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.
Green, natural and unscented / Government agency
A product carrying the EPA Safer Choice 'fragrance-free' label can still have a smell, because ordinary functional ingredients such as surfactants and solvents can carry an odor without being classified as a fragrance material.
Moderate evidence: EPA states this directly; it is a definitional carve-out, not a measurement of any certified product's actual odor.
Source: US EPA Safer Choice Link to this fact
Green, natural and unscented / Other evidence
GOTS 8.1 contains no rule on perfume, scent, or aroma finishes in ordinary clothing; its only fragrance clause (COSMOS criteria) covers Group II personal-care textiles such as tampons and cotton buds, so a GOTS label does not mean fragrance-free clothing.
Moderate evidence: Absence from this document; the Implementation Manual and the Positive List of chemical inputs were not read.
Source: GOTS 8.1 (2026) Link to this fact
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
Many people with chemical sensitivities delay or avoid medical care because clinics and hospitals are heavily scented; healthcare was named as one of the least accessible settings (31 of 60).
Moderate evidence: Qualitative, self-selected Canadian sample; frequency of care avoidance not quantified.
Source: Roy 2026 Link to this fact
Health effects / Review of other studies
Fragrance can cause skin allergy without touching your own products: from a partner's toiletries (consort dermatitis), from soap residue carried on the hands to the eyelids, and through the air, as in a small case series of a ride-share driver and four passengers whose airborne facial/eyelid dermatitis (all patch-test positive for fragrance mix I and/or balsam of Peru) was linked to car fragrance diffusers, with the driver's rash clearing when his diffuser was removed.
Moderate evidence.
Caveats
Mechanisms from case reports and a systematic review of consort ACD cited by the review; the airborne example is now confirmed against its primary (Perper 2017, now ingested): actually 5 total patients (1 driver + 4 passengers), not just the driver, published in a Contact Dermatitis section the journal states is exempt from mandatory peer review, with no chemical/air testing, no controls, and diffuser-removal resolution documented only for the driver. Kept at moderate, not raised to strong, per the single-small-uncontrolled-study rule; no prevalence data.
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 / Lab study (cells or chemistry)
Three fragrance and cosmetic chemicals used in bodycare products applied around the breast, benzyl salicylate, benzyl benzoate, and butylphenylmethylpropional (Lilial), activated the human estrogen receptor and increased growth of estrogen-dependent breast cancer cells in a laboratory dish, an effect blocked by an anti-estrogen drug, suggesting the mechanism runs through the estrogen receptor.
Moderate evidence.
Caveats
Independent, non-industry-funded MCF7 cell study; concentrations required were 10,000 to 3,000,000-fold higher than the estradiol positive control, and none of the three compounds produced a full agonist response within 7 days (partial agonists at that timepoint, converging toward full over 35 days). No animal or human confirmation exists for any of the three compounds. A 2023 independent, guideline-validated retest of Lilial alone (OECD/EPA HeLa9903 ER-transactivation and MDA-kb2 AR-transactivation reporter assays, up to 100 µM, including its major Phase I S9 metabolites) found no estrogenic or androgenic agonist activity at all; this does not test benzyl salicylate or benzyl benzoate, and uses a different (receptor-transactivation vs. proliferation/pS2) endpoint, so it complicates but does not retract this finding for Lilial specifically.
Source: Charles & Darbre 2009, Journal of Applied Toxicology Link to this fact
Health effects / Measured in people or real products
Wearing a mask with an active-carbon filter, the kind designed to remove odors and organic vapors from the air, did not stop a scent-triggered breathing reaction to perfume: symptom scores with the carbon filter were no different from a dummy filter.
Moderate evidence.
Caveats
N=9, one perfume, unmeasured chamber concentration, single clinic; this arm of the study was double-blind. The paper's own hypothesis is that the reaction may enter through the eyes, which the mask does not cover, so this does not test filters that also shield the eyes.
Source: Millqvist & Löwhagen 1996, Allergy Link to this fact
Health effects / Measured in people or real products
In a small case series, an Uber driver and four Uber passengers developed facial and eyelid airborne contact dermatitis linked to fragrance diffusers used inside the cars; all five patients had positive patch tests to fragrance mix I and/or balsam of Peru, and the driver's dermatitis improved after he removed his own diffuser.
Moderate evidence.
Caveats
Only 5 patients from one clinic; published in the journal's 'Contact Points' section, which the journal states is exempt from mandatory peer review (editor review only); no chemical analysis of the diffusers, no air sampling, no control group; diffuser-removal resolution documented for the driver only, not the 4 passenger cases.
Source: Perper et al. 2017, Contact Dermatitis Link to this fact
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 / 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 / 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
In the same national survey, almost 1 in 3 adults (31.1%) said being next to someone wearing a scented product was irritating, and about 1 in 6 (17.6%) said air fresheners gave them headaches, breathing difficulties, or other health problems.
Moderate evidence.
Caveats
Self-report, single national telephone survey; 46.3% found scented products on others appealing rather than irritating. The same 2002-03 survey is re-reported as 17.5% (n=1,057) in Caress & Steinemann 2009 and as 17.8% in Steinemann 2009; quote 'about 1 in 6'.
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 / Other evidence
In a large Canadian population survey, more frequent use of personal care products was associated with small but statistically significant reductions in objectively measured lung function.
Moderate evidence: Single cross-sectional study; exposure was self-reported, not measured; cannot establish causation.
Source: Dales 2013, Annals of Epidemiology Link to this fact
Health effects / Other evidence
Restricting the analysis to never-smokers did not remove the association between personal care product use and lower lung function in women.
Moderate evidence: Subgroup analysis of a single cross-sectional cohort; wide confidence intervals.
Source: Dales 2013, Annals of Epidemiology 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
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 / Measured in people or real products
When candle emissions were converted to realistic household exposure (a 30 m3 room, candle burning 4 hours a day, 4 days a week), most measured pollutants (carbon monoxide, carbon dioxide, formaldehyde, PM2.5, benzene, most VOCs) stayed below international indoor air guide values, but nitrogen dioxide, acrolein, and benzo[a]pyrene exceeded some (not all) of the guide values tested, depending on which health agency's reference value was used.
Moderate evidence.
Caveats
Acrolein exceeded the US EPA reference concentration in all 8 experiments where it was quantifiable (compliance factor 1.3-6.3); benzo[a]pyrene exceeded the WHO guide value (factor 0.32-6.35) but not the more lenient US EPA reference concentration; nitrogen dioxide exceeded a precautionary German guide value but not the WHO/EU long-term value. Single chamber study; guide-value comparisons vary substantially by which agency's number is applied.
Source: Salthammer 2021, Environment International Industry-funded Link to this fact
Health effects / Review of other studies
Underarm body odor is mostly made by skin bacteria, not by sweat itself: apocrine-gland secretions are odorless when released, and only turn into the characteristic musk/urine smell after aerobic Corynebacteria metabolize odorless steroid precursors into 16-androstenes, or after bacteria break the goat-like acid 3-methyl-2-hexenoic acid free from its carrier proteins.
Moderate evidence: Review synthesis of older primary biochemistry literature, not this paper's own new data.
Source: Kippenberger 2012, Experimental Dermatology Link to this fact
Health effects / Review of other studies
Several metabolic and infectious diseases have documented, specific body-odor signatures: trimethylaminuria smells of rotten fish in urine/sweat/breath/saliva/semen, diabetic ketoacidosis smells of acetone, maple syrup urine disease smells of caramelized sugar, and typhoid fever produces a musty or fresh-baked-bread body odor.
Moderate evidence: Compiled from decades-old, mostly single case-series/case-report literature, not systematically re-verified by this review.
Source: Kippenberger 2012, Experimental Dermatology 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 / Measured in people or real products
Acetaldehyde, a probable human carcinogen, rose far more than its boiling point alone would predict once candles were lit — one strawberry candle's on/off concentration ratio for acetaldehyde was 3,688-fold, the largest ratio of any of the 34 compounds tracked in the study.
Moderate evidence.
Caveats
Acetaldehyde stayed far below the ACGIH/OSHA guideline values in absolute terms (max 640 ppb vs. 25,000/200,000 ppb guidelines); this finding is about combustion massively amplifying this one compound's relative output, not about it reaching a regulatory threshold.
Source: Ahn et al. 2015, Journal of Hazardous Materials Link to this fact
Health effects / Measured in people or real products
Kim et al. 2016 found their own original 2015 emission factors for carbonyl compounds from scented candles (formaldehyde and related aldehydes) had been computationally underestimated by exactly a factor of 250, due to a missed sample-dilution correction; the revised formaldehyde emission factor for the highest-emitting candle (SB-on) rose from 383 ng/g to 95.7 ug/g.
Moderate evidence: Single lab, self-corrected; independent replication of the corrected emission factors has not been reported.
Source: Kim et al. 2016, Journal of Hazardous Materials Link to this fact
Health effects / Measured in people or real products
A Korean government risk assessment of 64 deodorants found that at the maximum concentrations actually measured in the products, none of the 19 fragrance and biocidal ingredients carried to detailed (tiered 2) assessment exceeded its margin-of-exposure or hazard-quotient safety threshold, for either the inhalation or the dermal route.
Moderate evidence.
Caveats
A single government risk-assessment study using modeled Korean population-average exposure factors and mostly-animal (rat) toxicity reference values with standard uncertainty factors, not a clinical safety trial; not independently replicated.
Source: Kim et al. 2018, Science of The Total Environment Link to this fact
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 / Animal study
Scented candle fumes alone, at an occupational-intensity chamber dose, significantly increased inflammatory cytokines (TNF-alpha, IL-6, IL-1beta) and NF-kB activity in the lungs of mice, and caused measurable lung histological injury, without significantly raising heart inflammatory markers, heart NF-kB, cardiac injury markers (LDH, CPK, CKMB), plasma BNP, or heart HIF-1alpha above unexposed controls.
Moderate evidence.
Caveats
Single mouse study, N=8 per group, no independent replication; the candle-only lung effect is a within-study finding, but the same paper found no cardiac effect from candle fumes alone, so the finding is respiratory-specific in this model.
Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact
Health effects / Animal study
In mice, chronic social-disruption stress combined with scented candle fume exposure produced significantly worse cardiopulmonary inflammation and injury (BALF/lung/heart cytokines, NF-kB activity, serum LDH/CPK/CKMB, plasma BNP, heart HIF-1alpha, and lung histological injury) than either stress or candle fumes alone, though no group showed significant heart tissue histopathology.
Moderate evidence.
Caveats
Single lab, single mouse cohort (N=8/group), no independent replication; the stress model (repeated social defeat) and candle-fume dose are both occupational-intensity, so the additive effect size may not generalize to lower-intensity human exposures.
Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact
Health effects / Other evidence
Polycyclic aromatic hydrocarbons identified as carcinogens, including naphthalene, anthracene, and pyrene, have been found in candle fumes from wax, aroma substances or combustion dyes.
Moderate evidence: Directionally consistent with our own chamber PAH data (Salthammer 2021, Andersen 2021), though the editorial's own citation (Orecchio 2011) is not itself in this evidence base.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
Health effects / Test-chamber measurement
Scented candle fumes failed to reduce chronic-stress-induced serum corticosterone and instead increased inflammatory biomarkers, proinflammatory cytokine production, and NF-kB activation in the lungs and heart, causing cardiopulmonary injury.
Moderate evidence.
Caveats
Single-lab mouse study at an occupational-intensity chamber dose (already our own grading for this primary at C328); not a demonstration that candle scent itself fails to provide subjective psychological relief in humans.
Source: Singh 2023, Environmental Science & Technology Link to this fact
Health effects / Measured in people or real products
The estimated DEHP-attributable cardiovascular mortality burden falls hardest on the Middle East, South Asia, East Asia, and the Pacific, which together account for about 73% of all estimated DEHP-attributable deaths, while the USA and Europe show the lowest attributable share (about 10% and 8%).
Moderate evidence.
Caveats
Regional exposure estimates for Africa, Asia-EPA, Asia-MESA, Latin America, and Australia came from a meta-analysis/imputation model rather than direct national biomonitoring, so their precision is lower than the USA/Canada/Europe estimates, which used real biomonitoring surveys.
Health effects / Measured in people or real products
Countries with large aging populations and expanding plastics industries — India, China, and Indonesia — bear the largest absolute numbers of DEHP-attributable cardiovascular deaths in 2018 (about 104,000, 61,000 and 20,000 respectively).
Moderate evidence: Modeled estimate built on country-level population and mortality-rate data, not a direct count of deaths caused by DEHP.
Health effects / Government agency
IARC classifies benzophenone (CAS 119-61-9) as Group 2B, possibly carcinogenic to humans, based on sufficient evidence in experimental animals: dose-related liver tumors (hepatocellular adenoma, and rare hepatoblastoma) in male mice, histiocytic sarcoma in female mice, renal tubule adenoma in male rats, and mononuclear-cell leukemia in rats, from two 2-year NTP feed studies; no human cancer data exist on benzophenone.
Moderate evidence.
Caveats
Classification rests on animal bioassays only; IARC itself states no human data were available, and calls the mechanistic evidence for tumor induction 'weak' even while it cannot exclude human relevance.
Source: IARC 2013 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 / Animal study
Styrene-7,8-oxide, styrene's main metabolite, was separately classified by IARC in 2019 as Group 2A ("probably carcinogenic to humans") based on sufficient evidence in animals and strong mechanistic evidence that it is an electrophile which reacts directly with DNA and is genotoxic, even though human cancer evidence for styrene-7,8-oxide itself was rated "inadequate."
Moderate evidence.
Caveats
Human cancer evidence for styrene-7,8-oxide specifically (as opposed to styrene) was inadequate; the classification rests on animal bioassay and mechanistic/genotoxicity evidence, not human epidemiology.
Source: IARC 2019 (Vol. 121) Link to this fact
Health effects / Review of other studies
Formaldehyde, released by household cleaning products both directly and via reaction with indoor ozone, is described as a human carcinogen as well as a respiratory irritant.
Moderate evidence.
Caveats
This is a background descriptive statement in an emissions-chamber study, not new primary carcinogenicity data; it does not itself cite IARC or NTP classifications by name. Corroborated separately in our evidence base by US EPA's own indoor-air VOC guidance, which states plainly that benzene is 'a known human carcinogen' (src-2026-epa-voc-impact-indoor-air-quality) — so both halves of the video's statement (benzene and formaldehyde) are independently backed by evidence base source pages, though not yet as a combined graded claim.
Source: Rossignol 2013, Atmospheric Environment Link to this fact
Health effects / Measured in people or real products
Everyday background triclosan exposure (from sources other than labeled personal-care products, such as food, textiles, and footwear) is large and variable enough that, in this study, it obscured any clear difference between people who recently used triclosan-labeled toothpaste/soap and those who hadn't, once both groups had stopped using such products for 6 days.
Moderate evidence.
Caveats
Qualitative observation (no statistical test reported for this specific comparison); small sample (n=10, 5 vs 5); the authors themselves attribute the pattern to incomplete exposure monitoring rather than concluding product use has no effect.
Source: Sandborgh-Englund et al. 2006, Journal of Toxicology and Environmental Health, Part A Link to this fact
Health effects / Other evidence
Four cleaning occupations (unspecified cleaners, domestic helpers and cleaners, helpers/cleaners in offices and hotels, and hand-launderers) were associated with adult onset asthma in this cohort, with odds ratios from 1.58 to 2.26; the offices/hotels cleaning code (OR 1.82, 95% CI 1.34-2.48) and home-based personal care workers (OR 1.94, 95% CI 1.40-2.69) remained significant after correcting for testing 61 occupations.
Moderate evidence: Job-title-level exposure, not product-level; the lowest estimate (unspecified cleaners, OR 1.58) did not reach significance on its own (p=0.078).
Health effects / Other evidence
People who went on to develop adult onset asthma spent less time working in the jobs linked to asthma than people who did not develop asthma (e.g., home-based personal care workers: 1.88 years vs 3.18 years, p=0.016; domestic helpers and cleaners: 1.08 years vs 3.14 years, p=0.022), consistent with a 'healthy worker effect' in which people leave jobs that cause or worsen their disease.
Moderate evidence: This pattern supports the cohort's occupational associations being real rather than reverse-caused, but does not rule out all residual confounding.
Health effects / Self-reported survey
In a retrospective cohort of 1,010 tertiary-care migraine patients, premonitory symptoms (onset 2 or more hours before the headache) occurred in 38.5% (389/1,010), the most frequent being a tense neck, phonophobia, and difficulty concentrating; osmophobia as a premonitory symptom occurred in roughly a fifth of patients and was significantly more common in migraine with aura than without (p<0.05).
Moderate evidence.
Caveats
Retrospective design subject to recall bias; tertiary headache center sample likely more severely affected than the general migraine population; abstract states 38.9%, Results/Discussion body text states 38.5% — an internal inconsistency in the primary.
Source: Schulte 2015, The Journal of Headache and Pain Link to this fact
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 / Other evidence
The authors concluded the clinical effects seen in homeopathy trials are compatible with placebo and context effects, and that future research should address those context effects and homeopathy's place in health care instead of more placebo-controlled trials.
Moderate evidence: Authors' interpretation; they state that proving a negative is impossible and that the study addressed only specific remedy effects.
Health effects / Other evidence
The 'water memory' explanation for homeopathy is at odds with measurements: hydrogen bonds in liquid water rearrange in under about 50 femtoseconds, far too briefly to carry the identity of a diluted substance.
Moderate evidence: Relies on one cited experiment; the paper does not review the wider water-structure literature, and proponents dispute the relevance of such time scales.
Source: Grimes 2012, Focus Altern Complement Ther, Focus on Alternative and Complementary Therapies Link to this fact
Health effects / Review of other studies
A 2016 review of professional clothing-cleaning methods reports that perchloroethylene (perc), the most widely used dry-cleaning solvent, is classed by the International Agency for Research on Cancer as probably carcinogenic to humans (group 2A), with kidney cancer, liver cancer, and non-Hodgkin lymphoma among the cancers linked to it in workers or residents.
Moderate evidence.
Caveats
Secondary review funded by Australian Wool Innovation (wool industry body); 'systematic' is a self-label with no study counts or appraisal; relies on agency, trade and manufacturer sources. The review restates other studies' findings; it contains no new exposure or outcome data, and the IARC class is a hazard rating, not a risk estimate for wearing dry-cleaned clothes.
Source: Troynikov 2016, Journal of Environmental Management Industry-funded Link to this fact
Health effects / Measured in people or real products
In the same study, the low-molecular-weight phthalate group, which includes diethyl phthalate (DEP), the phthalate used in fragrance and personal care, showed no all-cause mortality signal (continuous HR 1.01, 0.96-1.07; top third vs bottom third 1.11, 0.91-1.34).
Moderate evidence.
Caveats
A null result in one cohort using single spot-urine samples; the pooled group also includes other phthalates, and the top tertile of the DEP metabolite MEP was linked to cardiovascular death (HR 1.64, 1.07-2.51) but not in the continuous model.
Source: Trasande, Liu & Bao 2022, Environmental Pollution Link to this fact
Health effects / Other evidence
The US National Toxicology Program found 'clear evidence' that isoeugenol caused liver tumors in male mice (combined adenoma or carcinoma in 43 of 50 at each dose versus 28 of 50 in controls) and 'equivocal evidence' in male rats and female mice; the flavor panel judged this irrelevant to people at flavor intake.
Moderate evidence.
Caveats
Numbers are the panel's quotation of an NTP draft report; the panel's dismissal (high control tumor rate, hepatotoxicity) is the industry position, and its margin arithmetic contains a 750-fold versus 'six orders' inconsistency.
Source: Smith et al. 2009 (FEMA Expert Panel), GRAS Flavoring Substances 24, Food Technology 63(6), Food Technology Industry-funded Link to this fact
Health effects / Self-reported survey
In two US national telephone surveys, about 1 in 5 adults said air fresheners or deodorizers give them headaches, breathing difficulties, or other problems: 17.5% in 2002-03 and 20.5% in 2005-06 (19.0% averaged).
Moderate evidence.
Caveats
Self-report; the two values are within each sample's stated plus or minus 3% precision, so the rise is borderline. An earlier paper by the same author quotes 17.8% for the first survey, and the sister 2003 paper prints 17.6%.
Source: Caress & Steinemann 2009, Journal of Environmental Health 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
Women reported fragrance reactions more often than men in both national surveys: others' scent irritating 36.0% vs 22.5% (2002-03) and 31.6% vs 27.0% (2005-06); air-freshener problems 21.1% vs 11.4% and 22.0% vs 17.7%.
Moderate evidence: Self-report; reporting differences are not the same as biological differences; later surveys show a smaller sex gap on some items.
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 / Other evidence
The US National Toxicology Program reported 'clear evidence of carcinogenic activity' of pyridine (a flavor and food constituent) in male and female mice, with liver carcinoma in males 15/50 (control) vs 35/50, 41/49, and 40/50 across three doses and hepatoblastoma in females 1/49 vs 2/50, 9/50, and 16/50, and 'some evidence' in male rats (kidney adenoma 2/50 vs 10/50 at the top dose).
Moderate evidence.
Caveats
Rodent bioassay (2-year, drinking water), numbers quoted by the industry panel from NTP 2000, not the NTP report itself; mouse liver tumors in B6C3F1 are known to have high background rates.
Source: FEMA GRAS 25 (2011), Food Technology Industry-funded Link to this fact
Health effects / Other evidence
The panel's 2024 evaluation criterion for flavor oils containing genotoxic-carcinogen constituents (safrole, estragole, methyl eugenol, myristicin) is a margin of exposure of 10,000, with a 0.15 microgram per person per day threshold as the first screen.
Moderate evidence: The panel states the benchmark matches EFSA and JECFA; the intake inputs are industry-derived.
Source: FEMA Expert Panel 2024 (GRAS 31), Food Technology Industry-funded Link to this fact
Health effects / Other evidence
In a Puerto Rico pregnancy cohort, urinary benzophenone-3, triclosan, and parabens averaged two to three times higher after recent lotion use, benzophenone-3 about fivefold higher after sunscreen use, and triclosan and triclocarban two- and fourfold higher with liquid and bar soap use (EWG's relay).
Moderate evidence: Secondhand numbers; the page gives no authors or DOI; exposure biomarkers are not health outcomes.
Source: EWG 2025 (Friedman & Huang), EWG news (web page) Link to this fact
Information, not medical advice. See also: myths we won’t tell you.