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.
Hidden ingredients / Animal study
The regulatory endocrine dossier on linalool tested 99.7%-pure, freshly handled material, not the air-oxidized linalool that forms in an opened bottle and that accounts for almost all of linalool's known allergy risk. Nobody has tested whether oxidized linalool is hormonally active.
Moderate evidence: This is standard and correct practice for a REACH dossier; it is a limit on what the result covers, not a flaw in the study.
Source: Hareng 2024, Archives of Toxicology Industry-funded Link to this fact
Hidden ingredients / Other evidence
Several flavor chemicals in this review (menthol, carvone, camphor, borneol, terpineol, ionones, damascones and the musks muscone, and civettone) are also fragrance materials, but the FEMA review assesses them only as swallowed food ingredients; it gives non-oral data 'less weight' and has no inhalation or skin-allergy assessment.
Moderate evidence: The paper says some inhalation data may substitute when flavor exposure is far smaller than inhaled exposure; it does not claim any airborne or skin risk from these substances.
Source: Adams 1996, Food and Chemical Toxicology Industry-funded Link to this fact
Hidden ingredients / Other evidence
Textile-dye allergy often looks atypical (purpuric, hives-like, prurigo-like, eczema away from skin contact points) and a high index of suspicion is needed, so it can be missed.
Moderate evidence: Based on case reports and case series; no frequency of atypical presentations across all patients.
Source: Malinauskiene 2013, Contact Dermatitis Link to this fact
Hidden ingredients / Animal study
In a Dutch government study, isoeugenol was the only one of five skin-allergy fragrance chemicals to stimulate the lymph nodes of mice that breathed it (about 7-fold more cell growth after 6 hours a day for 3 days), while limonene and linalool did not.
Moderate evidence.
Caveats
Mice (6 per group), one lab, nose-only at 75 mg/m3, an unvalidated assay tested mostly on strong sensitizers; a hazard signal, not human disease. Government-funded (NVWA), no industry money declared.
Source: ter Burg 2014, Inhalation Toxicology Link to this fact
Hidden ingredients / Other evidence
Methylisothiazolinone allergy became an epidemic after MI alone was approved as a preservative at higher concentrations in the early 2000s, and a patch test with only the MCI/MI mix can miss it; hidden sources include moist toilet paper, makeup-remover wipes, paint, and homemade slime.
Moderate evidence: Narrative review; the 'up to 8%' MCI/MI contact-allergy figure has no stated population in the text.
Source: Militello 2020, Dermatologic Clinics Link to this fact
Hidden ingredients / Other evidence
The flavor panel's food assessment is silent on skin allergy, inhalation, and cosmetic use: the words allergy, sensitization, and atranol do not appear in the assessment, and the abstract excludes 'dietary supplements or any products other than food'; so food-GRAS status of oak moss or jasmine says nothing about their behavior as fragrance allergens.
Moderate evidence: Absence of a topic in an industry review is not evidence of harm; it is a scope limit the paper states for supplements only by name and by 'any products other than food'.
Source: Guengerich 2026 (FEMA Expert Panel), Food and Chemical Toxicology Industry-funded Link to this fact
Hidden ingredients / Other evidence
The hydroperoxides that cause this allergy are not listed on labels, so patients can only look for limonene and linalool, two of the 26 EU-declarable fragrance allergens.
Moderate evidence: Authors' statement about labeling in the EU; limonene and linalool on a label show the parent chemical, not whether any hydroperoxide is present.
Source: Dittmar & Schuttelaar 2019, Contact Dermatitis Link to this fact
Hidden ingredients / Review of other studies
Sulfites, a preservative that can cause skin allergy, are found in many medicines you would not suspect: topical steroids, antibiotics, antifungals, hemorrhoid creams, local anesthetics, catheter gel, and 3.8% of 264 ophthalmic medications checked.
Moderate evidence: Narrative review; the 3.8% figure comes from a single analysis of prescription eye products, and the other medicines are case reports, not prevalence.
Source: Choi 2024, Cutis Link to this fact
Hidden ingredients / Other evidence
Three studies found 28%, 17% and 23% of skin creams labeled incorrectly against the specific legislation, and 46% of allergic participants had difficulty reading cosmetic labels, so an ingredient list does not guarantee that a preservative allergy can be avoided.
Moderate evidence: Older, small Scandinavian and Korean product surveys; the review does not say what the errors were.
The industry / Lab study (cells or chemistry)
The fragrance industry's own data show its main explanation for how fragrance chemicals cause allergy doesn't cover most of them: 34 of 62 ingredients (55%) sensitize despite having no predicted protein-binding alert.
Moderate evidence.
Caveats
Structural-alert software limitation; metabolic activation explains some. Roberts & Api 2018 (different 57-chemical fragrance dataset, no direct overlap confirmed with this claim's 62-chemical set) adds two further indirect-activation routes the alert software here evidently does not capture — slow autoxidation of tertiary allylic/benzylic C-H compounds to allergenic hydroperoxides/epoxides, and a proposed bio-sulfation route for benzylic alcohols — which could explain part of the unexplained 55% for chemicals with those structural motifs. The same paper separately proposes that some LLNA-positive, alert-free fragrance chemicals (hexyl/benzyl salicylate) may be LLNA false positives rather than true sensitizers at all, which would pull in the opposite direction (shrinking, not explaining, the true no-mechanism fraction) if any such chemicals are present in this claim's 62-ingredient set — not checked here, so the net effect on the 55% figure is unresolved and the grade is left unchanged.
Source: Lee 2024, Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
Those models underestimated allergy potency by more than fivefold for 18% of the 188 chemicals tested, and more than tenfold for 11%.
Moderate evidence.
Caveats
Prediction error, not a safety-limit error; worst outliers are non-fragrance chemicals. Natsch 2023 (same author, human-anchored retraining) shows this outlier structure is not simply an artifact of fitting to mouse data: only 6/139 chemicals (4.3%) shift by more than 3.3-fold when the same models are retrained against human-anchored potency values instead of LLNA.
Source: Natsch & Gerberick 2022, ALTEX Industry-funded Link to this fact
The industry / Industry source
The industry's standard safety package for a fragrance ingredient in 1994 covered acute poisoning and skin effects (irritation, allergy, sun reactions); breathing it in was not tested, because the industry judged inhalation 'not a route of toxicological concern'.
Moderate evidence.
Caveats
As of 2024, RIFM/Creme Global's aggregate exposure model (Lee 2024) does now include a full inhalation-TTC branch across ~3,000 fragrance ingredients (99% below the inhalation TTC), so the industry itself has since closed this specific 1994 scope gap methodologically — though whether ingredients assessed only under the older dermal-only dossiers were individually revisited is not stated. The gap's closure was gradual, not a single 2024 event: Comiskey et al. 2017 (Phase 2 of the same RIFM/Creme model) added the model's first-ever inhalation branch, 23 years after this 1994 dismissal, but only for air-care and personal-care spray products — household cleaning and laundry products were explicitly still excluded and named as future work in 2017, closing only in the 2024 paper.
Source: Ford 1994 (RIFM) Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
When the same lab-dish tests that replace animal testing are checked against real human allergy-test panels instead of mouse data, they explain only about 32-45% of how strongly a chemical causes allergy in people, and the mouse test itself does barely better, explaining only 43%.
Moderate evidence: The strictly-human comparison dataset (n=62) is small and the author flags it as biased/non-representative; a larger human dataset might do better.
Source: Natsch 2023, ALTEX Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
Neither the animal test nor its lab-dish replacements are strong predictors of real human allergy thresholds; they are about equally weak, shown independently in 2015 and again in 2023.
Moderate evidence: Both comparisons reuse overlapping historical human patch-test literature (HRIPT/HMT), not independent new human data.
Source: Natsch 2023, ALTEX Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
Whether a chemical is irritating to cells in a dish, not just whether it reacts with proteins, drives a lot of the mouse allergy test's readout in ways that don't reflect real human allergy.
Moderate evidence: Statistical inference from regression coefficients across three chemical subsets, not a direct mechanistic experiment.
Source: Natsch 2023, ALTEX Industry-funded Link to this fact
The industry / Lab study (cells or chemistry)
The fragrance industry's own 2007 safety review of benzyl salicylate assessed allergy, toxicity, and cancer risk in detail but never tested it for hormone-like activity at all; the first test came two years later, from an independent lab with no fragrance-industry funding.
Moderate evidence.
Caveats
The independent test found only a weak, partial effect, at concentrations well above the industry's own worst-case exposure estimate, so this closes a testing gap rather than reversing the 2007 review's 'safe as used' conclusion.
Source: Charles & Darbre 2009, Journal of Applied Toxicology Link to this fact
The industry / Measured in people or real products
In RIFM's own comparison of 57 fragrance chemicals, the mouse test used to set fragrance skin-allergy safety limits agreed with real human sensitization thresholds within about 3-fold for 76% of the chemicals tested, but was off by up to nearly 800-fold for others, including hexyl and benzyl salicylate.
Moderate evidence.
Caveats
Single paper/author group (RIFM staff plus an industry consultant), though a large (57-chemical), systematically protocolled primary dataset; the authors themselves call the outlier groups 'an alert for consideration, rather than… a general rule' given only 7 materials populate each. Corroborates, from a different metric and era, the LLNA-human accuracy gap C230 documents for the newer non-animal replacement tests.
Source: Api, Basketter & Lalko 2014, Cutaneous and Ocular Toxicology Industry-funded Link to this fact
The industry / Measured in people or real products
The study's own authors note that current diagnostic patch-test concentrations for oxidized linalool allergy are more than 500 times higher than the hydroperoxide levels they actually found in consumer products.
Moderate evidence: Industry-funded interpretation; does not itself prove patch tests over-diagnose, since already-sensitized skin can react to much lower doses than the diagnostic test threshold.
Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact
The industry / Measured in people or real products
Despite thousands of positive allergy-test reactions to oxidized limonene and linalool reported worldwide, the fragrance industry's own market-testing program concluded that where people are actually getting exposed to these allergens "remains elusive" — the industry itself has not identified the real-world consumer-product source of a widely documented skin allergy.
Moderate evidence.
Caveats
This is the industry's own conclusion, from an industry-funded study; it does not mean the allergy is not real or not caused by fragrance chemicals — only that the specific consumer-product exposure route has not been chemically confirmed even by the party with the strongest incentive to find an innocuous explanation.
Source: Natsch 2019, Food and Chemical Toxicology Industry-funded Link to this fact
The industry / Review of other studies
When RIFM's own scientists switched from mainly human patch-test data (their 2017 categorization) to a full weight-of-evidence approach that also folds in animal, computer-model, and lab-dish data, the assigned allergy-potency category changed for 29% of the same 82 fragrance chemicals — moving to a weaker category for 20.5% of them and a stronger one for 8.5%.
Moderate evidence.
Caveats
Same authors and institution comparing their own two categorization schemes; independent validation of either scheme against real-world human sensitization rates is not addressed in this paper.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
The industry / Other evidence
The fragrance industry lowered its recommended limit for isoeugenol in consumer products from 0.2% to 0.02% in 1998, in response to documented high and rising rates of contact allergy to it.
Moderate evidence.
Caveats
A single documented industry guideline change; the review notes it is unknown whether this will actually reduce isoeugenol sensitization, since chemically similar substitutes can cross-react.
Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact
The industry / Government agency
In February 1992, the Business Council on Indoor Air (an indoor-air industry trade association) told HUD that the American Medical Association, American Association of Allergy and Immunology, American College of Physicians, and American College of Occupational and Environmental Medicine had all stated (December 1991) that there was "inadequate scientific evidence to establish the existence of MCS as a disorder," and asked HUD to correct guidance that recognized MCS as a handicap.
Moderate evidence.
Caveats
Reported via the trade association's own letter and white paper, not read directly from the cited medical-society statements; BCIA is an interested industry group asking a housing regulator to narrow disability protections, which does not by itself make its scientific summary wrong but is a relevant interest to disclose.
Source: BCIA letter (1992) Link to this fact
The industry / Lab study (cells or chemistry)
A 2022 skin-absorption study of linalool, funded by the fragrance industry's own safety institute (RIFM) and run by RIFM's long-term contract lab, tested only fresh linalool and did not report the test material's oxidation state or test air-oxidized linalool, the form clinical studies link to skin allergy.
Moderate evidence: Industry-funded (RIFM); the gap mirrors the same undisclosed-oxidation-state pattern documented in RIFM's separate 2003 sensitization dossier for linalool.
Source: Brain et al. 2022 (An-eX/RIFM), International Journal of Pharmaceutics Industry-funded Link to this fact
The industry / Journalism
The Skin Deep database draws on about 60 sources including IFRA and the industry's own Cosmetic Ingredient Review panel, the EU banned-fragrance list, and the SCCNFP fragrance-allergy opinions, with reference dates running to about 2009; the page does not state whether sources are refreshed.
Moderate evidence: Source list from the page's own references; the live database may use newer data.
Source: EWG Skin Deep methodology page (2026 capture) Link to this fact
The industry / Other evidence
The main safety data set the oxybenzone sunscreen maker offered against clinic reports of oxybenzone allergy is 64 of its own unpublished studies, written up by its employees and former employees; the authors argue clinic-based literature overstates risk because clinic patients already have skin disease.
Moderate evidence.
Caveats
The authors' point about clinic selection is fair, but their healthy-volunteer design cannot measure risk in the photosensitive people where oxybenzone photoallergy is reported. 'Meta-analysis' here means pooling the sponsor's studies, with no search or inclusion criteria.
Source: Agin 2008 (oxybenzone HRIPT), Photodermatology, Photoimmunology & Photomedicine Industry-funded Link to this fact
Laws and loopholes / Review of other studies
History shows removing the exposure works: as industrial turpentine use fell from 94.5% of US supply as a solvent in 1935 to 4.5% in 1975, turpentine skin allergy declined with it.
Moderate evidence: Ecological historical correlation.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
Laws and loopholes / Review of other studies
Multiple chemical sensitivity has no dedicated diagnostic code and is instead coded, when coded at all, under nonspecific ICD-10 codes for unspecified respiratory conditions from inhaled fumes/gas/chemical vapors (J68.9) or unspecified allergy/hypersensitivity/idiosyncrasy (T78.4); some countries and agencies (US EPA, US ADA, Germany, Austria) have given the condition some form of recognition, while Italy's health ministry has declined to recognize it as a rare disease due to diagnostic-nosology difficulty.
Moderate evidence.
Caveats
Regulatory-recognition landscape as of this review's 2015 search cutoff and largely focused on Italy; recognition status in individual US states, agencies or other countries may have changed since, and the review does not cite the specific EPA/ADA source documents establishing "recognition.".
Source: Rossi 2018, Journal of Occupational & Environmental Medicine Link to this fact
Laws and loopholes / Government agency
For loose food and food packed at the buyer's request, EU law makes allergen information mandatory (Art. 44(1)(a)) but lets each Member State decide how it is provided, citing evidence that most food-allergy incidents trace to non-prepacked food (recital 48).
Moderate evidence: Recital 48 is the legislator's stated premise, not a measured figure in the regulation; national rules were not reviewed.
Source: EU Reg 1169/2011 (OJ L 304) Link to this fact
Laws and loopholes / Other evidence
In 2014 the Danish EPA said disperse dyes, which can cause allergy and cancer, were not regulated by REACH or other legislation; limits came from voluntary labels (Oeko-Tex, EU Ecolabel) and company restricted-substance lists.
Moderate evidence: Agency's 2014 statement about Denmark/EU; the regulatory position may have changed, and the report notes REACH does restrict azo dyes that release 22 listed amines (30 mg/kg).
Source: Danish EPA 2014, Survey of Chemical Substances in Consumer Products No. 129 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 / 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
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
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
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
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
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
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 / 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
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
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
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 / Lab study (cells or chemistry)
For several fragrance chemicals with no allergy-triggering chemical structure in their original (parent) form — including linalool and D-limonene, two of the most widely used fragrance ingredients in the world — the fragrance industry's own computer models predict that their breakdown products (metabolites) can trigger skin allergy, even though the parent chemicals were classified as non-sensitizers overall.
Moderate evidence.
Caveats
This paper's human no-effect-level data for linalool and limonene do not specify the oxidation state of the test material used; independent clinical studies already in this evidence base's contradiction register find that once these two chemicals are exposed to air, their oxidation products are among the commonest fragrance contact allergens in European patch-test clinics.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
A standard fragrance-mix patch test misses a substantial share of true fragrance allergy: only 50-80% of people with a real fragrance allergy are picked up by it.
Moderate evidence: A review-level synthesis of other groups' clinic populations, not a general-population estimate; figures are for patch-tested eczema/dermatitis patients.
Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact
Skin allergy / Other evidence
Fine fragrances (perfume, cologne) carry more contact-allergy risk per use than the same allergen amount spread over a larger, more dilute area, because sensitization risk depends on allergen dose per unit skin area, not total allergen delivered.
Moderate evidence: General dose-response principle from cited elicitation studies, not this review's own new experiment.
Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact
Skin allergy / Other evidence
162 individual fragrance chemicals have documented reports of causing contact allergy or allergic contact dermatitis, but routine patch testing screens for only a handful of markers (fragrance mix I, fragrance mix II, balsam of Peru, HICC, and the EU's 26 labeled allergens).
Moderate evidence: A single author's own literature tally, not a systematic review with stated search criteria; the same paper's abstract rounds this down to "more than 150".
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
Skin allergy / Review of other studies
Limonene and linalool are often weak allergens when fresh, but after a container is opened they oxidize in air into far more potent allergenic hydroperoxides, which are now among the most frequent causes of new fragrance contact allergy (reaction rates of about 2.5%-9.4% for oxidized limonene and 3.9%-11.7% for oxidized linalool across several patch-test studies).
Moderate evidence.
Caveats
Pooled ranges across several studies of varying design in this secondary review; the underlying phenomenon is independently replicated elsewhere in our evidence base at a higher evidence grade.
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
Skin allergy / Other evidence
The standard fragrance patch-test screen (fragrance mix I, fragrance mix II, balsam of Peru) misses a large share of true fragrance allergy: this review's own cited figures range from about 40% to 70% missed depending on the comparison, and "approximately half" of relevant reactions to perfumes, deodorants, and shaving lotions go undetected by baseline testing.
Moderate evidence.
Caveats
Different underlying comparators (26-fragrance panel vs hydroperoxides vs own products) give different miss rates; a specific percentage should always name what it was compared against.
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
Skin allergy / Review of other studies
Propylene glycol, a solvent and humectant used in many deodorants, can make up as much as 73% of the product and acts as both a skin irritant and an allergen, which makes its allergy patch tests hard to interpret (positivity ranges 0.1%-3.8% across studies).
Moderate evidence.
Caveats
Concentration and positivity-range figures are secondary citations (to Fiume 2012 and other cited surveys, not independently verified here) relayed by a 2024 review, not this review's own data.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Skin allergy / Review of other studies
As of 2022, US dermatology guidance (American Contact Dermatitis Society) recommends patch testing for aluminum allergy with a 10% aluminum chloride hexahydrate concentration rather than the older 2%, to improve detection of this uncommon but real cause of antiperspirant-related axillary dermatitis.
Moderate evidence: A practice-guidance update relayed from a 2022 Allergen-of-the-Year designation; not itself new patch-test data.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Skin allergy / Review of other studies
Standard allergy patch testing keeps allergens on the skin under occlusion for 48 hours, with readings at about day 3 and a final reading at 72-96 hours; a reaction present at day 3 but faded by day 5 suggests irritation rather than true allergy.
Moderate evidence.
Caveats
Narrative (non-systematic) clinical review describing established, consensus patch-test methodology rather than new data; not independently re-verified against a primary methodology paper in this pass. The 'about 70 ingredients' figure in the video is not confirmed anywhere in our evidence base — our evidence base only documents a 50-allergen research panel (Diepgen 2015) and single-marker/mix testing; allergen count varies by which standard series is used (e.g., NACDG ~70-80 allergens, European baseline series ~30). A positive patch test also indicates sensitization, not necessarily current active dermatitis, and standard fragrance mixes are known to miss roughly half of true fragrance allergy (Diepgen 2015; Mann 2014, both already in our evidence base).
Source: Aristizabal-Torres 2025, JAAD Reviews Link to this fact
Skin allergy / Measured in people or real products
Only 8 of 107 surveyed deodorants/antiperspirants were free of both fragrance and fragrance-related ingredients (essential oils, biological additives), making them judged genuinely safe for patients with diagnosed fragrance allergy.
Moderate evidence: Database-derived allergen listing, not independent chemical verification; a 2008 US retail snapshot that will not reflect current formulations.
Source: Zirwas & Moennich 2008, The Journal of Clinical and Aesthetic Dermatology Link to this fact
Skin allergy / Other evidence
In 23,846 people patch tested at a London skin-allergy clinic (1984-1998), allergy to the standard fragrance mix was uncommon in children and teenagers (about 3%) but reached about 14% in women in their 60s and men in their 70s.
Moderate evidence: One clinic's referred patients, cross-sectional by age; not general-population rates, and not a follow-up of individuals.
Source: Buckley 2003, British Journal of Dermatology Link to this fact
Skin allergy / Other evidence
Women's fragrance-mix allergy rates rose earlier than men's: 7.0% of women tested in their 20s against 3.5% of men.
Moderate evidence: Clinic patients only; the authors' explanation (more use of fragranced products by young women) is a hypothesis.
Source: Buckley 2003, British Journal of Dermatology Link to this fact
Skin allergy / Other evidence
Fragrance allergy can appear very early: the youngest patients with positive fragrance-mix tests in this London series were two 2-year-old boys.
Moderate evidence: Two children among 461 aged 0-9 (13 positive, 2.7-2.9%); children who get patch tested are often those with atopic eczema.
Source: Buckley 2003, British Journal of Dermatology Link to this fact
Skin allergy / Other evidence
In a 4-year Israeli clinic series of 644 patients suspected of clothing allergy, 12.9% (83) had a confirmed allergy to a textile dye or finish resin, and disperse dyes made up about 77% of the dye reactions.
Moderate evidence: Single clinic, referral population preselected for suspicion; not a population prevalence.
Source: Lazarov 2004, JEADV Link to this fact
Information, not medical advice. See also: myths we won’t tell you.