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.
Laws and loopholes / Other evidence
The review notes that rapidly excreted chemicals such as phthalates and bisphenol A are hard to assess from a few urine samples and that this imprecision might lead to underestimation of the true neurotoxicity risk.
Moderate evidence: Methodological point by the authors; it cuts toward under-detection, but it cannot show that an effect exists.
Source: Grandjean & Landrigan 2014, Lancet Neurology, The Lancet Neurology Link to this fact
Laws and loopholes / Other evidence
The Endocrine Society's 2015 statement urges that chemicals be safety tested for hormone-like activity at low doses before sale, warns that replacement chemicals can be sold without disclosure or adequate testing, and cites the BPA substitute BPS as acting like BPA in experiments.
Moderate evidence: Advocacy recommendation by a professional society, not a regulatory finding; BPA and BPS are not fragrance ingredients.
Source: Gore et al. 2015, Endocr Rev 36(6):593-602, Endocrine Reviews Link to this fact
Laws and loopholes / Other evidence
The 2016 TENDR statement said that when a toxic chemical is banned, manufacturers often swap in a similar, barely tested one, citing neonicotinoid and pyrethroid pesticides replacing OP pesticides, other halogenated and organophosphate flame retardants replacing PBDEs, and new phthalates replacing banned ones.
Moderate evidence: Examples are the authors' characterization, supported by emerging rather than established evidence for the replacements.
Source: Bennett et al. 2016 (TENDR Consensus Statement, EHP), Environmental Health Perspectives Link to this fact
Laws and loopholes / Other evidence
The 2016 TENDR statement asked regulators to treat evidence of neurodevelopmental toxicity of any single type (epidemiological, toxicological or mechanistic) as enough to trigger prioritization and some level of action, rather than waiting for unequivocal proof.
Moderate evidence: This is the advocacy-scientist group's policy stance, not a regulatory standard.
Source: Bennett et al. 2016 (TENDR Consensus Statement, EHP), Environmental Health Perspectives Link to this fact
Laws and loopholes / Other evidence
The TENDR authors noted that of the tens of thousands of chemicals on the US EPA inventory, nearly 7,700 are made or imported at 25,000 pounds or more a year and nearly 3,000 at over 1 million pounds a year, and that only a minority have been tested for neurotoxicity in adults and even fewer for effects on children's brain development.
Moderate evidence: Volume counts are as of 2006 and 2012 and are not current.
Source: Bennett et al. 2016 (TENDR Consensus Statement, EHP), Environmental Health Perspectives Link to this fact
Laws and loopholes / Other evidence
EU additives permitted before 20 January 2009 had to be re-assessed by EFSA under an evaluation program due by 20 January 2010, while the transfer of old additives to the new lists was a compliance review that did not include a new EFSA risk assessment.
Moderate evidence: Text states the obligation; our evidence base has not checked how far re-evaluation has progressed.
Source: EU Reg 1333/2008 Link to this fact
Laws and loopholes / Other evidence
OEHHA concluded the FDA acceptable daily intakes for synthetic food dyes were set from 1960s-80s toxicology studies not designed to detect behavior, and that in several animal studies effects appeared at or below the doses FDA used to set the ADIs (Red 3, Red 40, Yellow 5, Yellow 6).
Moderate evidence: A hazard-characterization judgment from a few rodent studies and one human dose-response trial; EFSA 2008 reached a different conclusion on the human trial data.
Laws and loopholes / Other evidence
Using NHANES 2015-2016 data, OEHHA estimated that children's typical food-dye intakes were below the FDA and JECFA ADIs for most dyes; the exception was Red 3, where hazard indices reached up to 15 against JECFA's 0.1 mg/kg/day.
Moderate evidence: Modeled intake from dye concentration data, few children in the highest cells; two-day-average rows in Table 6 look misprinted.
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
Skin allergy / Review of other studies
Benzalkonium chloride was the sixth highest-reacting allergen in a large retrospective patch-testing cohort, and caused contact dermatitis in 7-18.6% of patients using BAC-containing topical medicine for chronic leg ulcers.
Moderate evidence: Figures are from BAC used as a medical/topical antiseptic preservative, not from laundry or fabric-softener exposure.
Source: Peyneau 2022, Frontiers in Toxicology Link to this fact
Skin allergy / Measured in people or real products
In an industry (Procter & Gamble) study, adding the preservative glutaraldehyde to an experimental liquid fabric softener at 550 ppm (and, as a worst case, 5500 ppm) did not trigger allergic contact dermatitis in 16 subjects already known to be allergic to glutaraldehyde, whether exposed via undiluted product on skin, twice-daily open use for 8 days, or 14 days of wearing laundered T-shirts.
Moderate evidence.
Caveats
Funded by, and authored in part by, Procter & Gamble, the product's manufacturer; no independent (non-industry) replication of this specific formulation exists; results are specific to glutaraldehyde at these concentrations, not to laundry allergens generally.
Source: Weaver & Maibach 1977, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In the same study, 706 previously non-allergic subjects underwent repeated-insult patch testing with the glutaraldehyde-containing formulation (220 ppm applied dose for 340 subjects, 22 ppm for 366 subjects) and none developed new allergic contact dermatitis.
Moderate evidence.
Caveats
Industry-funded, single study, no independent replication; a repeated-insult patch test is a screening design meant to detect sensitization potential, not a guarantee that sensitization cannot occur in a much larger real-world population over longer exposure.
Source: Weaver & Maibach 1977, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
The authors calculate that the diagnostic dose used to confirm glutaraldehyde allergy in their sensitized subjects (10,000 ppm) was 18.2 times the glutaraldehyde concentration in their undiluted fabric-softener liquid (550 ppm) and 25,000 times the concentration reaching skin at recommended use (0.4 ppm in the laundry rinse water) — a large margin between the sensitizing/diagnostic dose and the realistic use dose.
Moderate evidence.
Caveats
This margin is specific to glutaraldehyde in this formulation; margins differ by orders of magnitude for other allergens, so it should not be generalized as a universal laundry-product safety margin.
Source: Weaver & Maibach 1977, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In the largest patch-test study of laundry-detergent-caused allergic contact dermatitis (738 referred dermatitis patients across 10 North American clinics), only 0.7% (5 patients) had a positive patch-test reaction to a 0.1% aqueous dilution of a liquid or granular laundry detergent, and the study's own authors believe even that rate is likely too high.
Moderate evidence.
Caveats
Study was funded by, and both detergents were supplied by, Procter & Gamble (the products' manufacturer); no independent (non-industry) replication exists; enrollment was a non-randomized convenience sample of patients already referred for suspected contact dermatitis, not a general population.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Of the only 2 patients whose detergent patch-test reaction could be further evaluated with dose-response testing and a blinded T-shirt wear test, one had a negative repeat test and use-test suggesting the original reaction was likely irritant, not allergic, and the other reacted equally to a fabric swatch laundered without any detergent as to one laundered with detergent.
Moderate evidence.
Caveats
Only 2 of the 5 original phase-I reactors could be re-tested (the other 3 were lost to follow-up, disqualified, or declined); conclusions about mechanism rest on this very small subgroup.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Belief that one's dermatitis is caused by laundry detergent (10.7% of 738 referred dermatitis patients, and 8.4% of consumers in an earlier mail survey) is far more common than allergy confirmed by patch testing (0.7% in this study).
Moderate evidence: Referred-clinic population, not general population; belief and confirmed-allergy rates come from different (though overlapping) study designs.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
None of the 5 patients who reacted to a detergent patch test also reacted to nickel or potassium dichromate, and only 1 of 5 had any fragrance-allergy marker positive (balsam of Peru, but not cinnamic aldehyde or fragrance mix) — among the 74 patients (10.0%) who did react to balsam of Peru, only 1 also reacted to a detergent mix, and that reaction was judged most likely irritant.
Moderate evidence.
Caveats
Small numbers (n=5 detergent reactors); does not rule out other, untested detergent components (e.g. surfactant impurities, enzyme residues) as the culprit in the small subset that may be truly allergic.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
At the 0.1% aqueous test concentration used for detergents, irritant or questionable reactions (11-12 patients, 1.5-1.6%) outnumbered clearly allergic-looking reactions (5 patients, 0.7%), showing these test concentrations already sit close to the irritant threshold, which limits how much higher a concentration could be used without generating false positives.
Moderate evidence.
Caveats
Irritant-vs-allergic classification at the borderline (1+) reaction grade is inherently subjective; the paper does not report a formal irritancy-threshold titration beyond the three dilutions tested.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Fragrance allergy caused by a deodorant correlated with a positive patch test to fragrance mix II or HICC (34.3% and 24.9% of deodorant-linked cases) more than to fragrance mix I or Myroxylon pereirae (28.2% and 12.7%), while scented lotion and shampoo correlated more with fragrance mix I and M. pereirae, suggesting deodorants are enriched for the specific chemicals in fragrance mix II rather than just containing more fragrance overall.
Moderate evidence: Correlational, single retrospective dataset; the paper does not independently verify deodorant formulations chemically, relying on prior surveys for that.
Source: Heisterberg 2011, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
Up to 30% of German deodorants in a given year contained at least one strong (Group I) fragrance allergen above the concentration that legally triggers labeling (0.001%).
Moderate evidence.
Caveats
Label-based count, not chemical analysis; the author cites independent chemical testing (Kantonslabor Basel) and Rastogi 2007a finding under-threshold allergens missed by label counts, so true prevalence may be higher.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
Skin allergy / Measured in people or real products
There was no significant difference in fragrance-allergen labeling between deodorants marketed for men and for women in Germany, even though a separate Danish clinical study found men have significantly more deodorant-caused fragrance allergic contact dermatitis than women.
Moderate evidence.
Caveats
Different countries and different measurements (label content vs. clinical outcome); the author explicitly says her data cannot explain the sex gap in allergy rates and only speculates that women may use deodorants, including neutral ones, more often.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
Skin allergy / Measured in people or real products
A history of contact dermatitis nearly doubled the odds of having a positive patch test (OR 1.9), but a history of atopic (eczema-type) dermatitis did not raise the odds at all (OR 1.0).
Moderate evidence.
Caveats
Cross-sectional self-report of dermatitis history, not confirmed diagnosis in all cases (about half were physician-confirmed); the OR rose to 2.4 when restricted to physician-confirmed contact dermatitis.
Source: Diepgen 2016 (EDEN), British Journal of Dermatology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In a 2019 survey of 65 best-selling US laundering products, fragrance/essential oils were the single most common potential contact allergen in every category: 66.7% of laundry detergents, 90% of fabric softeners, 75% of dryer sheets, and 58.8% of stain removers.
Moderate evidence.
Caveats
Ingredient-label declaration survey (n=65, non-random 2019 US best-sellers), not a chemical measurement or clinical study; 'fragrance' defined broadly to include 16 named essential oils and fragrance-mix components.
Skin allergy / Measured in people or real products
Methylisothiazolinone (MI), a preservative allergen, was the second most common allergen in laundry detergents overall (40%), and the single most common allergen in detergents labeled 'baby safe' (80%, 4 of 5) and 'free and gentle' (57.1%, 4 of 7).
Moderate evidence: Ingredient-label survey, not measured concentration or patch-test data.
Skin allergy / Review of other studies
Reviewing all available human, animal, and lab-dish evidence on 106 well-studied fragrance chemicals, the fragrance industry's own research institute found that 90 of them (85%) are capable of causing allergic skin sensitization at some dose — 6 strong, 23 moderate, 41 weak, and 26 very weak sensitizers — and only 10 had no evidence of sensitization at all.
Moderate evidence.
Caveats
Industry-authored (RIFM/Givaudan-consultant); the 106 materials were chosen specifically because in vivo data already existed on them, so this is not a random or representative sample of fragrance ingredients in commercial use, and none was rated the most severe ("extreme") category.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
Skin allergy / Review of other studies
Fragrance allergens differ enormously in how little exposure it takes to sensitize someone: prior published data cited in this paper's introduction describe known allergens that sensitize skin at under 1 microgram per square centimeter, while others need up to 10,000 micrograms per square centimeter — roughly a ten-millionfold range.
Moderate evidence: (background context the paper cites from earlier literature, refs 1 and 6, not a new measurement of this paper's own).
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In this industry dataset, the fragrance chemical methyl-2-nonynoate was rated a strong skin sensitizer with a human no-effect dose of only 24 micrograms per square centimeter of skin — among the lowest doses in the whole 106-chemical set — while a chemical like ethylene brassylate needed over 23,000 micrograms per square centimeter, nearly a thousandfold more, before it showed no allergic reaction.
Moderate evidence: Single industry dataset (RIFM Database plus published literature); NOEL is the maximum dose tested without inducing sensitization, not necessarily the true threshold.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.