Scientific Reports Link to this fact
Health effects / 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
Animal studies show that mixtures of endocrine-disrupting chemicals can produce additive effects even when every chemical in the mixture is present at a level too low, on its own, to cause any observable effect, meaning many 'individually safe' exposures could add up to a harmful one.
Moderate evidence.
Caveats
Based on animal mixture studies cited in the report; the report itself states there are no data showing how real-world mixtures of hundreds of EDCs at low concentrations actually affect human or wildlife health.
Source: WHO/UNEP 2012 Link to this fact
Health effects / Government agency
Hormone-disrupting chemicals often do not follow a simple 'more dose equals more effect' pattern; some show non-monotonic dose-response curves, so standard toxicology testing at high doses, divided by a safety factor to estimate a low 'safe' dose, may miss real effects that occur only at low doses.
Moderate evidence: This is the report's own methodological critique of standard regulatory toxicology testing, not a finding about any specific chemical.
Source: WHO/UNEP 2012 Link to this fact
Health effects / Other evidence
A widely cited 2012 review (Vandenberg et al.) cataloged many examples of endocrine-disrupting chemicals producing non-monotonic (U-shaped) dose-response curves; an independent 2013 Danish government reanalysis of that same catalog found that 45% of its cited in vitro examples were artifacts of general cell toxicity rather than true hormone-mediated effects, and only 5 of 34 cited in vivo (whole-animal) examples showed clear evidence of a genuine non-monotonic response.
Moderate evidence.
Caveats
Known only secondhand through an industry-funded critique paper with a direct interest in this conclusion; the original Vandenberg et al. 2012 review and the DTU Food 2013 reanalysis should be read as primaries before this is treated as settled.
Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Health effects / Other evidence
The WHO-UNEP 2012 report changed its conclusion on PCBs and DDT causing adrenocortical hyperplasia (Cushing-like adrenal gland disease) in Baltic seals from 'uncertain association' in the WHO's 2002 report to 'sufficient evidence' of a causal link in 2012, without citing any new supporting data, while not addressing contrary findings that tie similar adrenal changes in other marine mammals to chronic stress rather than chemical exposure, and rat studies finding the opposite direction of adrenal effect (atrophy, not hyperplasia) from the same chemicals.
Moderate evidence: From an industry-funded critique paper; the underlying wildlife and rat studies have not yet been read as primaries by this evidence base.
Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Health effects / Other evidence
The WHO-UNEP 2012 report's claim that the rise in autism spectrum disorder (ASD) prevalence is at least partly caused by environmental factors, including endocrine-disrupting chemicals, rests on only two citations (from 1976 and 2007); separate, non-industry-affiliated research attributes much of the reported increase in ASD prevalence to changes in diagnostic criteria, broader case ascertainment, and diagnostic substitution (children previously diagnosed with intellectual disability now diagnosed with ASD) rather than to any confirmed environmental cause.
Moderate evidence.
Caveats
This does not establish that endocrine-disrupting chemicals play no role in ASD, only that the WHO-UNEP report's specific citations for an environmental/EDC contribution are thin; no causal chemical-to-autism claim is made or implied here.
Source: Lamb et al. 2014, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Health effects / Animal study
Repeated animal studies attribute transgenerational reproductive effects of endocrine-disrupting chemicals to epigenetic changes (DNA methylation, histone modification, noncoding RNA) transmitted through the germline to descendants who were never themselves exposed to the chemical, rather than to a new genetic mutation.
Moderate evidence.
Caveats
This is the accepted mechanistic framework across many of the cited rodent studies, but no human transgenerational endocrine-disruptor reproduction study exists to confirm the mechanism operates the same way in people.
Health effects / Review of other studies
Across multiple large studies and meta-analyses, people with higher levels of the plastic chemical bisphenol A (BPA) in their urine or blood have consistently higher rates of obesity and abdominal obesity; one meta-analysis found an 11% increase in obesity risk for every 1 ng/mL rise in blood BPA.
Moderate evidence.
Caveats
Nearly all human evidence is cross-sectional or short-follow-up observational; BPA exposure correlates with eating packaged and ultra-processed food, which is itself linked to obesity, so diet and lifestyle confounding cannot be excluded.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
Health effects / Review of other studies
In mouse, rat, and zebrafish studies, bisphenol A and phthalates such as DEHP promote weight gain by switching on the master fat-cell gene PPAR-gamma, boosting appetite-driving brain chemicals (neuropeptide Y and AgRP), and triggering low-grade inflammation in fat tissue, often at doses meant to mimic real-world human exposure.
Moderate evidence.
Caveats
These are animal and cell-culture mechanisms; extrapolation to human obesity risk is not established, and effects vary by species, sex, dose, and life stage in ways not yet mapped for humans.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
Health effects / Other evidence
In a 2004 FDA laboratory study, two of three chemicals that penetrated into skin and stayed there after 24 hours (a self-tanning ingredient and a hair-dye ingredient) were shown, using an extended 72-hour test, not to actually enter the bloodstream in any meaningful additional amount.
Moderate evidence: Single FDA lab, in vitro diffusion-cell system (not in vivo humans); findings are chemical-specific, not a general rule about skin-retained chemicals.
Source: Yourick 2004, Toxicology and Applied Pharmacology Link to this fact
Health effects / Government agency
Air fresheners accounted for only 0.58% of all 2.4 million chemical exposures reported to US poison control centers in 2005, and 95% of the resulting injuries were minor; deodorizers (the category containing air fresheners) ranked 20th of 23 product categories for pediatric poison-control exposures.
Moderate evidence.
Caveats
Poison-control call data undercounts chronic, low-dose, or misattributed exposures and cannot establish long-term health risk; EPA itself notes it has no way to verify whether asthma or other symptoms are correctly attributed to air fresheners by callers.
Source: EPA 2007, citing AAPCC 2005 Link to this fact
Health effects / Review of other studies
A 1950s-70s antiseptic called hexachlorophene showed how a chemical that binds tightly to the skin's outer dead layer can be both protective and dangerous: routine hexachlorophene baths cut newborn staph-infection admissions from about 6.5% to 0.6%, but when 18 French children were accidentally exposed to 6% hexachlorophene talc in 1972, four died and others developed permanent neurological damage from the same skin-binding property letting the chemical build up to toxic levels.
Moderate evidence.
Caveats
Historical case-series data as reported in a 2018 review citing 1950s-70s primary sources; the review does not re-verify the original studies' methods, and the toxic exposure was accidental overapplication (6% in talc powder to skin, some broken), not typical consumer use.
Source: Li, Cary & Maibach 2018, Archives of Dermatological Research Industry-funded Link to this fact
Health effects / Review of other studies
How long a chemical lingers in the outer layer of skin after being applied depends mainly on three things: its chemical structure (ionic/charged chemicals bind skin proteins more strongly), how hydrated the skin is, and how well the chemical dissolves in the product's carrier liquid — and, in one specific dataset (a set of six chemical warfare agent simulants), skin binding rose in step with how fat-soluble (lipophilic) the chemical was.
Moderate evidence.
Caveats
General mechanism synthesized from mixed antimicrobial, sunscreen, and warfare-agent-simulant studies (not fragrance ingredients); the lipophilicity relationship comes from a single dataset of six chemicals with no fragrance or cosmetic ingredients among them.
Source: Li, Cary & Maibach 2018, Archives of Dermatological Research Industry-funded Link to this fact
Health effects / Review of other studies
The Endocrine Society's April 2025 Position Statement defines an endocrine-disrupting chemical as "an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action," and states that because non-monotonic dose responses are common, it cannot be assumed there are non-zero thresholds below which EDC exposure is safe.
Moderate evidence.
Caveats
A professional society position, not a government/regulatory finding; the Society's own definition omits the WHO/IPCS requirement that the interference actually cause adverse health effects.
Source: Endocrine Society 2025 Link to this fact
Health effects / Other evidence
The Endocrine Society's definition of an endocrine-disrupting chemical covers interference with any aspect of hormone action, including hormone synthesis, not only interference at hormone receptors.
Moderate evidence.
Caveats
This is the definition as characterized in Sharma 2024's discussion of its own steroidogenesis-enzyme findings, not a direct quote from the Endocrine Society's own primary scientific statement (e.g., the 2009 or 2015 Endocrine Society Scientific Statements on EDCs, which are not themselves in our evidence base). It matches the widely used consensus phrasing but should ideally be corroborated against the primary statement if a stronger source is later ingested.
Health effects / Government agency
The WHO/UNEP 'State of the Science of Endocrine Disrupting Chemicals, 2012' report's Concluding Remarks state verbatim that endocrine disruptors are 'a global threat that needs to be resolved.'
Moderate evidence.
Caveats
IMPORTANT PROVENANCE NOTE: this exact sentence ('This is a global threat that needs to be resolved,' p.26, Section 14 'Concluding remarks') was verified directly against the primary report PDF already held in the vault (raw/papers/processed/2013-who-unep-state-science-endocrine-disrupting-chemicals.pdf, via pdftotext), NOT against the curated evidence base/sources markdown summary page, which paraphrases this report extensively but does not itself quote this specific sentence. A curator should add it to the source page's Key Findings before treating this as fully 'in our evidence base.' It is an expert-consensus statement of concern, not a new empirical finding.
Source: WHO/UNEP 2012 Link to this fact
Health effects / Measured in people or real products
People with multiple chemical sensitivity do not appear to have a more sensitive sense of smell at baseline; the evidence instead points to their brains habituating less than other people's brains do to a constant low-level chemical exposure.
Moderate evidence.
Caveats
Rests on one small ERP study (Andersson 2009, 21 vs 17 participants) that this review cites accurately for this specific finding; does not show whether reduced habituation makes exposure more hazardous, only that perception differs.
Source: Pellegrino 2017, Physiology & Behavior Industry-funded Link to this fact
Health effects / Other evidence
For the synthetic musk fragrance ingredient musk xylol, chemical still sitting in human skin 24 hours after a single application did not stay put: when an FDA lab extended testing to a full week, about three-quarters of the 24-hour skin reservoir had disappeared, while roughly 14-16% of the original applied dose had moved into the fluid representing the bloodstream side of the skin barrier.
Moderate evidence: Single FDA lab, in vitro excised human-skin model with only two human subjects in the extended-study cohort; not a living-human in vivo measurement.
Source: Hood 1996, Food and Chemical Toxicology Link to this fact
Health effects / Other evidence
About 16% of adult onset asthma in this British cohort (95% CI 3.8-27.1%) was estimated to be attributable to occupational chemical exposure of any kind, a population-attributable-fraction estimate comparable in size to the fraction attributable to ever having smoked (11.2%, 95% CI 2.6-19.1%).
Moderate evidence.
Caveats
This is the PAF for all occupational exposure combined (farming, printing, metalworking, textiles, cleaning, etc.), not a cleaning-specific or fragrance-specific estimate; the outcome is self-reported 'ever had asthma,' not spirometry-confirmed.
Health effects / Measured in people or real products
Among hotel workers directly handling cleaning products, bleach, and laundry chemicals, the average estimated excess lifetime cancer risk from inhaled VOCs (4.1 in 100,000) was about 40 times the EPA's 1-in-a-million screening threshold, driven more than two-thirds by formaldehyde (then chloroform and benzene), even though measured VOC concentrations were at the low end of those reported in US buildings generally.
Moderate evidence: Preliminary/screening-level risk estimate extrapolated from short-term (6-9h) measurements to a 40-hr workweek; small sample (2 hotels); not a measured cancer incidence.
Health effects / Self-reported survey
Migraine patients with interictal olfactory hypersensitivity scored far higher on a validated 5-item chemical odor intolerance index (pesticide, paint, perfume, new carpet, car exhaust) — 18.7 +/- 3.2 — than migraineurs without it (11.7 +/- 3.6) or headache-free controls (9.9 +/- 3.5), a clear dose-like gradient (all pairwise P <= 0.02).
Moderate evidence: Single-center, cross-sectional; the index is validated but coarse (5 items) and self-report.
Health effects / Measured in people or real products
Brominated flame-retardant chemicals (PBDEs) in Korean mothers' breast milk were among the highest levels measured anywhere in the world, comparable to or higher than North America, though the study's own calculated hazard quotients for infant intake of the three most abundant PBDEs were all below 1 (0.62, 0.42, and 0.19).
Moderate evidence.
Caveats
N=20 Korean mothers, 2007 samples; a hazard quotient below 1 reflects the study's own non-cancer reference-dose comparison for three congeners only (BDE-47, -99, -153), not a finding of safety for synthetic musks or for PBDE mixtures generally; the authors call for larger, longer-term studies.
Health effects / Measured in people or real products
Women whose menstrual products contained more n-nonane, benzene, or toluene (based on the group's prior product-testing data) had correspondingly higher urinary levels of those same chemicals: n-nonane β=6.60 log ng/g (95% CI 1.63-11.57, p=0.009), benzene β=0.85 (95% CI 0.13-1.58, p=0.02), toluene β=0.13 (95% CI 0.03-0.22, p=0.009).
Moderate evidence: First direct product-content-to-urinary-biomarker linkage in this research line; small pilot cohort (n=25); observational.
Source: Ding 2022, Journal of Women's Health Link to this fact
Health effects / Other evidence
A toxicokinetic model estimates that fat-soluble fragrance/solvent chemicals from feminine hygiene products (p-cymene, hexane, n-nonane) can build up in body fat to levels 1 to 4 orders of magnitude higher than in blood or urine, even though skin levels stay low.
Moderate evidence: Modeled, not directly measured in body fat; single research group's model not yet independently replicated.
Source: Lin 2025, Environmental Health Perspectives Link to this fact
Health effects / Other evidence
The flavor panel judges methyl salicylate (wintergreen oil) safe as a flavoring from a 50 mg/kg/day no-effect level in dogs; intake as an added flavoring is about 1,190 micrograms a person a day (0.02 mg/kg), giving a margin of about 2,500; the same chemical also appears in cosmetics and rubs where this food-only assessment does not count it.
Moderate evidence.
Caveats
Industry panel's calculation; the margin is a ratio of two industry-chosen figures; combined food plus cosmetic exposure is not assessed in either the flavor or the fragrance industry's review.
Source: Guengerich 2026 (FEMA Expert Panel), Food and Chemical Toxicology Industry-funded Link to this fact
Health effects / Self-reported survey
People with asthma or chemical sensitivity reported fragrance reactions far more often than the general public: air-freshener problems in 33.5% of asthmatics and 57.9% of the chemically sensitive vs 19.0% of all adults, and laundry-vent irritation in 21.2% and 39.8% vs 10.9% (2005-06).
Moderate evidence.
Caveats
Self-report; the chemically sensitive subgroup is small (about 11% of about 1,057, roughly 120 people per survey) and its second-survey value of 60.2% is printed identically in two different tables, so subgroup numbers may contain a copy error.
Source: Caress & Steinemann 2009, Journal of Environmental Health Link to this fact
Health effects / Self-reported survey
Among US adults with diagnosed asthma, 29.2% also described themselves as chemically sensitive and 9.6% had diagnosed multiple chemical sensitivity (two-survey average), against 11.4% and 3.2% in the whole sample.
Moderate evidence: Self-reported diagnoses without medical confirmation; simple averages of two surveys; association only, no direction of effect.
Source: Caress & Steinemann 2009, Journal of Environmental Health Link to this fact
Health effects / Measured in people or real products
The 17 fragrances together contained 24 chemicals EWG classed as skin sensitizers, about 10 per product (19 in Armani Acqua Di Gio); limonene was in 16 products, linalool in 14, and geraniol in 12.
Moderate evidence: Presence is lab- or label-based; sensitizer status is EWG's literature classification, not a potency or dose assessment; the sensitizer table omits one of the 17 products.
Source: Sarantis et al. 2010 (Not So Sexy, Canadian edition) Link to this fact
Health effects / Other evidence
In the same review, about 40% of migraine patients (40.1%, 95% CI 32.7-47.8) said an odor can trigger their attacks; among those naming odor triggers, perfume was the most common (65.0%), then smoke (36.3%) and household cleaners, bleach, or chemicals (29.0%).
Moderate evidence: Retrospective self-report; trigger vs premonitory aversion not separated; the same 40.1% figure also appears for in-attack hypersensitivity with a different CI.
Source: Briggs et al. 2025, World J Otorhinolaryngol Head Neck Surg, World Journal of Otorhinolaryngology – Head and Neck Surgery Link to this fact
Information, not medical advice. See also: myths we won’t tell you.