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.
What you can do / Measured in people or real products
Screening out products whose labels list 'fragrance' and a few other terms cut synthetic fragrance: 26 of 43 screened products had no detectable fragrance chemical, and high fragrance levels appeared 21 times in conventional samples vs 2 in screened ones.
Moderate evidence: Conventional composites vs single alternatives not directly comparable; did not remove parabens, phthalate substitutes.
Source: Dodson 2012, Environmental Health Perspectives Link to this fact
What you can do / Measured in people or real products
Green, organic, or natural labels on baby products did not mean fewer released chemicals, so choosing products labeled fragrance-free (without essential oils) is the more reliable way to avoid scent chemicals.
Moderate evidence.
Caveats
Fragrance-free products were not tested directly for VOC emissions in Nematollahi 2018 (its own scope); Temkin 2023 (EWG-authored; unblinded chamber test of 30 US cleaners, 7 fragrance-free) later found fragrance-free green cleaners significantly lower in total VOC concentration and VOC count than conventional ones, while green-with-fragrance cleaners were not significantly different, which supports the advice for cleaners but not yet for baby products. Hamann 2015 shows a different but relevant caution: even 'fragrance-free' US pediatric products commonly contain non-fragrance contact allergens (80.8% of 52 had >=1 NACDG-tray allergen, mostly preservatives), so 'fragrance-free' is more reliable specifically against added-scent VOCs, not against contact allergens generally.
Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact
What you can do / Measured in people or real products
Taking the air freshener out of the car removes its main added chemical: without one, in-car limonene was about 5-6 ug/m3.
Moderate evidence: Small pilot; limonene only.
What you can do / Measured in people or real products
When 100 teenage girls swapped their usual personal care products for ones labeled free of phthalates, parabens, triclosan, and oxybenzone for just 3 days, levels of these chemicals in their urine fell by 27-45%.
Moderate evidence: No control arm, 100 Latina girls in one town, 3 days, summer.
Source: Harley 2016, Environmental Health Perspectives Link to this fact
What you can do / Self-reported survey
A fragrance-free sign is not enough on its own: Canadians with chemical sensitivities described workplaces and hospitals with 'scent-free' policies where staff still wore scents and scented cleaners stayed in use.
Moderate evidence: Qualitative focus groups, n=60 self-selected MCS/IAQ-affected Canadians; advocacy-funded.
Source: Roy 2026 Link to this fact
What you can do / Review of other studies
Smell scientists reviewing the evidence found that scenting workplaces to boost mood or productivity is not well supported, and noted that a chemically intolerant employee can react to a fragranced workplace.
Moderate evidence: Short narrative review; the positive-scent literature it weighs is small; no primary data.
Source: Dalton & Jaén 2010, Current Opinion in Allergy and Clinical Immunology Industry-funded Link to this fact
What you can do / Review of other studies
If you are allergic to fragrance, dermatologists advise avoiding all fragrance rather than only the chemicals you tested positive to, and choosing products from a checked database such as the ACDS CAMP list or SkinSAFE instead of trusting 'fragrance-free' claims.
Moderate evidence.
Caveats
Expert advice, untested against label reading; COI: authors built/lead CAMP. Noiesen 2007 (382 patch-test-confirmed allergic patients) now quantifies why the review distrusts label reading: 46% of allergic patients found reading ingredient labels difficult or extremely difficult, education-graded, still 38% among fragrance-only patients. This corroborates the rationale for recommending a database over labels but does not test whether database-guided avoidance actually outperforms label reading on outcomes, so the grade stays moderate.
What you can do / Animal study
Treat essential oils as perishable: keep bottles closed and don't keep old, long-opened oils for skin use, because their scent chemicals oxidize into skin allergens in air.
Moderate evidence: Mechanism shown in lab (open flasks); real-bottle oxidation rates and the benefit of these habits not tested.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
What you can do / Measured in people or real products
How often someone used body lotion and perfume was directly linked to how much of the synthetic musks galaxolide and tonalide were in their blood, giving direct human evidence that switching to musk-free lotions and perfumes could lower blood levels of these fragrance chemicals.
Moderate evidence: Cross-sectional frequency-of-use questionnaire, not an intervention; the link was not shown for musk ketone or musk xylene, only for the polycyclic musks.
Source: Hutter 2009, Science of the Total Environment Link to this fact
What you can do / Measured in people or real products
In a study of 25 UK homes, easy-to-check building factors (home age, size, number of occupants, single- vs double-glazing) showed no measurable relationship to indoor scent-chemical levels; the homes with the highest levels were those whose occupants reported heavy cleaning/fragrance-product use.
Moderate evidence.
Caveats
Glazing comparison used t-tests on 19 homes with no ventilation-rate data; product-use link is a qualitative activity-log correlation, not a controlled experiment A larger same-lab study (Heeley-Hill 2021, 60 UK homes, daily diaries; Givaudan-funded fieldwork) found cumulative product-use frequency had almost no predictive power for measured VOC levels (R²<0.001), so treat the product-use link as suggestive.
Source: Wang 2017, Environmental Science: Processes & Impacts Link to this fact
What you can do / Measured in people or real products
Because galaxolide (HHCB) levels in milk tracked perfume use and tonalide (AHTN) levels tracked scented-laundry-detergent use specifically, choosing fragrance-free perfume and fragrance-free laundry detergent during pregnancy and breastfeeding are each independently plausible ways to lower the corresponding musk chemical passed to a nursing infant.
Moderate evidence.
Caveats
Correlational and cross-sectional, no before/after intervention trial; musk xylene (a nitro musk) showed no association with any product category tested, so this action would not address that compound.
Source: Lignell 2008, Environmental Science & Technology Link to this fact
What you can do / Measured in people or real products
A direct chemical test of real fragrance products found no build-up of the allergenic breakdown product (linalool hydroperoxide) even after 9 months of worst-case accelerated aging, so for fine fragrances and antiperspirants specifically, letting a bottle sit open for months to years did not measurably increase this particular hazard.
Moderate evidence.
Caveats
Covers only fine fragrance and antiperspirant formulations tested by one industry lab; does not cover creams, lotions, or other product categories, and does not test whether the general advice to discard old products reduces dermatitis.
Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact
What you can do / Self-reported survey
If you are allergic to a fragrance or preservative chemical, reading cosmetic ingredient labels is genuinely difficult, not just for you: in one clinical survey, 46% of patch-test-confirmed allergic patients found it difficult or extremely difficult, and this was significantly worse for people with less education.
Moderate evidence: Single-country (Danish), 3-clinic, self-rated VAS survey of 382 patients; not replicated elsewhere, so per our grading rule it stays below strong.
What you can do / Self-reported survey
People allergic to formaldehyde or methyldibromo glutaronitrile (MDBGN) have an especially hard time reading ingredient labels, likely due to long chemical names and formaldehyde's many synonyms and releasers; ask a dermatologist to write down or print the specific names and synonyms to watch for.
Moderate evidence: Single Danish survey; the mechanism (long/unfamiliar names) is the authors' plausible explanation, not directly tested.
What you can do / Measured in people or real products
A fading chemical smell is not a sign that exposure or irritation has stopped: PGME-exposed subjects lost the ability to smell the compound after about 3 hours at 250 ppm, while eye and nose irritation continued or worsened in those who stayed in the chamber.
Moderate evidence: Demonstrated only for PGME vapor at occupational-accident-level concentrations (hundreds of ppm), not for consumer-level scented product exposure.
Source: Stewart 1970 (Arch Environ Health), Archives of Environmental Health: An International Journal Industry-funded Link to this fact
What you can do / Measured in people or real products
Switching from a fragranced to a fragrance-free laundry detergent cut the fragrance chemical D-limonene coming out of the dryer vent by up to 99.7% (mean 79.1%) within one month, in real households, with no extra cost or apparent inconvenience.
Moderate evidence.
Caveats
4 households switched, D-limonene only; one household's no-product baseline (machine run with no detergent) actually rose 70.3% after the switch, which the paper attributes to residual fragrance chemicals left in the machine or clothing; no statistical testing.
Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact
What you can do / Self-reported survey
Reducing overall frequent use of chemical household products (disinfectants, bleach, aerosols, air fresheners, and similar) during pregnancy, rather than switching to any one particular product believed to be safer, is the action this study's findings point to.
Moderate evidence.
Caveats
This is an inference from the dose-response composite-score finding and the null single-product-removal analysis, not a tested intervention; the study did not test whether reducing product use lowers a child's wheeze risk.
What you can do / Self-reported survey
Only 5% of nurses in this study reported using a face mask or respirator when handling disinfectants, and use was more common among nurses with worse asthma control (likely because symptomatic nurses sought protection, not because protection failed); the authors explicitly recommend prioritizing elimination or substitution (e.g., non-chemical disinfection methods such as steam or UV light) over personal protective equipment as the more effective prevention strategy.
Moderate evidence.
Caveats
Because so few nurses used respiratory protection, the study was underpowered to test whether it actually modified the disinfectant-asthma-control association (P-interaction >=0.40, not significant either way).
Source: Dumas 2017, European Respiratory Journal Link to this fact
What you can do / Other evidence
Placing a reed diffuser closer to where you sleep (a bedside cupboard) rather than farther away (a dresser) raised the modeled chemical level in the breathing zone by about 38% after a week.
Moderate evidence: Modeled, not directly measured in an occupied room; specific to this product's emission rate and this bedroom geometry.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Other evidence
Doubling a room's air exchange rate (more ventilation) cut the modeled breathing-zone reed-diffuser chemical concentration to about 60% of the low-ventilation level.
Moderate evidence: Modeled, not directly measured; China-specific ventilation-rate assumptions.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Test-chamber measurement
More fiber sticks in a reed diffuser sharply raise the chemicals it releases: modeling showed one stick could raise the indoor chemical level roughly 9- to 11-fold, and two sticks roughly 19- to 24-fold, compared to the bottle alone.
Moderate evidence: Modeled from one product's fitted transport parameters; relative multiplier, not an absolute health-relevant dose.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Measured in people or real products
In this 1996 sample, 3 of 73 deodorants labeled "not perfumed" genuinely contained none of the 21 fragrance substances tested, on chemical analysis.
Moderate evidence: Very small sample (n=3) from one country/year snapshot; does not establish that "not perfumed"/"fragrance-free" labels are reliable in general or in other markets/years.
Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
Because hormone-disrupting chemicals cluster by product type, cleaners, synthetic detergents, fabric softeners, air fresheners, and deodorants are the household product categories where checking for isothiazolinone preservatives (such as benzisothiazolinone) and fragrance chemicals (such as hexyl cinnamaldehyde, geraniol, and citronellol) is likely to be most worthwhile.
Moderate evidence: Reflects which chemicals are most often listed in this product database, not which products emit the most or pose the greatest measured exposure.
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
What you can do / Government agency
HUD's own 1991-92 guidance gives two concrete examples of reasonable accommodation for chemically sensitive tenants: (1) a tenant sensitive to pesticides can ask for advance notice before the building is fumigated and for boric acid to be substituted for the chemicals normally used; (2) an applicant sensitive to carpet chemicals can ask the housing provider what type of carpeting is used throughout the building before deciding whether to rent.
Moderate evidence.
Caveats
These are HUD's own worked examples from internal guidance, not a binding regulation with a fixed list of required accommodations; HUD explicitly says reasonableness depends on the individual's circumstances and is bounded by undue financial/administrative burden.
Source: HUD guidance (1991) Link to this fact
What you can do / Government agency
After a 1993 ADA complaint over municipal-employee perfume use, San Francisco voluntarily adopted a policy requiring public meeting notices to ask attendees to refrain from wearing perfume or other scented products, to let people with environmental illness or multiple chemical sensitivity attend.
Moderate evidence: One city's voluntary accommodation, reported secondhand in DOJ's own letter; not evidence the policy was enforced or effective, and not a legal requirement.
Source: DOJ Civil Rights Division 1993 (TAL 383) Link to this fact
What you can do / Government agency
A resident of HUD-assisted housing with a documented chemical sensitivity can cite this HUD exhibit directly when requesting advance notice before common-area cleaning and nonchemical cleaning products where practical, since HUD's own guidance names these as accommodations that are not an undue burden.
Moderate evidence.
Caveats
Applies specifically to HUD-assisted (Section 504-covered) multifamily housing; the same specific accommodations are not guaranteed at privately owned housing covered only by the Fair Housing Act, where the undue-burden analysis is done case by case.
Source: HUD Occupancy Handbook 4350.3 REV-1, Exhibit 2-6 (2007) Link to this fact
What you can do / Government agency
People who want to minimize systemic absorption of chemical UV filters while the additional toxicology studies FDA has requested remain outstanding can choose mineral-only sunscreens with zinc oxide or titanium dioxide as the active ingredient, the two filters FDA's own review has found 'generally recognized as safe and effective,' or rely on protective clothing and shade alongside sunscreen.
Moderate evidence.
Caveats
This is not a claim that chemical-filter sunscreens are unsafe, and it is not advice to avoid sun protection; the paper explicitly says its results do not indicate people should refrain from sunscreen use.
Source: Matta 2019, JAMA Link to this fact
What you can do / Other evidence
Hairdressers, salon workers, and professional or domestic cleaners can reduce workplace asthma risk with ventilation, gloves, and lower-irritancy products or application methods where available, since this population-based cohort found both hairdressing and cleaning occupations, and reactive cleaning/disinfecting chemical exposure specifically, associated with higher adult-asthma risk.
Moderate evidence.
Caveats
The study cannot identify which specific chemicals within 'hairdressing' or 'cleaning/disinfecting' exposure are responsible, so this is general occupational-hygiene advice, not a product-specific recommendation.
What you can do / Review of other studies
Whether an odor affects mood or physiology depends more on how pleasant a person finds it and what they expect it to do than on which specific plant or chemical produced it; hedonic (liking) ratings predicted physiological and psychological outcomes across most of the 18 studies reviewed.
Moderate evidence: Narrative synthesis across 18 heterogeneous studies using different odors, doses and measures; not a meta-analysis.
Source: Herz 2009, International Journal of Neuroscience Industry-funded Link to this fact
What you can do / Other evidence
Ozone-generating 'air purifiers' can turn the scent chemicals in air fresheners and cleaners into fine particles; the authors advise avoiding indoor ozone sources and cutting back on terpene-heavy scented products, especially on high-ozone summer days.
Moderate evidence: The advice is the authors' inference from chamber results; no health outcome was measured and ozone levels were set by a generator, above typical outdoor-to-indoor ozone.
Source: Sarwar 2004, Journal of the Air & Waste Management Association Link to this fact
What you can do / Other evidence
Obstetric and gynecologic bodies (FIGO 2015, RCOG 2013) advise that pregnant women be told the sources of chemical exposure and how to reduce them, as a precaution despite uncertain evidence; in a French survey, 54.3% of 300 women had never heard of endocrine disruptors.
Moderate evidence: Advice is precautionary and says causal evidence is lacking; the review does not test whether avoidance improves birth outcomes.
Source: Street 2020, International Journal of Molecular Sciences Link to this fact
What you can do / Other evidence
The industry panel warned that cetrimonium bromide and palmitoyl carnitine can enhance skin penetration of other chemicals (phenylazoaniline, benzocaine, benzoic acid), so products combining them with ingredients whose safety depends on low absorption need careful formulation.
Moderate evidence.
Caveats
Penetration enhancement shown in artificial membranes (enhanced below 0.5%, inhibited above 1.0%); no human product data. CIR is financed by the Personal Care Products Council, the cosmetics industry trade association.
Source: Becker et al. 2012 (CIR), Int J Toxicol, International Journal of Toxicology Industry-funded Link to this fact
What you can do / Other evidence
CTV reported that the Environmental Health Association of Québec (ASEQ-EHAQ), after the woman's death, launched a national campaign and fundraiser to get housing for people with MCS across Canada, and its president advocates a national program to build chemical-free homes.
Moderate evidence: Advocacy group's own account as relayed by CTV; the group is not independent of the cause. Article subject is a death by MAiD; add 988 line in published use.
Source: CTV News, April 2022 (via Smoke-Free Housing BC; redacted copy), CTV News (news article) Link to this fact
What you can do / Other evidence
OSHA recommends scheduling cleaning or maintenance work when other occupants are absent and limiting the amount and location of chemicals used near workers.
Moderate evidence: Advisory administrative controls; no evidence of effectiveness given.
Source: OSHA 3430-04, 2011 Link to this fact
Information, not medical advice. See also: myths we won’t tell you.