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.
Fragrance is everywhere / Other evidence
Shopping malls can diffuse a scent blend through their common areas, installed by a professional scent-marketing agency, so every visitor is exposed without any way to opt out; the mall studied used orange, grapefruit, bergamot, cinnamon, cardamom, ginger, and pimento 'and other additives'.
Weak evidence: A single research mall; no concentration or full composition was reported, and the paper makes no health or allergen claim.
Source: Teller 2012, Journal of Marketing Management Link to this fact
Fragrance is everywhere / Other evidence
Within New York City buildings that housed a perchloroethylene dry cleaner, low-income households (under $30,000) had mean indoor air of about 105 micrograms per cubic meter versus about 18 in households earning over $60,000, roughly six times higher; adults' mean blood levels were 0.62 versus 0.14 ng/mL.
Weak evidence.
Caveats
Small cells (17 vs 30 households for air); the authors report the stratified differences in air, breath and blood were not statistically significant; sample weighted toward minority, low-income and complaint buildings; the explanation (housing conditions) is the authors' inference.
Source: Storm 2013, Environmental Research Link to this fact
Fragrance is everywhere / Other evidence
In the same study, minority households in dry-cleaner buildings had mean indoor air of about 82 micrograms per cubic meter versus about 17 for non-minority households (about five times), and minority children's mean blood level was 0.27 versus 0.12 ng/mL.
Weak evidence: Stratified differences not statistically significant; 26 vs 31 households for air, 17 vs 21 children for blood; building selection weighted toward minority and low-income areas.
Source: Storm 2013, Environmental Research Link to this fact
Fragrance is everywhere / Other evidence
In New York City buildings without a dry cleaner, higher-income adults had slightly higher blood perchloroethylene than lower-income adults (0.06 versus 0.03 ng/mL) despite equal indoor air; the authors suggest this reflects more dry-cleaned clothes at home (97% of higher-income versus 47% of lower-income households brought them home).
Weak evidence.
Caveats
The clothing explanation is an inference from a questionnaire answered by 71 participants; clothing exposure was not measured; levels are near background and the authors know of no health effect.
Source: Storm 2013, Environmental Research Link to this fact
Fragrance is everywhere / Other evidence
In the industry's illustrative model of 36,446 US and European adults, the 95th-percentile person received about 7.55 g/day of product on the skin and in the mouth from 19 personal-care product types, with mouthwash, mass-market body lotion, and deodorant roll-on the largest contributors.
Weak evidence: Model output from 2007-2008 diary data, industry-funded; Fig. 3 shares are read from a chart.
Source: Safford et al. 2015, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Fragrance is everywhere / Other evidence
In a lab, people in a cinnamon-scented room judged it more crowded and cool-scent participants underestimated the head count, showing a pleasant scent can bias how a space is perceived without being identified (only 4 to 6% named the scent).
Weak evidence: University students (n = 113), one lab, scent concentration not reported; cinnamon vs peppermint contrast only, no unscented control in the pilot.
Source: Madzharov 2015, Journal of Marketing Link to this fact
Fragrance is everywhere / Other evidence
After spraying a car air freshener, benzene and several other aromatic VOCs measured in the cabin went down by an average of about 40% for benzene (except in recirculation mode) while limonene went up, so the product masks rather than removes the car's own chemicals.
Weak evidence: The sprays contained no benzene; the drop was transient, came with no unsprayed control, and the authors' masking/displacement explanation was not tested.
Source: Lee 2024, Science of The Total Environment Link to this fact
Fragrance is everywhere / Measured in people or real products
Chlorine bleach cleaners emitted chloroform and methylene chloride in the chamber; the authors say it was not determined whether these were in the product or formed in the chamber, and that the chamber likely underestimates real-world bleach by-products.
Weak evidence.
Caveats
EWG-authored (advocacy nonprofit that ranks cleaners and licenses EWG VERIFIED to cleaner makers); Skyline Foundation grant; unblinded; Two bleach products; origin of the chlorinated compounds untested.
Fragrance is everywhere / Other evidence
Flavor GRAS evaluation covers eating only: the 2024 list gives food-category use levels in ppm and nothing on inhalation or skin, though several listed materials (nutmeg, mace, basil, parsley, patchouli, nootkatone) are also fragrance materials.
Weak evidence: Absence of inhalation discussion in this short list; the panel's own earlier papers state the gap more directly.
Source: FEMA Expert Panel 2024 (GRAS 31), Food Technology Industry-funded Link to this fact
Fragrance is everywhere / Other evidence
Skin Deep's product scores are not an average of ingredient scores: EWG says it adds weight for skin-penetration enhancers and for combinations of ingredients tied to many health concerns, but it publishes no formula on this page.
Weak evidence: Method described in words only; the weights are not given here.
Source: EWG, Skin Deep FAQ (web page, accessed 2026-10-16), EWG web page (Skin Deep FAQ) Link to this fact
Fragrance is everywhere / Government agency
Alpha-isomethyl ionone, an allergen on the EU's 1999 labeled list, was declared on 46.6% of 88 deodorants checked in 2007 and detected in about 65% of 23 analyzed deodorants (6-2,588 ppm); it was found in 21.7% of 516 consumer products in another survey.
Weak evidence.
Caveats
Small, older market surveys cited from other authors (German/Danish samples); label-declaration frequency, not exposure; the underlying patch-test rates for this chemical are low (0-2.1%).
Fragrance is everywhere / Other evidence
Less volatile fragrance compounds (linalool, geraniol, eugenol, ethylene brassylate) moved onto a second fabric far more readily than the volatile terpenes pinene and limonene.
Weak evidence: Recoveries are percentages of a reference swatch for six compounds in a lab model; roughly 15-35% vs about 0.5-1% in the contact-time experiment.
Fragrance is everywhere / Other evidence
Cotton and polyester recipient fabrics took up the same fragrance mixture differently enough to be told apart statistically.
Weak evidence: One small lab experiment with multivariate models on six compounds; no per-compound fabric ranking reported.
Fragrance is everywhere / Other evidence
Four of six fragrance compounds could still be measured on cotton and polyester 28 days after transfer, but the two lightest citrus and pine terpenes (limonene, alpha-pinene) could not be quantified at room temperature.
Weak evidence: Detectability by sensitive GC-MS in a spiked-standard bench model, n = 3; says nothing about amounts that matter to health.
Fragrance is everywhere / Other evidence
A synthetic musk (ethylene brassylate) was the most persistent fragrance compound tested on cotton, with about 335 µM/g still on the fabric at 14 days versus about 535 µM/g at 1 hour.
Weak evidence: Irregular trend (a spike at 5 d), large standard deviations (±57 to ±109), one spiked mixture, n = 3. Polyester held far less (about 43 µM/g at 14 d).
Fragrance is everywhere / Other evidence
CTV reported a 2014 survey finding about 2.4 per cent of Canadians (more than 770,000) have been diagnosed by a health-care provider with MCS.
Weak evidence: CTV does not name the survey; primary source not checked here. Do not repeat as established until the primary is found.
Source: CTV News, April 2022 (via Smoke-Free Housing BC; redacted copy), CTV News (news article) Link to this fact
Fragrance is everywhere / Other evidence
In the French cohort of about 3,000 children discussed in the review, maternal occupational solvent exposure in pregnancy was associated with dose-related increases in hyperactivity and aggression at age 2, and one in five mothers reported solvent exposure in common jobs including nurse, cleaner, hairdresser and beautician.
Weak evidence: Occupational solvents as a class, with no individual compound identified; it says nothing about perfume or fragrance exposure at home.
Source: Grandjean & Landrigan 2014, Lancet Neurology, The Lancet Neurology Link to this fact
Fragrance is everywhere / Review of other studies
The review lists perfumes, hair sprays, soaps and nail varnishes as products that contain phthalates, but names no specific phthalate for those products and no musk, UV filter, paraben or terpene.
Weak evidence: One generic sentence; it supports no fragrance-specific neurotoxicity claim.
Source: Jocsak 2026, Frontiers in Behavioral Neuroscience Link to this fact
Fragrance is everywhere / Other evidence
In a 30-person Shanghai lab study, a floral-musk perfume blend from Shiseido (jasmine, musk, muguet, rose, bergamot and others) was linked to faster reaction times on a go/nogo button task after a 15-minute simulated drive (about 445 ms vs 484 ms with no scent).
Weak evidence.
Caveats
Small crossover, young adults, nobody drove (watched a video), participants could smell the scent so it was not blinded, odorless rather than placebo-odor control, no air concentration measured, scent supplier employed the first author, and stats treat paired data as independent.
Fragrance is everywhere / Other evidence
The same study found no scent effect on the oddball task, and the Stroop task got faster with and without the scent (about 32 ms with, about 47 ms without), which the authors attribute to learning.
Weak evidence: Small crossover study; the two conditions also differed at baseline on Stroop and go/nogo, which complicates comparison.
Fragrance is everywhere / Other evidence
Despite the abstract's claim of EEG support, only one of four EEG measures (prefrontal theta, about 3.0 vs 1.9 z-score) differed between scent and no-scent; beta waves and the fatigue index did not.
Weak evidence: Reported statistics are unusual (F(1,4), F=2.601 with p=.015); theta is read by the authors both as relaxation and fatigue; one small study.
Fragrance is everywhere / Other evidence
Parent-reported US ADHD diagnosis in 2022 (11.4%) was higher than in 2016 (9.9%), but the survey's weighting and imputation methods changed in 2022, and the authors list awareness, pandemic stress and schooling as possible reasons without testing them.
Weak evidence: A rise in reported diagnosis is not a rise in the trait and not evidence of an environmental cause; the 2016-2021 NSCH trend (Leeb 2024) was not statistically significant.
Source: Danielson 2024 (NSCH 2022), Journal of Clinical Child & Adolescent Psychology Link to this fact
Green, natural and unscented / Measured in people or real products
Scented tampons carried a median of 692 ng/g of fragrance terpenes against 2.9 ng/g in unscented ones.
Weak evidence: Only 2 scented vs 20 unscented tampons (p=0.04).
Source: Lin 2020, Environment International Link to this fact
Green, natural and unscented / Government agency
Under EU/UK law, a 'free from [substance]' cosmetic claim about a substance already banned for all EU cosmetics would appear to fall under the rule barring claims that dress up mere legal compliance as a special product benefit.
Weak evidence.
Caveats
This is our own reading of the regulation's general Criterion 1(3) applied to 'free from' wording, not a quotation naming that claim type, and no enforcement decision confirming this application was found.
Source: Commission Regulation (EU) No 655/2013 Link to this fact
Green, natural and unscented / Self-reported survey
'Fragrance-free'/'unscented' deodorant claims are not a reliable guarantee for fragrance-allergic people: in a cited patient survey, 4.7% of fragrance-contact-allergic patients who had used an unscented deodorant in the past 3 months got a rash from it.
Weak evidence: Figure is relayed from Lysdal and Johansen 2009, not Klaschka's own data; not in our evidence base as a primary yet.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
Green, natural and unscented / Lab study (cells or chemistry)
A cold-atmospheric-plasma prototype device killed over 90% of two underarm-odor bacteria (Staphylococcus hominis 99.81%, Corynebacterium xerosis 90.99%) after 3 minutes of exposure in lab culture, and cut total electronic-nose sensor response to two major axillary-odor chemicals by about 51% (HMHA) and 34% (3M3SH) after 5 minutes, without applying antimicrobial chemicals or fragrance to skin.
Weak evidence.
Caveats
Antibacterial test used agar-cultured bacteria; deodorizing test used excised porcine skin dosed with pure synthetic odor compounds in methanol, not human sweat. Single lab, single prototype, no independent replication, no human skin testing.
Source: Bok et al. 2024, Scientific Reports Link to this fact
Green, natural and unscented / Other evidence
Candles made from renewable waxes (beeswax, soy, coconut, palm) scented with natural essential oils are generally safer and more sustainable than paraffin candles, but still carry an environmental cost through deforestation and habitat destruction from increased crop demand.
Weak evidence.
Caveats
No emissions or land-use quantification given; our own chamber data (Salthammer 2021, Andersen 2021) also show wax type has little effect on formaldehyde/PAH output compared to fragrance load, so a wax switch alone may not reduce indoor-air health risk even if it changes the environmental footprint.
Source: Singh 2023, Environmental Science & Technology Link to this fact
Green, natural and unscented / Other evidence
Study participants were given a free 'starter kit' of unscented cleaning products and 'alternative cleaning recipes' as part of a personalized action plan to reduce indoor VOC exposure, and researchers observed reduced use of scented products at follow-up visits.
Weak evidence.
Caveats
Product-use reduction was assessed by researcher observation during a scheduled visit, not by continuous monitoring, and patients knew they were being evaluated (compliance may be overstated).
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Green, natural and unscented / Measured in people or real products
Two 'green' products still had a formaldehyde hazard quotient above 1 in the chamber test, and the 'green' air freshener emitted about as much per spray (3,210 vs 3,803 ug) as the conventional one; green did not mean no hazardous emissions.
Weak evidence.
Caveats
EWG-authored (advocacy nonprofit that ranks cleaners and licenses EWG VERIFIED to cleaner makers); Skyline Foundation grant; unblinded; Two products and two air fresheners only; formaldehyde limit is very low so small amounts drive the index; ISO 16000-3 carbonyl method.
Green, natural and unscented / Other evidence
EWG found that 'green' marketing did not predict ingredient disclosure: some leading green brands rated highly, while others, including Earth Friendly Products and BabyGanics, did not disclose ingredients adequately.
Weak evidence: Brand-level statements by an advocacy group; the grades behind them are not shown on this page and may have changed.
Source: EWG press release, Sept. 10, 2012, EWG press release (web page) Link to this fact
Green, natural and unscented / Other evidence
63.3% of surveyed UAE women said they preferred fragrance-free products when available, while 82.2% believed natural ingredients are healthier.
Weak evidence: Open-link snowball sample of 461 women, mostly young and university-educated; self-report, no exposure measurement; not weighted, so not a UAE prevalence.
Source: AlBlooshi 2026, Frontiers in Toxicology Link to this fact
Green, natural and unscented / Test-chamber measurement
The limonene given off by a natural fragrant plant is the same chemical as the limonene in cleaners and air fresheners; in this study three plants took room limonene to about 60-84 ug/m3 on average over 3 hours, in the range of a plug-in air freshener and well below the 1,000-6,000 ug/m3 seen right after terpene cleaning in a chamber.
Weak evidence: Cross-study comparison of different averaging times and rooms; the 'after' means are back-calculated from the dose table; plug-in and cleaning values come from other studies.
Health effects / Review of other studies
A 2022 review concluded that links between contaminants in perfumes and cancer, breathing problems, and hormone disruption are 'probable' but still need research to prove.
Weak evidence: Evidence mostly from phthalate/paraben studies not perfume exposure.
Source: Kazemi 2022, Journal of Environmental Health Science and Engineering Link to this fact
Health effects / Lab study (cells or chemistry)
In lab tests on cancer-derived nerve cell lines, three unnamed commercial fragrances changed cell shape and structure after 72 hours and cut the share of cells carrying oxytocin and vasopressin receptors in some lines but not others.
Weak evidence: Cell lines only; fragrances unidentified; no replication; only one cell line per sex.
Source: Sealey 2015, Environmental Research Link to this fact
Health effects / Hypothesis
Silent Spring Institute researchers name house cleaners and nurses as priority jobs for cutting exposure to fragrance, cleaning, and personal-care chemicals linked to breast cancer in lab and animal studies.
Weak evidence: No exposure or cancer data in these workers.
Source: Knox 2026, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Health effects / Review of other studies
Many everyday chemicals, including some released by scented and cleaning products, act on the same irritant-sensor nerves in the nose and airways (TRPA1 and TRPV1), one reason very different products can cause similar symptoms.
Weak evidence: Mechanism largely from lab/animal studies; dose relevance to homes untested.
Source: Molot 2023, Neuroscience and Biobehavioral Reviews Link to this fact
Health effects / Animal study
In animal and lab studies, common scent chemicals such as linalool, limonene, and eugenol act on brain signaling systems; what lifelong low-level exposure does in healthy people has never been studied.
Weak evidence: Mostly high-dose animal/in-vitro pharmacology; often protective effects in disease models.
Source: Pinkas 2017, Environmental Research Link to this fact
Health effects / Lab study (cells or chemistry)
In lab studies, inflammation lowers the threshold for this irritant receptor, a proposed reason scent reactions can be worse when airways are already inflamed.
Weak evidence: Mechanistic pathway only; not demonstrated in people exposed to products.
Source: Mihara & Shibamoto 2015, Allergy, Asthma & Clinical Immunology Link to this fact
Health effects / Measured in people or real products
Two German gas-works plumbers who repeatedly hand-poured the gas odorant tetrahydrothiophene in an unventilated room developed chronic rhinitis and lasting airway obstruction; neither had allergies on skin testing, and the accident insurer accepted both as occupational disease.
Weak evidence: Two case reports; exposure estimated, not measured; one worker smoked ~16 pack-years; industrial odorant, not fragrance.
Source: Baur & Bittner 2009, American Journal of Industrial Medicine Link to this fact
Health effects / Lab study (cells or chemistry)
Musk ketone does not damage DNA by itself, but in rat liver enzymes and human liver cells it made known carcinogens like benzo[a]pyrene more mutagenic.
Weak evidence: One laboratory's data (the review's senior author); human-cell LOEL 50 ng/ml is 12-70x above whole-milk levels.
Source: Schmeiser 2001, International Journal of Hygiene and Environmental Health Link to this fact
Health effects / Animal study
In two of the five products the airflow reduction kept worsening after the exposure ended.
Weak evidence.
Caveats
Mice, n=3-12 per time course; no human counterpart; mechanism unknown. An independent replication attempt (Tepper et al. 1995, carpets, full text now in our evidence base) found no significant carpet-related toxicity overall via individual-animal statistics, but it never measured airflow limitation or post-exposure persistence of any respiratory endpoint, so it does not directly test this finding either way.
Source: Anderson & Anderson 1998, Archives of Environmental Health Link to this fact
Health effects / Review of other studies
Frequent private use of household disinfectants (a composite of methods including hand-wash, machine, sponge, and spray disinfection) was linked to close to a threefold increase in the odds of newly developing asthma in a single cross-sectional wave of young German adults (Weinmann 2017, OR 2.79, 95% CI 1.14-6.83); the evidence for household sprays alone driving that same result was already weak in that wave (OR 2.79, 95% CI 0.84-9.20), and a 10-year longitudinal follow-up of the same cohort (Pacheco Da Silva 2025) found no significant association between persistent spray-only use and current asthma or wheeze (point estimates at or below 1.0 for every outcome), with only a non-significant, attenuated OR of 1.68 (95% CI 0.48-5.88) for sustained use of multiple disinfectants/cleaning products together.
Weak evidence.
Caveats
Two analyses of the same German SOLAR cohort (Weinmann 2017's cross-sectional SOLAR II wave, and Pacheco Da Silva 2025's 10-year longitudinal follow-up adding SOLAR III with latent-class exposure profiles) now agree that spray-specific use is not significantly associated with adult asthma. The only positive signal across both papers is a composite 'persistent use of multiple DCPs' profile, which itself weakened from a significant OR 2.79 (single wave, simple frequency composite) to a non-significant OR 1.68 (10-year follow-up, latent-class model, wide CI 0.48-5.88). Both papers are single-cohort, self-reported-exposure studies from the same research group, so per the grading rule this stays below moderate. The follow-up nulls are underpowered (1,143 of the original 2,051; only ~8-12% in each persistent-use profile; CIs span roughly 0.5-6), so they weaken the claim without refuting it. Other cohorts not yet in our evidence base reported positive spray-asthma associations (ECRHS, Zock 2007; French EGEA, Pacheco Da Silva 2023); don't cite this cohort as evidence that sprays are safe.
Source: Salonen 2024, Environment International Link to this fact
Health effects / Review of other studies
Doctors have published detailed reports of 12 young children (8 boys, 4 girls) whose breasts began to grow while they used lavender or tea tree oil products such as colognes, baby bath soap, or hair gel; in every case the growth went away within months of stopping.
Weak evidence: Case reports only; no rechallenge; this kind of breast growth often regresses on its own; the review itself concludes causation is not shown.
Source: Braunstein & Braunstein 2023, touchREVIEWS in Endocrinology Industry-funded Link to this fact
Health effects / Lab study (cells or chemistry)
In human adrenal cells, eight common fragrance terpenes, eucalyptol, geraniol, carvone, 3-carene, ocimene, both pinenes, and dihydro-beta-ionone, cut production of the androgen precursor DHEA by 13–31%, and six others cut the activity of aromatase, the enzyme that makes estrogen, by 22–33%.
Weak evidence.
Caveats
Single 10 µM concentration, ~140–200× above what indoor air or ordinary product use could produce internally; the mass-spectrometry check was non-significant for eucalyptol (p = 0.0574) and null for dihydro-beta-ionone; the same 10 µM killed up to 50% of a prostate-cancer cell line by 48 h. Always state the concentration.
Health effects / Lab study (cells or chemistry)
In a lab-grown 3D model of human skin, polystyrene fragments up to 10 µm were cytotoxic and inflammatory in keratinocytes, but only the fragments 2 µm or smaller penetrated into the dermis (average maximum 4.7 µg) within an hour, switching on inflammation genes there.
Weak evidence.
Caveats
One 3D skin model study (Song 2024); independently read the same way by a second review (Menichetti et al. 2025, J Xenobiot), which also reports the <2 µm penetrating cutoff and notes that in ex vivo human and mouse skin from the same primary study, the cutoff for any penetration was stricter still, under 1 µm. Not intact living human skin; no real-use dose.
Health effects / Lab study (cells or chemistry)
Many perfumes contain strongly antibacterial compounds: activity against Gram-negative bacteria appeared at 50 billionths of a liter, and a single spray is about 2,000 times that amount.
Weak evidence: Plate assay with a marine bacterium; effect on the skin microbiome inferred by the authors, not tested.
Source: Morlock & Heil 2025, Journal of Chromatography A Link to this fact
Health effects / Measured in people or real products
In the same test, patients rated breathlessness and cough higher after perfume at the eyes (1.5 vs 0.4 and 0.9 vs 0.3 on a 0-3 scale), yet lung function, oxygen saturation, and breathing rate did not change at all.
Weak evidence: Single-blind (scorers apparently not blinded), 3 of many symptoms analyzed, n=11; the airway symptoms did not replicate double-blind (Elberling 2006: 6/11 perfume vs 5/11 placebo).
Health effects / Lab study (cells or chemistry)
A small 2026 follow-up study found mutagenic and cell-killing compounds in 8 perfumes, consistent with an earlier 42-perfume finding from the same German lab.
Weak evidence.
Caveats
Same lab and platform as the earlier study, not independent; only 8 unnamed perfumes, unclear overlap with the 42; simulated liver metabolism was built for this paper but explicitly not tested on the perfumes; no antibacterial or hormone-related endpoints were run.
Source: Schmidtmann 2026, Analytical Chemistry Link to this fact
Health effects / Measured in people or real products
A small clinic study found that a real cologne challenge produced an objective, reproducible 18-58% drop in FEV1 (lung function) within minutes in asthma patients who already reported cologne sensitivity, blocked mostly by bronchodilators rather than cromolyn or blocking the sense of smell.
Weak evidence: N=4 evaluable patients, unblinded first exposure, cologne dose never measured, single cologne brand, all pre-selected for a cologne-sensitivity history, 1986, unreplicated.
Source: Shim & Williams 1986, The American Journal of Medicine Link to this fact
Health effects / Measured in people or real products
Pleasant fragrance smells can measurably calm the body (raising a marker of parasympathetic "rest and digest" activity by up to 47% for pine scent and 26% for citrus), but once that same citrus scent has reacted with ozone, the calming effect reverses into a small drop in that same marker.
Weak evidence.
Caveats
Each condition (pure pine, pure citrus, and the ozone-reacted citrus mixture) comes from a separate, small study, not one head-to-head design; the review's own authors suggest perceived unpleasantness of the reacted mixture, not necessarily toxicity, may explain the reversal.
Source: Wolkoff & Nielsen 2017, Environment International Link to this fact
Health effects / Self-reported survey
In a 10-year longitudinal follow-up of a German young-adult cohort (SOLAR, n=1,143), only participants who persistently used multiple disinfectants and cleaning products (sprays, disinfectant sprays, and nonspray disinfection methods) weekly at two assessments 10 years apart showed an elevated point estimate for current asthma (OR 1.68) and current wheeze (OR 1.71) compared with no weekly use; neither reached statistical significance (95% CI 0.48-5.88 and 0.75-3.90).
Weak evidence.
Caveats
Same underlying cohort as Weinmann 2017 (SOLAR 2 exposure data reused); small persistent-use subgroup (8.2% of n=1,143); wide confidence intervals; incident-asthma/wheeze estimates too imprecise for inference; authors draw no causal conclusion.
Health effects / Animal study
When the air freshener's emissions were combined with fresh latex-paint emissions, the mixture was not less toxic in mice than paint alone — the behavioral (FOB) score rose further and significantly, countering claims that air fresheners neutralize or mask other indoor pollutants.
Weak evidence: Single product, single co-pollutant, one dose combination, mouse behavioral scoring only; not tested with other pollutant classes or in humans.
Source: Anderson & Anderson 1997, Archives of Environmental Health Link to this fact
Health effects / Other evidence
California state scientists estimate that cosmetics may account for at least 4% (and plausibly much more, given wide uncertainty) of the PFOA-related chemicals measured in San Francisco Bay Area wastewater.
Weak evidence.
Caveats
The comparison spans a very wide range (roughly 4% to several hundred percent of the median measured loading) because of unreliable use-concentration inputs; this is an environmental-loading estimate, not a personal health-exposure estimate.
Source: Balan 2024, Environmental Science & Technology Link to this fact
Health effects / Animal study
In ex vivo real human and mouse skin (not a lab-grown skin model), plastic nanoparticles only penetrated when they were smaller than about 1 micrometer, and human skin let slightly more through than mouse skin at that size, likely because human hair follicles are larger.
Weak evidence: Single primary study (Song et al. 2024) as read by this review; ex vivo excised tissue, not living skin measured during real use; no real-use cosmetic dose.
Source: Menichetti et al. 2025, Journal of Xenobiotics Link to this fact
Health effects / Measured in people or real products
Almost half (44%) of patients in the founding irritable larynx syndrome series related their symptom onset to a viral illness, most often not a simple upper respiratory infection but herpes zoster, Epstein-Barr virus, viral meningitis, Lyme disease, or post-viral chronic fatigue syndrome.
Weak evidence.
Caveats
Retrospective patient-recalled association, not confirmed causally; n=39, one clinic; the paper's own abstract says "one third", which its own Results text ("almost half") and Table 4 (17/39=43.6%) contradict.
Health effects / Review of other studies
Citronella oil, marketed as a natural insect repellent, has been banned in the European Union and Canada since 2006, partly because it contains methyl eugenol, which the US National Toxicology Program considers 'reasonably anticipated to be a human carcinogen' based on animal studies.
Weak evidence.
Caveats
No human carcinogenicity data exist for methyl eugenol; this is a regulatory ban and an animal-based NTP classification relayed by a secondary review, not measured harm from using citronella products.
Source: Ramsey 2020 (YJBM), Yale Journal of Biology and Medicine Link to this fact
Health effects / Review of other studies
No published study has been found that tests whether quaternary ammonium compounds specifically from laundry fabric softeners or dryer sheets, as opposed to disinfectant or cosmetic-preservative exposure, cause asthma or skin sensitization in consumers.
Weak evidence: This is an evidence-gap statement, not a positive finding; the review also never discusses esterquats, the ester-linked chemistry that dominates modern fabric softeners, at all.
Source: Peyneau 2022, Frontiers in Toxicology Link to this fact
Health effects / Review of other studies
Estimated prevalence of multiple chemical sensitivity across the reviewed epidemiological literature ranges from about 1% to more than 15% of the population, a spread the review attributes to diagnostic difficulty, lack of standardized case-definition criteria, and differing recognition of the condition across countries.
Weak evidence.
Caveats
Secondhand synthesis of several distinct primary studies with different case definitions and populations, not a single standardized measurement; the review does not report the underlying studies' individual case definitions in enough detail to weight the range.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Review of other studies
A cohort of laborers acutely exposed to gasoline vapors above allowed limits during an underground tunnel-excavation job later developed symptoms similar to those reported in multiple chemical sensitivity, and the study authors argued the workers' sociocultural profile made simple psychosomatic suggestibility an unlikely sole explanation.
Weak evidence.
Caveats
Cited secondhand from Davidoff et al. (primary study not yet in our evidence base); occupational cohort with no independent control for pre-existing chemical sensitivity, and "unlikely to be suggestible" is the original authors' qualitative judgment, not a tested exclusion of a psychological contribution.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Health effects / Review of other studies
Some solvents can theoretically sensitize the heart muscle to the body's own adrenaline-type hormones, raising a theoretical risk of arrhythmia or cardiac arrest under chemical exposure in people with multiple chemical sensitivity.
Weak evidence.
Caveats
Cited from a toxicology reference textbook (Olson, Acute Intoxications, Poisons, Pharmaceutical Substances and Drugs), not from any MCS-specific study; the review's own authors state this risk "has not been detected in any epidemiological study so far." Mechanistic/theoretical only.
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Information, not medical advice. See also: myths we won’t tell you.