Every fact on this site, with its evidence grade, its caveats, and a link to the source.
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.
Laws and loopholes / Review of other studies
After regulators banned BPA from baby bottles (EU 2011, Canada 2010, US FDA 2012-2013), manufacturers increasingly switched to substitute bisphenols such as BPS and BPF, which several human studies now also link to obesity and which are not proven to be safer than BPA.
Moderate evidence.
Caveats
Some studies of BPS/BPF exposure found no significant association with obesity, so the evidence is not unanimous, though none of the substitutes has been shown to be free of hormone-disrupting activity.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
Laws and loopholes / Review of other studies
Some salicylate compounds not approved by the FDA as sunscreen UV filters (e.g. butyloctyl salicylate, tridecyl salicylate) are added to mineral sunscreens under the ingredient category "stabilizer" rather than "UV filter" — a practice the review calls "doping" — letting manufacturers reduce the white cast of mineral formulations while avoiding the UV-filter regulatory category.
Moderate evidence: Single secondary citation for the labeling practice; not independently verified against product labels in this review.
Source: Hodge 2025, Marine Pollution Bulletin Link to this fact
Laws and loopholes / Review of other studies
Octocrylene, which sunscreen manufacturers adopted as an alternative after bans on oxybenzone in reef-protective jurisdictions (Hawaii, Key West Florida, Bonaire, Aruba, Palau, US Virgin Islands), is itself contaminated with benzophenone during manufacture and cannot be fully purified of it; it also undergoes a slow retro-aldol condensation reaction in the finished product that continuously regenerates more benzophenone as the sunscreen ages.
Moderate evidence: The underlying primary (Downs et al. 2021a) is not yet a evidence base source; treat the aging/regeneration mechanism as reported by this review pending that primary.
Source: Hodge 2025, Marine Pollution Bulletin Link to this fact
Laws and loopholes / Review of other studies
Global DEHP regulation is patchy and mostly national: Japan restricted DEHP in food packaging and childcare products in 2003, the EU in 2006, and Canada, the USA, and Australia later banned DEHP above set concentrations in children's products, but many countries still lack comprehensive DEHP regulation, and the exposure data analyzed in this study (2008) predate most of these rules.
Moderate evidence: Regulatory history as summarized in the paper's Discussion, not independently verified against primary legal texts.
Laws and loopholes / Government agency
A year before DOJ's case-by-case ruling, HUD's own internal guidance (Technical Guidance Memorandum 91-3, June 1991) told its regional Fair Housing investigators without qualification that "HUD presently recognizes MCSD as a 'handicap' under the Fair Housing Act" and that people with it "are also considered 'individuals with handicaps' under Section 504" — a more categorical stance than DOJ later endorsed.
Moderate evidence.
Caveats
This is an internal HUD policy memo, not a court ruling or DOJ's own position; DOJ's 1992 letter (the same file) declines to adopt this categorical framing, and nothing in our evidence base shows whether HUD later revised the memo.
Source: HUD TGM 91-3 (1991) Link to this fact
Laws and loopholes / Government agency
In a 1993 letter of findings, the US Department of Justice determined that a public entity is not required to prohibit employees from wearing perfume or other scented products, because that would not be a "reasonable" modification to personnel policy under ADA title II.
Moderate evidence.
Caveats
A technical-assistance letter states DOJ's own enforcement position; it is not a regulation or court ruling and does not bind courts. Addresses title II public access only, not title I employment accommodation.
Source: DOJ Civil Rights Division 1993 (TAL 383) Link to this fact
Laws and loopholes / Government agency
The same 1993 DOJ letter states that failing to adopt any access policy for individuals with environmental illness does not itself violate title II of the ADA, and that nothing in the ADA or its legislative history shows Congress meant to require public entities to regulate employees' use of scented products.
Moderate evidence: DOJ's own stated position at the time; not a court ruling, and DOJ explicitly declined to decide whether environmental illness meets the ADA's disability definition.
Source: DOJ Civil Rights Division 1993 (TAL 383) Link to this fact
Laws and loopholes / Government agency
In 1995 the US Department of Justice told a member of the public that under the ADA, it would 'usually' not be legally required for a medical facility to make its staff stop wearing fragrance to accommodate a patient with multiple chemical sensitivity, because fragrance use is treated as an employee's personal choice rather than a business policy.
Moderate evidence.
Caveats
Informal technical assistance to one inquirer, not a regulation or case law; DOJ's own letter states it 'does not constitute a legal interpretation of the statute' and 'is not binding on the Department.' 30 years old; predates the 2008 ADA Amendments Act's broadened definition of disability (a separate legal question this letter does not address).
Source: DOJ TAL605, 1995 Link to this fact
Laws and loopholes / Government agency
DOJ's letter answered a general, facility-wide framing of the question ('require their employees to refrain from wearing fragrances'), not the complainant's actual, narrower request for one department to go fragrance-free for one scheduled day.
Moderate evidence: DOJ's reply never analyzes the narrower request or any undue-hardship balancing; the mismatch is visible only by reading the attached correspondence alongside the reply.
Source: DOJ TAL605, 1995 Link to this fact
Laws and loopholes / Government agency
HUD's own Occupancy Handbook (4350.3 REV-1, Exhibit 2-6, June 2007) states that for a HUD-assisted housing resident with chemical sensitivity disorder, it is not an undue financial and administrative burden for the owner to give advance notice before cleaning common areas and to use nonchemical alternative cleaning methods where practical.
Moderate evidence.
Caveats
Binding operational guidance for HUD-assisted multifamily housing, not a court ruling; applies only to owner-controlled common-area cleaning, not to other tenants' or staff's personal fragrance/scent use, and 'where practical' is left case-by-case.
Source: HUD Occupancy Handbook 4350.3 REV-1, Exhibit 2-6 (2007) Link to this fact
Laws and loopholes / Government agency
The same HUD guidance states it would be an undue administrative burden for a HUD-assisted housing owner to survey every tenant in a building for what chemicals they use to clean their own units and when, and compile that into a weekly report for a chemically sensitive resident.
Moderate evidence.
Caveats
HUD's stated reason is administrative capacity ('could not be handled by the existing staff'), not cost; this refusal is specific to a full building-wide, ongoing, per-tenant monitoring and reporting scheme, not to lesser accommodations.
Source: HUD Occupancy Handbook 4350.3 REV-1, Exhibit 2-6 (2007) Link to this fact
Laws and loopholes / Government agency
The EU sets a specific migration limit of 0.6 mg/kg for benzophenone as a plastics additive (Directive 2002/72/EC) and caps its deliberate use as a flavoring at 0.5 mg/kg in beverages and 2 mg/kg in foods generally (Council of Europe, 2000), while US reported flavoring-use levels range from 0.57 to 3.27 ppm across beverage, baked-good, and frozen-dairy categories.
Moderate evidence.
Caveats
Regulatory limits describe permitted/reported levels, not measured exposure; actual food-content surveys cited elsewhere in the monograph found some samples above these reference levels (e.g., 7.3 mg/kg in one high-fat chocolate).
Source: IARC 2013 Link to this fact
Laws and loopholes / Government agency
The ACCC's 2019 consultation paper compared Australia's cosmetics labeling rules against the EU, New Zealand, US, and ISO standards in detail and identified nanomaterial disclosure and additional label fields (expiry date, batch number, responsible person, product function) as the substantive gaps worth reforming — fragrance-allergen disclosure was not raised anywhere in the paper as an issue, gap, or reform option.
Moderate evidence.
Caveats
Absence of a topic in a policy document is evidence the ACCC did not identify it as an issue at that time; it is not proof the ACCC considered and affirmatively rejected an allergen list.
Source: ACCC 2019 Link to this fact
Laws and loopholes / Review of other studies
The Endocrine Society calls for EDC regulation generally to be hazard-based and precautionary rather than risk/threshold-based, the same hazard-based approach the EU currently applies only to pesticides and biocides and not to cosmetics, toys, or food-contact materials.
Moderate evidence.
Caveats
The statement itself does not discuss the EU's cosmetics carve-out or recommend extending hazard-based regulation to cosmetics specifically; the link to the EU's two-track policy is this evidence base's inference, not the Society's stated position.
Source: Endocrine Society 2025 Link to this fact
Laws and loopholes / Other evidence
MoCRA's mandated talc-in-cosmetics asbestos testing-methods rule was proposed by FDA in December 2024 and then withdrawn in November 2025.
Moderate evidence: Based on FDA's own overview page's link labels and dates, not on the Federal Register documents' full text, which were not separately captured in this batch.
Source: FDA MoCRA overview page, accessed 2026-09-28 Link to this fact
Laws and loopholes / Government agency
The New Zealand cosmetics standard amendment taking effect 1 January 2026 (decision APP204297, dated 25 January 2024) covers the group standard's scope, Schedules 4 to 8, and a PFAS phase-out, according to the superseded document's own regulatory-history table — labeling requirements are not named as part of what changed.
Moderate evidence.
Caveats
This is a secondhand summary from the pre-amendment document's own regulatory-history table, not the amendment's full text; the actual current EPA document was not fetched or read in this ingest.
Source: Cosmetic Products Group Standard 2020 (NZ, HSR002552, consolidated to 2025) Link to this fact
Laws and loopholes / Self-reported survey
MCS is legally recognized as a disability in Canada, but in a national survey most people with MCS who asked for a workplace or housing accommodation before the pandemic (85% of 119) were refused at least once (the paper's own figure: 'at least 78%').
Moderate evidence.
Caveats
Self-reported, cross-sectional, community-based convenience sample of 119 recruited substantially through an MCS advocacy charity's own channels (ASEQ-EHAQ, which also funded the study and paid some authors); over-represents Quebec; likely under-represents the most severely affected.
Source: Diallo 2026 Link to this fact
Laws and loopholes / Self-reported survey
Fear of retaliation, stigma, and losing support increasingly kept Canadians with MCS from even requesting an accommodation: the share who did not request one nearly tripled, from 15% before the COVID-19 pandemic to 42% after, and every listed fear-based reason for not requesting increased over the same period.
Moderate evidence.
Caveats
Self-reported, n=119 (18 and 50 respondents gave reasons in the two periods respectively), multi-select so percentages exceed 100%; cannot separate deterrence from reduced need (e.g., remote work) as the cause.
Source: Diallo 2026 Link to this fact
Laws and loopholes / Government agency
As of 2019, FDA's own proposed sunscreen rule found insufficient data to confirm avobenzone, oxybenzone, and octocrylene as 'generally recognized as safe and effective' sunscreen actives — of 16 monograph ingredients, only the mineral filters zinc oxide and titanium dioxide had cleared that bar — while the codified US sunscreen regulation (21 CFR Part 352) still lists all of them as permitted, and that Part has carried a 'stayed indefinitely' notice since 2003-2004.
Moderate evidence.
Caveats
Reflects the regulatory status as of the 2019 trial and the 2023 CFR codification captured in this evidence base; a finalized monograph rule issued after either date would supersede this.
Source: Matta 2019, JAMA Link to this fact
Laws and loopholes / Measured in people or real products
A 2026 primary measurement study of cosmetic spray products concluded that current cosmetic safety assessment lacks any framework for inhalation exposure, stating there is an urgent need for regulatory frameworks targeting inhalation exposure from cosmetic sprays.
Moderate evidence.
Caveats
This is the authors' stated policy conclusion, not a dose-response or health-outcome finding; it extends, but does not resolve, our existing C178 (no inhalation branch in fragrance/cosmetic safety review processes).
Source: Dai et al. 2026, ACS Environmental Au Link to this fact
Laws and loopholes / Government agency
EU law now states, as a general principle, that fragrance substances able to transform into known contact allergens via air oxidation or bioactivation ('prehaptens and prohaptens') should be regulated the same as the allergens they become — but this 2023 amendment does not apply a specific hydroperoxide limit or peroxide-value restriction to limonene or linalool, the two chemicals most discussed in the oxidized-fragrance-allergen literature.
Moderate evidence.
Caveats
Recital 7 states the principle in general terms; reading the Annex directly shows no limonene- or linalool-hydroperoxide entry and no peroxide-value cross-reference for either chemical (only the new Pinene entry is linked to an existing peroxide-value restriction).
Source: Regulation (EU) 2023/1545 Link to this fact
Laws and loopholes / Government agency
The EU regulation's own recital states that only 24 fragrance allergens required individual labeling before the 2023 amendment, not the commonly cited figure of 26.
Moderate evidence.
Caveats
The 2-substance gap between the EU's legal '24' and the SCCS's own scientific classification baseline of 26 (per Kumar 2020) is not explained in the regulation's text; a plausible but unconfirmed mechanism is that 1-2 of the original 26 were later banned outright from cosmetics by a separate EU restriction.
Source: Regulation (EU) 2023/1545 Link to this fact
Laws and loopholes / Measured in people or real products
None of the 14 air fresheners NRDC tested in 2007 disclosed phthalates on the product label, consistent with the wiki's broader finding that no US law requires full fragrance-ingredient disclosure on consumer products.
Moderate evidence: Observation from this report's own 14-product sample, not an independent legal survey.
Source: NRDC 2007, Clearing the Air Link to this fact
Laws and loopholes / Other evidence
None of the 10 NYC nail salons studied in 2017 had installed the local exhaust ('source capture') ventilation at manicure and pedicure stations that New York State's own nail-salon ventilation regulation requires, even though all 10 had general HVAC and 7 were running it.
Moderate evidence: The regulation's full compliance deadline was 2021 (this study ran in 2017), so this documents a pre-deadline baseline, not a current violation.
Source: Pavilonis, Roelofs & Blair 2018, Journal of Occupational and Environmental Hygiene Link to this fact
Laws and loopholes / Measured in people or real products
New York State's 2014 ban on methyl methacrylate (MMA) in nail salons appears reflected in 2021 air measurements: NY salons showed higher ethyl methacrylate (EMA, the substitute, median 0.55 ppb) than MMA (median <0.09 ppb), while New Jersey salons, with no such ban, showed the opposite pattern (MMA median 1.77 ppb vs EMA median 0.12 ppb).
Moderate evidence.
Caveats
The study did not examine nail-product ingredients directly, so the MMA/EMA state pattern is the authors' inference from a state-law difference, not a confirmed causal test; single small pilot study.
Source: Han et al. 2022 Link to this fact
Laws and loopholes / Measured in people or real products
FDA's own expanded absorption data — now covering 6 sunscreen active ingredients across two trials, all exceeding the agency's 0.5 ng/mL toxicology-waiver threshold — has not been reflected in the codified US sunscreen monograph (21 CFR Part 352), which has remained stayed since 2003/2004 and still permits these same ingredients at their original concentrations.
Moderate evidence.
Caveats
This is a regulatory-timing gap, not evidence the ingredients are unsafe; the paper itself frames exceeding the threshold as triggering a request for more toxicology data, not a safety conclusion.
Source: Matta 2020, JAMA Link to this fact
Skin allergy / Review of other studies
About 1 in 22 European adults (4.5%) tested positive to at least one of six fragrance-related patch-test markers (2008-2011); single fragrance markers pick up 1-3%, and up to 16% of patients referred for patch testing react.
Moderate evidence.
Caveats
The 4.5% is described as a six-marker union including non-fragrance markers (colophonium, sesquiterpene lactones), with no clinical-relevance criterion. Both EDEN primaries — Diepgen 2015 (src-2015-fragrance-contact-allergy-five-european-countries) and Diepgen 2016 (src-2016-prevalence-contact-allergy-general-population-european-regions) — have now been read in full and neither prints this six-marker composite. Diepgen 2015's own composites are 4.1% (raw, five markers, no colophonium) and 4.5% (FM I/FM II single-ingredient union, no colophonium); Diepgen 2016's own fragrance composite (FM II+HICC+sesquiterpene lactone mix) is 2.2%. Colophonium is not tested as a fragrance marker in either EDEN paper. de Groot 2020 (the earlier, most-cited fragrance review; src-2020-fragrances-contact-allergy-other-adverse) gives the same '4.5%' figure but explicitly as the review author's own extrapolation ('The author of this article estimates that up to 4.5%…'), reasoned from EDEN's marker gaps and hydroperoxide sensitization rates, not as a cited six-marker composite from any single study. The number may have propagated through the review literature as an inference that later reads as a hard statistic; still unverified against a primary composite.
Source: Sukakul 2024, Acta Dermato-Venereologica Industry-funded Link to this fact
Skin allergy / Lab study (cells or chemistry)
In the fragrance industry's own reference set of 62 fragrance ingredients, 19 are rated moderate or strong skin sensitizers, meaning chemicals capable of causing allergy.
Moderate evidence: Industry (RIFM) weight-of-evidence categories; lab and animal data, not human exposure.
Source: Lee 2024, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In patch tests on 61 people, fresh limonene and linalool did not irritate skin, but after air exposure (oxidation) both did; oxidized limonene at 20% caused strong redness (average 7.3 of 9 vs near 0 fresh).
Moderate evidence: RIFM-funded; test concentrations far above product levels.
Source: Bråred Christensson 2009, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Review of other studies
In about half of oxidized limonene/linalool allergy cases, doctors could link the allergy to products the patient actually used.
Moderate evidence.
Caveats
Whether a given product actually reaches the reaction-triggering hydroperoxide level depends heavily on its age/storage: industry data found Lim-2-OOH below 5 ppm in most recalled fine fragrances tested, versus ~2900 ppm in an experimentally aged orange oil after 1 year of dark storage (Bennike 2019). The strongest direct test of "linked to products used" now undercuts it rather than supporting it: Natsch 2019 chemically tested 28 products donated by dermatology patients via the same GEIDAC network this review draws on, including 11 from patients already confirmed patch-test-positive to oxidized limonene/linalool who specifically named the donated product as their suspected trigger, and found zero detectable hydroperoxide in any of them (confirmed by two independent LC-MS methods). Clinical "linkage" judgments based on patient history and declared product content do not survive chemical confirmation in this sample, so the claim moves from a plausible clinical inference to one now directly (though not exhaustively) tested and not supported. Natsch 2019 (industry-funded) found no hydroperoxide in 28 products donated by patients, including 11 from patients allergic to oxidized limonene/linalool. That questions whether the named product is the actual source, but it can't falsify the clinicians' relevance assessments; the exposure route remains unexplained. 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.
Skin allergy / Measured in people or real products
Allergy to these two scent chemicals rose significantly over the eight years studied (2013-2020).
Moderate evidence: Patch-test chamber system changed in 2018, which may affect the trend.
Skin allergy / Measured in people or real products
Women were affected about 1.5 to 2 times as often as men, and these patients were younger on average than people allergic to other fragrance ingredients.
Moderate evidence: Likely reflects product-use patterns; clinic population.
Skin allergy / Review of other studies
Benzyl alcohol, a fragrance allergen, is also a preservative in common prescription creams and injections, including steroid, antifungal (clotrimazole) and antibiotic (mupirocin) creams, so fragrance-allergic patients can meet it in their medicines.
Moderate evidence: Based on case reports; no prevalence of benzyl alcohol allergy given.
Skin allergy / Lab study (cells or chemistry)
Skin converts part of cinnamyl alcohol into cinnamal, the stronger allergen: on human skin samples, about 4% of applied cinnamyl alcohol became cinnamal within a day.
Moderate evidence: Excised human skin, neat material, occluded, 24 h (Smith 2000); single study.
Source: RIFM Expert Panel 2005, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Allergy to one rose ketone tends to mean allergy to its relatives: all 3 volunteers sensitized to delta-damascone reacted to 0.1% cis-beta-damascone on cross-challenge.
Moderate evidence: N=3; from an unpublished RIFM report.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Review of other studies
Benzyl salicylate, one of the most widely used fragrance chemicals (about 2,500 metric tons a year worldwide in 2007), caused skin allergy in the fragrance industry's own tests, and the industry's standards body IFRA restricts how much may be used.
Moderate evidence: Human maximization 3/50 positive at 20%; repeat-insult patch tests were negative (0/101 at 15%); LLNA EC3 1.5-2.9% in mice. Industry-funded review of largely unpublished reports.
Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Standard allergy screening misses a large share of fragrance allergy: in one UK clinic 42% of patients allergic to at least one of the 26 EU-labeled fragrance chemicals tested negative on the standard fragrance markers, and about 4 in 10 people who reacted to their own perfume or deodorant were negative on the screen.
Moderate evidence.
Caveats
Comparator-dependent: Sukakul 2022 found ~10% missed when comparing fragrance mixes with their own ingredients (abstract-sourced). The Mann 2014 primary, now read in full (not just its abstract), confirms 203 patients reacted to any of the 26 EU fragrances and only 117 (57.6%) also reacted to a baseline marker = 42.4% missed; Mann's own Discussion states this as "40.6%" in one sentence, a small internal inconsistency in the primary (Results math gives 42.4%). More importantly, Mann's own paper reports a similarly-designed Danish study (Heisterberg 2011, n=1,508, also routine testing of all patients with the same 26 fragrances) that found only 15.6% missed — a ~2.5-fold discrepancy the authors attribute only partly to higher test concentrations and a different patient population, not fully resolved. The own-product figure (41%/45%) is from a different study (Uter 2007), not Mann.
Skin allergy / Measured in people or real products
Some fragrance chemicals now banned from EU cosmetics sensitized almost every volunteer in the industry's own tests: diethyl maleate 25 of 25, dihydrocoumarin 25 of 25, alantroot oil 23 of 25.
Moderate evidence: Maximization test is deliberately exaggerated (irritant pre-treatment, occlusion, ~10x use level); substances are banned and mostly left perfumery before 2000.
Skin allergy / Measured in people or real products
Essential oils are made largely of the same chemicals labeled as fragrance allergens: supplier data sheets give sweet-orange oil about 95% limonene, lavender oil about 40% linalool, and palmarosa oil up to 84% geraniol.
Moderate evidence: Composition from supplier safety data sheets, which vary between suppliers (cypress oil limonene 5-7% vs 14%); not measured in finished products.
Source: Klaschka 2016, Environmental Sciences Europe Link to this fact
Skin allergy / Measured in people or real products
Half of best-selling US body moisturizers (87 of 174) list "fragrance" on the label, making it the most common potential skin allergen in them, ahead of parabens (75) and vitamin E/tocopherol (74).
Moderate evidence: Literal-word count, a lower bound for fragranced products; 2016 US online best-sellers.
Skin allergy / Animal study
Left open to air, lavender oil became about 8 times more potent as a skin sensitizer in mouse tests (EC3 36% fresh, 4.4% after 45 weeks).
Moderate evidence: Mouse LLNA, groups of 3-4 mice, one 45-week sample; aged oil reached 'moderate', not 'strong', potency; open-flask lab exposure.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
After 10 weeks of air exposure, lavender oil contained about 3.3% linalyl acetate hydroperoxides and 0.5% linalool hydroperoxides, the kind of oxidation products behind the commonest fragrance allergies in European clinics.
Moderate evidence: Open-flask lab exposure (upper bound); retail bottles not measured.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
The two commonest fragrance allergens on Danish children's cosmetics, limonene (22% of fragranced products) and linalool (18%), are not in the standard European patch test series; they become strong allergens when they oxidize in air.
Moderate evidence: Frequencies are label presence; oxidation not measured in these products (relayed from hydroperoxide literature); some clinics now add the hydroperoxides to their baseline.
Skin allergy / Lab study (cells or chemistry)
Oxidized linalool and oxidized limonene, among the most common fragrance allergens found in European skin clinics, are not in the 312-chemical dataset these safety models were built on.
Moderate evidence: Clinic prevalence figures for oxidized terpenes come from a separate paper (Sukakul 2022), not this one.
Source: Natsch 2015, Toxicological Sciences Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Sensitivity to cinnamal varies enormously between allergic people: this study measured a 1000-fold range in the concentration needed to trigger a reaction.
Moderate evidence: Range measured in 9 patients only.
Source: Bruze et al. 2003, Journal of the American Academy of Dermatology Link to this fact
Skin allergy / Measured in people or real products
Whether a specific limonene-scented product is likely to trigger a reaction in an allergic person depends heavily on how oxidized/aged it is: an experimentally aged orange oil's allergenic hydroperoxide content rose nearly 6-fold (500 to 2900 ppm) after a year in storage, while some real aged fine fragrances tested by industry stayed below the reaction-triggering range.
Moderate evidence: The storage/aging data come from a separate cited experimental study, not this paper's own clinical subjects, and cover only one product type (orange oil).
Skin allergy / Measured in people or real products
Only 15% of people with a borderline ('doubtful') patch-test reaction to limonene hydroperoxides went on to react when exposed repeatedly to a realistic dose, a rate no different from people with no allergy at all.
Moderate evidence: Small subgroup (13 people, 2 positive); underpowered to rule out that some fraction of doubtful reactors are truly allergic.
Skin allergy / Measured in people or real products
In a survey of 187 US pediatric personal-care products, preservatives (57.8% of products) were a more common source of contact allergens than fragrance (29.4%), even though the products were being screened specifically for hypoallergenic/fragrance-related marketing claims.
Moderate evidence.
Caveats
Category-level result from one survey; the two categories are not mutually exclusive at the product level (a product can carry both preservative and fragrance allergens), and the finding has not been replicated in a different pediatric sample.
Source: Hamann 2015, Journal of Allergy and Clinical Immunology Link to this fact
Skin allergy / Measured in people or real products
A standard fragrance patch-test panel (Fragrance Mix I/II) misses about 1 in 5 cases of medication-caused fragrance allergy, because the reaction is to an individual essential oil or ingredient not covered by the mixes.
Moderate evidence.
Caveats
24/127 (19%) in one clinic's iatrogenic-ACD case series (Belgium, 1978-2008); denominator is a clinic-referred population, not a general-population estimate; different populations give different "missed" rates (Mann 2014 ~42% vs 26 EU allergens; Sukakul-derived ~10% vs FM ingredients).
Skin allergy / Measured in people or real products
For two common fragrance chemicals, trans-2-hexenal and methyl-2-nonanoate, the mouse test underestimated true human skin-sensitizing potency by 26- to 42-fold — the error direction that could make an industry safety limit too permissive rather than too strict.
Moderate evidence.
Caveats
Only 2 of 57 chemicals in the dataset show this specific magnitude of underestimation; industry-funded (RIFM/DABMEB); the human NOEL itself is a floor, not a measured breakpoint, since dosing was not escalated to a positive result for ethical reasons.
Source: Api, Basketter & Lalko 2014, Cutaneous and Ocular Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Women's fragrance contact allergy rates are roughly double men's.
Moderate evidence.
Caveats
Ratio varies by marker from about 1.5x (fragrance mix I) to 2.1x (HICC), not a uniform 2x; a pooled meta-analysis (Alinaghi 2018) finds fragrance allergy closer to sex-neutral overall.
Source: Diepgen 2015 (EDEN), British Journal of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
A Givaudan-funded study that chemically measured 39 real aged fragrance products found linalool hydroperoxide levels far below the dose shown to trigger a reaction in already-allergic patients, roughly 180 times lower on average.
Moderate evidence: Industry-funded (Givaudan), single study, not independently replicated; only two product categories tested (hydroalcoholic fine fragrance, antiperspirant/deodorant).
Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact
Skin allergy / Other evidence
The fragrance industry's original 1976 evidence for aldehyde 'quenching' (that a companion terpene or alcohol stops citral, cinnamic aldehyde, or phenylacetaldehyde from causing skin sensitization) was a single, unreplicated human maximization test per mixture with no subject numbers reported, and the paper's own data are internally inconsistent: cinnamon bark oil sensitized despite being one of the paper's three 'protective natural oil' examples, and cinnamic aldehyde + eugenol sensitized at a 2.5:1 ratio where 1:1 had not.
Moderate evidence.
Caveats
No subject number (n) is stated anywhere in the paper for any test; no statistics, blinding, or control arm distinct from the aldehyde-alone condition; the author calls the findings preliminary and says further study was 'now in the second year.'.
Source: Opdyke 1976 (RIFM), Food and Cosmetic Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In a UK study that routinely patch tested 1,951 eczema patients with both the standard fragrance-allergy screen and all 26 individually EU-labeled fragrance chemicals, 42% of the patients allergic to at least one of those 26 chemicals would have been missed if only the standard screen had been used.
Moderate evidence.
Caveats
Single UK tertiary-referral clinic (n=1,951), not a general-population figure. A comparably-designed Danish study using nearly the same routine-testing protocol found only 15.6% missed, so this exact percentage does not generalize across clinics without qualification.
Skin allergy / Measured in people or real products
The two fragrance mixes used in standard allergy testing (FM I and FM II) each miss roughly half of the people who are allergic to their own listed ingredients: only 58% of those reacting to an FM I ingredient, and only 52% of those reacting to an FM II ingredient, reacted to the mix itself.
Moderate evidence: Single UK clinic (n=1,951), not independently replicated at this exact figure.
Skin allergy / Measured in people or real products
A large fragrance-industry study tested 104 real consumer products, including creams, lotions, and antiperspirants, for the allergenic chemicals that form when the scent chemicals limonene and linalool oxidize in air, and found almost none of them: 96% of products had no detectable hydroperoxide, and the one confirmed positive was hundreds of times below the dose known to trigger a reaction.
Moderate evidence: Industry-funded (IDEA consortium: Givaudan, Firmenich, IFF, IFRA), not independently replicated by a non-industry group.
Source: Natsch 2019, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Even when scientists chemically tested the actual products that people with a confirmed allergy to oxidized limonene or linalool blamed for their skin reaction, none of the 28 products tested (11 from confirmed allergy patients) contained a detectable amount of the allergenic chemical.
Moderate evidence.
Caveats
Small sample (28 products, 11 from confirmed patch-test-positive patients) relative to the >22,000-patient clinical literature on this allergy; industry-funded, not independently replicated; other exposure routes (skin-surface formation after application, airborne deposition) are untested.
Source: Natsch 2019, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Concentrations of hydroxycitronellal found in some 'natural' perfumes (up to 6.04%) exceeded the concentration shown to sensitize 36% of healthy volunteers in repeated-insult patch testing (5%), and were also well above the fragrance industry's own 1996 recommended maximum (equivalent to about 1% in the finished product).
Moderate evidence.
Caveats
Single-study 1996 patch-test-sensitization citations (Ford & Api 1988; Suskind 1992) for the 5%/36% figure, not independently verified in this evidence base; product concentration is not the same as measured consumer exposure dose.
Skin allergy / Review of other studies
Patch testing is the diagnostic gold standard for allergic contact dermatitis, including fragrance allergy, but access to it is uneven: in the US, African American and lower-income patients are referred for and receive patch testing less often than White and higher-income patients, and rural patients have reduced access and longer symptom duration.
Moderate evidence.
Caveats
The disparity claims are cited from secondary/administrative-claims sources within a narrative review, with no effect size given by this paper itself; a distinct, upstream complement to the post-diagnosis label-comprehension gap in Noiesen 2007 (see contradictions C284 extension).
Source: Aristizabal-Torres 2025, JAAD Reviews Link to this fact
Skin allergy / Measured in people or real products
Among all detergent types studied, laundry (textile) detergents had both the highest share of products naming a fragrance allergen (50.0% of 270 products) and the highest average number of named allergens per product (1.7) — ahead of dish soap, glass cleaner, toilet cleaner, and dishwasher detergent.
Moderate evidence: Named-on-label only, not measured concentration or skin dose; German 2015 sample.
Source: Wieck 2018, Regulatory Toxicology and Pharmacology Link to this fact
Information, not medical advice. See also: myths we won’t tell you.