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.
Skin allergy / Other evidence
The rash from acetophenone azine usually starts on the lower leg where the shin guard sits, can spread to a whole-body rash, and may later appear on the soles from insoles or flip-flops.
Weak evidence: Based on case reports; a pattern in a handful of patients, not an estimated frequency.
Skin allergy / Other evidence
Hair-straightening ('Brazilian keratin') products containing formaldehyde have caused airborne facial dermatitis with severe edema, and breathing symptoms in clients and hairdressers.
Weak evidence: Case reports and clinical observations summarized in a review; no exposure measurements in this paper.
Skin allergy / Other evidence
Dermatologists disagree on the best patch-test material for lanolin: one study found Amerchol L101 caught 3.9% of patients versus 1.1% for wool alcohol, while another found it no better, so more than one preparation may be needed.
Weak evidence: Narrative review of small studies; no consensus, and Amerchol L101 contains mineral oil that can cause irritant reactions.
Source: Johnson 2023, Cutis Link to this fact
Skin allergy / Other evidence
Disinfectant-degreasers rich in cationic surfactants can cause a red, burn-like rash on the hands, often 1 to 4 weeks after starting, that clears 15 to 30 days after stopping; the review illustrates it with one atopic kitchen intern.
Weak evidence: One authors' case, diagnosed by timing without patch tests; time course is relayed from a 1995 cetrimide report.
Source: Lauriola 2025, Italian Journal of Dermatology and Venereology Link to this fact
Skin allergy / Other evidence
Benzalkonium chloride (BAK), a preservative in many eye drops, can cause an allergic rash on the eyelids and around the eyes; in three Australian women a positive patch test to BAK matched months of using BAK-preserved drops, and the rash improved after they switched to preservative-free drops.
Weak evidence: Three cases, no controls, one region; irritant versus allergic reaction was judged clinically. It shows the problem happens, not how often.
Source: Kannen 2026, Australasian Journal of Dermatology Link to this fact
Skin allergy / Other evidence
Danish allergy centers reported textile-dye allergy as rare: 2 of 1,000 Danish skin-ward patients tested in six months had dye-caused allergic eczema, against 'not unusual' 50 of 1,000 in Italy, and cases were mostly with new, unwashed clothes.
Weak evidence: Centers' own account relayed by the report; no data table, definition of case or testing method given; Italian comparison is a verbal statement.
Source: Danish EPA 2014, Survey of Chemical Substances in Consumer Products No. 129 Link to this fact
Skin allergy / Review of other studies
Shorter-chain ceramides make the skin's fat layers pack more loosely and leak more: in lab membranes, swapping a 24-carbon fatty acid for a 16-carbon one raised permeability.
Weak evidence: Artificial membranes and porcine skin, not human skin in use; chemical-specific penetration was not tested.
Source: Berdyshev 2024, Allergy, Asthma & Immunology Research Link to this fact
Skin allergy / Review of other studies
Anti-IL-4 receptor treatment (dupilumab) brings ceramide chain length, the key acylceramide CER[EOS] and water loss through skin back toward normal in people with eczema, but a second signal, TSLP, can still hold down the protein-bound ceramides.
Weak evidence: Single lipidomic study behind the normalization claim; the TSLP point is inferred from cell work and an unreplicated cohort.
Source: Berdyshev 2024, Allergy, Asthma & Immunology Research Link to this fact
Skin allergy / Review of other studies
Psoriasis skin shows fewer ultra-long-chain ceramides, free fatty acids and phytoceramide, which lowers the lipid layers' structural transition temperature.
Weak evidence: Brief mention, two cited studies; the IL-17 mechanism is not worked out.
Source: Berdyshev 2024, Allergy, Asthma & Immunology Research Link to this fact
Skin allergy / Other evidence
EPA's 2006 ADBAC review recorded 'not a dermal sensitizer' from a guinea pig study, while its own incident section lists hives and allergic contact dermatitis among human reports for quat products.
Weak evidence: Incident reports are voluntary and pooled across all quats without confirmation; one animal test does not settle human allergy.
Source: EPA RED 2006 Link to this fact
Skin allergy / Other evidence
The EU committee called behentrimonium chloride 'a skin sensitizer' because 26% of guinea pigs reacted in one Buehler test, but a second Buehler test on the same substance and a 104-person human repeat-insult test at 3.4% were negative.
Weak evidence.
Caveats
Animal tests with equivocal reactions and challenge concentrations below the requested use level; the committee itself judged the human repeat-insult test unethical; conflicting results.
Source: SCCP 2006 Industry-funded Link to this fact
Skin allergy / Government agency
Alpha-isomethyl ionone ranks as an established human contact allergen in the EU opinion (category ++, 11-100 reported cases), but individual patch-test studies found positive rates of 0% to 2.1%, and the industry's own review lists four negative human induction tests.
Weak evidence: Low case counts and low prevalence; the industry review is the industry's position; the ++ rating partly reflects how often it has been tested.
Skin allergy / Other evidence
The CIR draft records that polysorbate 60 and a polysorbate 60-based cream caused hives (urticaria) within 20 minutes on the forehead of test subjects, but its Summary and Discussion say polysorbate 60 at 100% was 'not dermally irritating'.
Weak evidence: The urticaria entry is a one-line summary of an old study with no n or amount; the conflict is within the draft's own text.
Source: CIR 2015 draft Industry-funded Link to this fact
Skin allergy / Other evidence
Tooth-whitening strips with 6% hydrogen peroxide caused oral irritation in about 22% of subjects on average in the retrospective data cited by the CIR draft, and 25.0% in a trial of 9 mg strips; adverse events were described as transient.
Weak evidence: Secondary citation, product-specific and not about everyday personal care; industry-funded panel; EU limits consumer oral products to 0.1%.
Source: CIR 2018 draft (Do Not Cite or Quote; PCPC-funded CIR) Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Reading a patch test a second time on day 7 revealed extra hydroperoxide allergies: 8% of limonene-hydroperoxide and 4% of linalool-hydroperoxide positives were negative or doubtful on day 3.
Weak evidence: One-clinic count (6 of 77 and 4 of 96); a day-7 reading is a clinic practice, not something consumers control.
Source: Dittmar & Schuttelaar 2019, Contact Dermatitis Link to this fact
Skin allergy / Government agency
In the NARC-commissioned model, the sick-day inputs assume people with a fragrance allergy diagnosis are off work 5.6 days a year and people without one 2.1 days.
Weak evidence.
Caveats
Both numbers come from a Danish eczema cohort (Saetterstrom 2014). The report measured no sick leave in fragrance allergy, and the cost model is sensitive to them (one day more or less changes one case's cost by about 5%).
Source: COWI 2019 Link to this fact
Skin allergy / Other evidence
In Denmark, about 70% of recognized occupational contact dermatitis cases are attributed to irritant exposures and 30% to allergy; other occupational series cited in the review give 75% (Saarland notifications) and 57% (Northern Bavaria, plus 15% combined).
Weak evidence.
Caveats
Shares for compensated or notified cases in two countries, not a general rate; ICD is an exclusion diagnosis whose criteria include irritant exposure, which may inflate the irritant share in high-exposure jobs; cited by the review, not measured by it.
Source: Jacobsen 2022 Link to this fact
Skin allergy / Self-reported survey
A previous rash from perfumed cosmetics was significantly associated with a positive patch test to the product perfumes (p = 0.001), suggesting the reactions were clinically relevant.
Weak evidence: Self-reported rash history; association test only, clinic patients.
Source: Johansen 1997, Contact Dermatitis Link to this fact
Skin allergy / Other evidence
Rosacea patients' own cosmetics and medicines almost never caused allergic reactions: 133 patch tests of patients' own products (21 patients) gave no positive reactions, only a few irritant or doubtful ones.
Weak evidence: Only 21 patients; product categories mostly 1-6 tests each; low power to detect rare allergy.
Skin allergy / Other evidence
If a skin-care product or topical treatment seems to make rosacea worse, ask a dermatologist for patch testing that includes your own products and any eye drops or medicines you use.
Weak evidence: Recommendation from a small study; no rosacea flare occurred in any patch-test-positive patient.
Skin allergy / Other evidence
In the manufacturer's own pooled patch tests, the rate of skin reactions to sunscreens with 1-6% oxybenzone did not rise with the oxybenzone concentration, and photoallergy tests and standard repeat patch tests gave the same low rate (about 0.27% vs 0.26%).
Weak evidence: Sponsor-held data from healthy adults; per-formula averages, not pooled individual data; the null concentration trend spans only 1-6% with most formulas at 6%.
Source: Agin 2008 (oxybenzone HRIPT), Photodermatology, Photoimmunology & Photomedicine Industry-funded Link to this fact
Skin allergy / Other evidence
Allergic hand eczema had the poorest outcome of the types studied (mean sick leave 28.6 weeks vs 13.0 for irritant and 11.8 for atopic), which the authors cite as support for rules that cut allergen exposure.
Weak evidence: One survey with self-reported subtype and sick leave; the policy conclusion is the authors' interpretation.
Skin allergy / Other evidence
After Denmark's nickel regulation, the link between nickel allergy and hand eczema in young women disappeared (OR 3.63 in 1990 to 0.65 in 2006 for women aged 18-35).
Weak evidence: Two cross-sectional surveys by the review's own authors, with wide confidence intervals (1.33-9.96 and 0.29-1.46); cause and effect not established.
Skin allergy / Other evidence
If you have recurring hand rashes, see a dermatologist and ask about patch testing, because in a 15-year Swedish follow-up cited by the review, contact allergy (including nickel allergy) was linked to hand eczema that persisted.
Weak evidence: Weak, single-survey evidence; patch testing advice is general good practice rather than a finding of this review.
Skin allergy / Measured in people or real products
Of patients allergic to oakmoss (Evernia prunastri), 96% reacted to fragrance mix I, but only about half of those allergic to tree moss (Evernia furfuracea) reacted to either standard mix.
Weak evidence: Single clinic; tree-moss reactions are heterogeneous (some are resin-acid reactions) and colophonium was not analyzed.
Skin allergy / Measured in people or real products
The allergy rate to HICC (a synthetic lily-of-the-valley scent) was 2.1% overall and fell from 2.8% in 2011 to 1.4% in 2014 before rising to 1.8% in 2015; the authors could not say whether exposure changed.
Weak evidence: Single clinic, age and sex standardized, yearly samples of about 950 patients; no exposure data.
Skin allergy / Other evidence
In one multicenter study, patients allergic to oxidized linalool scored worse on a fragrance quality-of-life questionnaire (69 vs 58 out of 130) than other fragrance-allergic patients.
Weak evidence: One of ten allergen comparisons, no multiple-testing correction, cross-sectional; the authors' explanation (frequent exposure to the most-labeled fragrance allergen) is untested.
Source: Bennike et al. 2019, Contact Dermatitis Link to this fact
Skin allergy / Other evidence
US dermatologists added jasmine and peppermint to the extended allergy panel even though reactions are less common than to other fragrances, because both are also used as flavorings (e.g., peppermint in toothpaste causing lip inflammation).
Weak evidence: Rationale rests on case reports and cited reviews; the paper gives no prevalence numbers for either.
Skin allergy / Review of other studies
A clinical review describes quaternary ammonium disinfectants as possibly causing asthma 'through a presumably sensitizing mechanism', in contrast to the irritant mechanism of chlorine, ammonia and acids.
Weak evidence: The mechanism is described as presumed; an industry-funded methodological review disputes the human evidence.
Source: Lemiere 2022, The Journal of Allergy and Clinical Immunology: In Practice Link to this fact
Skin allergy / Other evidence
Benzyl alcohol, a preservative that also counts as a fragrance allergen, caused a positive patch test in 0.5% (15 of 3,050) of North American patients, with the highest current-relevance rate of any allergen (93.3%).
Weak evidence: Only 15 reactions; 8 of 14 relevant ones were 'possible' (contact judged likely) rather than verified; referral population.
Skin allergy / Measured in people or real products
The authors warned that most cosmetic reactions never reach a dermatologist and that true incidence 'may be appreciably higher', after first reasoning that unseen reactions are equally few.
Weak evidence: Internally inconsistent reasoning in the paper; no data on unseen cases.
Source: Eiermann 1982, Journal of the American Academy of Dermatology Link to this fact
Skin allergy / Review of other studies
A 2004 review by Unilever and London clinic authors concluded benzalkonium chloride (a common preservative and disinfectant) is a clear skin irritant and that many reports of allergy to it are probably irritant patch-test reactions misread as allergy.
Weak evidence.
Caveats
Opinion-based review with no search method; two of four authors worked at Unilever, which sells surfactant-containing products, and no funding statement is printed. Later clinic series (Mayo, Boston, Melbourne) disagree on how much is true allergy.
Source: Basketter et al. 2004, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
When 1,775 patients were patch tested with 0.1% benzalkonium chloride (the routine concentration), the cited German study found more irritant than allergic reactions, and the review's authors suggest true allergy may show only at 0.01%.
Weak evidence.
Caveats
Secondhand relay of an older German-language series; the review gives no counts of irritant versus allergic reactions. A later study cited elsewhere in our evidence base found 0.1% may miss real allergy, so the best concentration is unsettled.
Source: Basketter et al. 2004, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
Animal tests of benzalkonium chloride as a skin sensitizer are mixed: a guinea pig test found 4 of 19 animals positive on skin challenge at 10%, and a modified Buehler test found 20% responding, while the standard mouse lymph node assay was negative.
Weak evidence: All relayed; the authors treat the positives as likely false positives from irritation, which is their interpretation, not a tested finding.
Source: Basketter et al. 2004, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
If a patch test says you are allergic to benzalkonium chloride, ask for a repeat test or a use test of the actual product before concluding it is an allergy, since irritation can look the same.
Weak evidence: Clinical advice from an industry-affiliated review; not a test of outcomes.
Source: Basketter et al. 2004, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
Few sunscreen shoppers raised ingredient worries: among 325 top-voted reviews, nanoparticles were named in 7 comments (2%) and oxybenzone, avobenzone, parabens, homosalate and retinyl palmitate in about 3 each (1%).
Weak evidence: Top-voted comments only; absence of mention is not absence of concern, and many shoppers may not know which filters are in the product.
Skin allergy / Other evidence
A dermatologist-reported case: a 30-year-old woman got a rectangular itchy rash on her shin in the shape of an antibacterial bandage pad and had strong patch-test reactions to benzalkonium chloride, the pad's only antibacterial ingredient.
Weak evidence: Single case; no irritant controls or repeat testing, so allergy is not separated from irritation.
Skin allergy / Other evidence
The same patient also reacted strongly (++) to cetrimonium chloride, a related quaternary ammonium ingredient that the authors say may cross-react with benzalkonium chloride.
Weak evidence: One patient; co-reaction is not proof of cross-reactivity.
Skin allergy / Government agency
The EPA work plan lists ADBAC as a corrosive dermal irritant (category I) and 'not a dermal sensitizer' or photosensitizer, based on registrant guinea pig studies, while also summarizing case reports of work-related asthma and quat-related incidents.
Weak evidence: Registrant-submitted unpublished studies summarized by EPA; a negative guinea pig test does not rule out human allergy (see our benzalkonium patch-test material).
Source: US EPA 2017 Link to this fact
Skin allergy / Other evidence
Of NACDG 2021-2022 patients who reacted to benzyl alcohol, 93.3% had a currently relevant reaction, the highest of any tested allergen, but this is 14 of 15 patients and in the primary 8 of the 14 were only 'possible' relevance.
Weak evidence: Tiny denominator; relevance is clinician-judged; the review does not report the 'possible' split. Cutis authors read it as strong evidence the positives are reliable.
Source: Zheng et al. 2026, ACDS Allergen of the Year (Cutis), Cutis Link to this fact
Skin allergy / Other evidence
Case reports describe a person whose hand eczema got worse on a corticosteroid cream containing benzyl alcohol and also on moist toilet paper preserved with it; stopping both gave complete remission.
Weak evidence: Single case report; no rate. Shows a mechanism, not frequency.
Source: Zheng et al. 2026, ACDS Allergen of the Year (Cutis), Cutis Link to this fact
Skin allergy / Other evidence
Benzyl alcohol usually causes delayed (type IV) contact allergy, with eczema, papules or vesicles, but less often it can cause immediate reactions (hives, angioedema) after exposure.
Weak evidence: Immediate reactions rest on a few case reports; the review does not separate allergic from nonimmunologic urticaria.
Source: Zheng et al. 2026, ACDS Allergen of the Year (Cutis), Cutis Link to this fact
Skin allergy / Other evidence
In one published case, an 81-year-old woman developed large hemorrhagic blisters and eczema exactly where a plaster of Paris splint touched her skin; patch tests were positive (1+) to the same brand of plaster and to benzalkonium chloride 0.1% in petrolatum.
Weak evidence: Single patient, no irritant controls, only 1+ reactions; benzalkonium chloride is also a recognized irritant, and other hospital exposures were not excluded.
Source: Wong and Watson 2001, Australasian Journal of Dermatology Link to this fact
Skin allergy / Other evidence
The same plaster that caused a severe reaction on the arm gave a positive patch test only when applied wet, not dry, so the authors suggest water may be needed to release the allergen or help it enter the skin.
Weak evidence: Authors' hypothesis from one patient; untested.
Source: Wong and Watson 2001, Australasian Journal of Dermatology Link to this fact
Skin allergy / Other evidence
Plaster of Paris allergy is very rare: the authors found only seven earlier English-language reports, mostly with Gypsona and positive tests to benzalkonium chloride 0.1%.
Weak evidence: Rarity of reports is not rarity of reactions; the search is not systematic and is from 2000.
Source: Wong and Watson 2001, Australasian Journal of Dermatology Link to this fact
Skin allergy / Measured in people or real products
Wet work of 2 hours or more a day (occupational plus domestic) was not significantly associated with hand eczema after adjustment in a car-industry case-control study (irritant hand eczema OR 1.62, 95% CI 0.78-3.37), although it was more common in irritant cases univariately (49.1% vs 31.7%).
Weak evidence: Underpowered for exposure effects by the authors' own account; workplace had strong skin-protection policy; a null here is not evidence wet work is harmless.
Source: Apfelbacher et al. 2010, Contact Dermatitis, Contact Dermatitis Link to this fact
Skin allergy / Self-reported survey
Apprentice nurses who washed their hands 8 or more times per shift had about 1.5 times the odds of hand eczema (OR 1.5, 90% CI 1.02-2.25) in a multivariate model.
Weak evidence.
Caveats
Lower CI bound barely above 1 and given at 90% (one-sided testing), not 95%; observational; self-recorded exposure and symptoms; 20 participants may have had HE before training; same cohort as Part II, not independent replication.
Source: Visser et al. 2014 (Part I), Contact Dermatitis, Contact Dermatitis Link to this fact
Skin allergy / Self-reported survey
In the same nurse cohort, alcohol-based hand rubs and non-gel disinfectants showed no association with hand eczema (disinfectants OR 1.1, 90% CI 0.69-1.79), while soap and detergent contact showed only a non-significant tendency (OR 1.5, 0.97-2.30).
Weak evidence.
Caveats
Absence of significance in a modest cohort with wide intervals is not evidence of safety; exposure counted per shift, not by product ingredient; some apprentices with damaged skin stopped using gels because they stung.
Source: Visser et al. 2014 (Part I), Contact Dermatitis, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
Of 52 symptomatic apprentice nurses examined by an occupational physician, 90% were diagnosed with contact dermatitis, most commonly irritant contact dermatitis (40% without atopy, 27% with atopic dermatitis).
Weak evidence: Fewer than a third of those invited attended, so the 52 are a self-selected subset; no patch testing, so irritant versus allergic cannot be separated.
Source: Visser et al. 2014 (Part I), Contact Dermatitis, Contact Dermatitis Link to this fact
Skin allergy / Other evidence
The authors caution against telling people with atopic dermatitis to avoid one class of preservatives, because swapping one preservative for another may move sensitization to a less common weak allergen.
Weak evidence: Argument from association data; no substitution or product-use data in the study.
Source: Kohli & Nedorost 2016, Journal of the American Academy of Dermatology Link to this fact
Skin allergy / Other evidence
In a U.S. consortium of 1,466 mother-child pairs, higher paraben levels in a pregnancy urine sample went with modestly higher odds that the child was diagnosed with eczema by age 3 (OR 1.13, 95% CI 1.02-1.26 per standard-deviation increase in the molar sum of methyl, ethyl and propyl paraben).
Weak evidence.
Caveats
Single spot urine, parent-reported diagnosis, no multiple-comparison correction across 15 phenols x 3 outcomes x sex strata, lower CI bound 1.02; association not causation; one consortium.
Source: Miller 2025 (ECHO), Environment International Link to this fact
Skin allergy / Other evidence
Scented laundry and cleaning products (hair-styling products, laundry detergent, fabric softener, usually floral-scented) formed one group of odors migraine patients named, and chronic migraine patients named this group more often than episodic patients (P = 0.037).
Weak evidence.
Caveats
Only 16 chronic patients, no correction for multiple tests, and the paper's own percentages do not reconcile; cross-sectional, so it cannot show that chronic migraine increases sensitivity.
Skin allergy / Other evidence
36.4% of surveyed UAE women reported an adverse reaction to cosmetics in the past 2 years, mainly skin redness (20.6%), pimples (18.4%) and itching (16.9%); skincare (21.7%) and makeup (14.1%) were blamed far more often than perfume (5.2%).
Weak evidence.
Caveats
Open-link snowball sample of 461 women, mostly young and university-educated; self-report, no exposure measurement; not weighted, so not a UAE prevalence. Mixes fragrance-related and non-fragrance reactions (pimples, hair loss, pigmentation); attribution is the respondent's own.
Source: AlBlooshi 2026, Frontiers in Toxicology Link to this fact
What you can do / Measured in people or real products
Childcare rooms with more fresh-air exchange had lower levels of several of the chemicals measured.
Weak evidence: Bivariate correlations, 34 rooms.
What you can do / Measured in people or real products
Keep scented products closed and avoid old, long-opened ones: limonene and linalool became skin irritants after weeks of air exposure.
Weak evidence.
Caveats
Extrapolated from lab-oxidized neat material (10-20 weeks air exposure); product storage not tested by this paper. Two independent industry market surveys have now directly tested the specific mechanism this advice assumes (in-bottle oxidation with age) and both found it absent: Kern 2014 (39 aged fine fragrances + 29 antiperspirants, 9 months accelerated storage) and Natsch 2019 (104 products spanning fine fragrances, antiperspirants, creams, and lotions, including two fine fragrances tracked 3-6 years at room temperature) both found no progressive hydroperoxide accumulation with age, and consumer-product doses 2-4 orders of magnitude below elicitation/sensitization thresholds. Both studies are industry-funded (IDEA consortium: Givaudan, Firmenich, IFF, IFRA) and not independently replicated by a non-industry group, and neither tests essential oils or raw materials (separately known to accumulate hydroperoxide) or every product category. Moved to claims-to-avoid because the specific mechanistic basis for this advice (in-container autoxidation) is now negative in the only two real-product tests that exist, even though the underlying autoxidation chemistry itself, in neat/essential oils, is not disputed. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Bråred Christensson 2009, Contact Dermatitis Industry-funded Link to this fact
What you can do / Review of other studies
Old, long-opened scented products are more allergenic than fresh ones, because the scent chemicals oxidize on contact with air.
Weak evidence.
Caveats
Time course is primary for lavender oil (Hagvall 2008: LLNA EC3 36% fresh -> 23% at 10 weeks -> 4.4% at 45 weeks in the same batch), but in neat oil in open lab flasks, not formulated products as stored. Kern 2014 first closed part of this gap (39 fine fragrances + 29 antiperspirants, no accumulation over 9 months accelerated storage); Natsch 2019 extends this to 104 products across more categories (adding limonene, creams, lotions) and to multi-year real-time storage (two fine fragrances tracked 3-6 years at room temperature, no accumulation), plus tests products donated by allergic patients themselves (also negative for hydroperoxide). Downgraded to avoid because the specific claim — that aging/opening itself makes a product more allergenic via in-container oxidation — has now failed two independent, broader industry market surveys with no non-industry evidence on the other side; creams, lotions, and fine fragrances/antiperspirants are covered, though essential oils, raw materials, and other categories remain untested and are not covered by this downgrade. Kern 2014 and Natsch 2019 are both industry studies (Givaudan / IDEA consortium) with Natsch as a co-author on both, so they are not independent replications of each other.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
What you can do / Self-reported survey
People affected by fragrance say policies work only with purchasing rules for fragrance-free, low-emission products, staff education, better ventilation, and consequences for repeat violations, enforced like smoke-free rules.
Weak evidence: Participants' and authors' proposals; not tested as an intervention.
Source: Roy 2026 Link to this fact
What you can do / Hypothesis
Air a room or clean it instead of scenting it: non-chemical alternatives such as opening windows and better hygiene are the first step in Klaschka's ten-step hierarchy for reducing fragrance exposure.
Weak evidence: Expert recommendation; not tested in the paper.
Source: Klaschka 2020, Environmental Sciences Europe Link to this fact
What you can do / Review of other studies
If a child develops unexplained breast tissue, tell the doctor about every scented product the child uses or is near, including colognes, baby washes, hair products, and diffusers; stopping them is what the case reports did.
Weak evidence: Practical advice drawn from case reports, not a tested intervention.
Source: Hawkins 2020, Complementary Therapies in Medicine Industry-funded Link to this fact
What you can do / Self-reported survey
People who always or usually used a healthy-product app, read ingredient labels, or looked for eco-friendly labels used hair, skin, and beauty products with somewhat lower EWG hazard ratings, by up to half a point on a 10-point scale.
Weak evidence: Cross-sectional; the rating is built from the same labels, so it cannot see undisclosed fragrance chemicals; no exposure measured.
Source: Barrett 2025, Journal of Exposure Science & Environmental Epidemiology Link to this fact
Information, not medical advice. See also: myths we won’t tell you.