Don’t take our word for it. Here’s every fact on this site, with its evidence grade, its caveats, and a link to the source, so you can check us.
We start you on the strong ones: findings that have been replicated or come from one large, well-controlled study. Moderate and weak facts are here too, labeled for what they are. Use “Link to this fact” to share a single card.
Skin allergy / Other evidence
About 1 in 10 people referred to North American skin-allergy clinics and patch tested in 2021-2022 (308 of 3,040, 10.1%) reacted to hydroperoxides of linalool, the air-oxidized form of a very common scent chemical; 5.7% (173 of 3,047) reacted to oxidized limonene.
Moderate evidence.
Caveats
Referral clinic patients, not the general public; most reactions were weak (+) or doubtful, and the authors say it is unclear whether these reflect true allergy or irritation (irritant reactions 2.0% and 0.9%). Single network, one two-year cycle.
Skin allergy / Other evidence
Fragrance allergy in North America is still very common but the markers that detect it are changing: the classic fragrance mixes are falling while terpene-hydroperoxide markers hold or rise.
Moderate evidence: Interpretive; the authors do not show that total fragrance allergy is unchanged, only that markers differ.
Skin allergy / Other evidence
More than 1 in 5 patch-tested patients (640 of 3,056, 21.1%) had a clinically relevant reaction to something outside the standard 80-allergen series, most often a personal care product or cosmetic (53.8% of those reactions), so a negative standard panel does not rule out a product allergy.
Moderate evidence: Relevance judged by the treating clinician; the specific allergens were not recorded; referral population.
Skin allergy / Other evidence
Methylisothiazolinone allergy in North America appears to be falling from its 2017-2018 peak (15.3% to 11.5%), with lower rates at Canadian centers (9.9%) than US centers (13.5%) after Canada banned it in leave-on cosmetics in 2018.
Moderate evidence: Ecological comparison of clinic networks; Canada vs US difference could reflect other factors; the authors call the regulatory link a hypothesis consistent with the data.
Skin allergy / Other evidence
Nickel patch testing at 5% petrolatum picked up more allergy than 2.5% (24.9% vs 22.1% positive), at the cost of slightly more irritant reactions (0.9% vs 0.3%).
Moderate evidence: Positivity is not proof of clinical relevance; 59% of nickel reactions were past relevance only.
Skin allergy / Measured in people or real products
The authors suspected that 'some or many' of their 22 propylene glycol 'allergy' cases were really irritation, because positives at 4% or more mostly failed to reproduce on retest weeks later.
Moderate evidence: Authors' suspicion, not a measured rate; many cases predate their stricter criteria.
Source: Eiermann 1982, Journal of the American Academy of Dermatology Link to this fact
Skin allergy / Other evidence
Reports of benzalkonium chloride allergy come from nurses, doctors, dentists and veterinarians and from antiseptics, antifungal creams, toothpaste, plaster of Paris and especially eye preparations; the review itself says the eye may be an exception to its skin irritant conclusion.
Moderate evidence: Case reports are not prevalence data and often lacked repeat testing or use tests, which the authors say they should have had.
Source: Basketter et al. 2004, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Other evidence
Contact allergy to parabens is relatively rare for how widely they are used: 0.6% of patch-tested US patients in 2001-02 (down from 1.7% in 1996-98) and 0.5-1.0% in Europe, against about 9% for formaldehyde and quaternium-15 in the US.
Moderate evidence: Patch-tested patients, not the general public; secondary figures; test preparations and referral differ between regions.
Skin allergy / Other evidence
Adults with benzyl alcohol allergy were about twice as likely to have leg dermatitis as benzyl alcohol-negative adults (17.8% vs 8.6%), and hand dermatitis was the commonest site (24.0%); the authors link this to chronic dermatoses and compromised skin barriers.
Moderate evidence: Stasis-dermatitis explanation is the authors' interpretation, not tested.
Source: Zheng et al. 2026, ACDS Allergen of the Year (Cutis), Cutis Link to this fact
Skin allergy / Measured in people or real products
Among 38,723 North American patients referred for allergy patch testing (2001-2016), the 303 who ended up with a stasis dermatitis diagnosis reacted more often to fragrance mix I (16.9% vs 9.8%) and to balsam of Peru (15.6% vs 8.3%) than other patients.
Moderate evidence.
Caveats
Referral population, stasis dermatitis labeled by physician after testing with no formal criteria; adjusted odds ratios were modest (1.45 and 1.54); NACDG centers, so not independent of the other NACDG reports.
Source: Silverberg et al. 2021, Arch Dermatol Res, Archives of Dermatological Research Link to this fact
Skin allergy / Government agency
EFSA found no data on food allergy or intolerance from swallowed polysorbates, only two injection case reports (polysorbate 80, non-immunological anaphylactoid and subcutaneous hypersensitivity) and skin tests in which 2 of 1,206 eczema patients reacted and patch tests were positive in 5 of 737 (polysorbate 40) and 4 of 737 (polysorbate 80) dermatitis patients.
Moderate evidence: Case reports and clinic series; patch-test denominators are patients already seen for dermatitis; oral allergenicity untested.
Source: EFSA ANS Panel (2015), full opinion, EFSA Journal Link to this fact
Skin allergy / Other evidence
Among 5,595 people referred to North American skin-allergy clinics and patch tested in 2015-2016, 11.3% reacted to fragrance mix I, 7.0% to balsam of Peru and 5.3% to fragrance mix II, three of the commonly positive allergens in the group's 70-allergen series.
Moderate evidence.
Caveats
Referral patients, not the general public; mixes are partial markers; the series tested no oxidized limonene or linalool; one of several NACDG cycles (not independent of the 2021-2022 report, same group).
Skin allergy / Other evidence
Allergy to the preservative methylisothiazolinone kept rising in North American clinics: 13.4% of patients reacted in 2015-2016 against 10.9% in 2013-2014, making it the second most common allergen after nickel and the top-ranked by the clinic group's relevance-weighted index.
Moderate evidence: Referral patients; MI was tested at 2,000 ppm, far above cosmetic use levels; later NACDG data show a decline (MI 11.5% in 2021-2022).
Skin allergy / Other evidence
Parabens had the lowest patch-test positivity of any major preservative in North American clinics (paraben mix 0.6% in 2015-2016, down from 1.2% in 2005-2006), so 'paraben-free' is not an allergy-driven choice for most people.
Moderate evidence: Paraben allergy is not the only paraben question (endocrine evidence is separate); the allergy conclusion applies to patch-test sensitization only.
What you can do / Measured in people or real products
If you have eczema, ask for patch testing that includes oxidized linalool and limonene: they are not in every standard test series, so the allergy can be missed.
Moderate evidence: The authors say more clinical-relevance data are needed before routine screening.
What you can do / Review of other studies
If you have fragrance allergy, look for benzyl salicylate on the ingredient list (and hexyl salicylate, which cross-reacted with it in human tests); EU rules require named fragrance allergens to be declared above threshold.
Moderate evidence: Cross-reaction evidence: subjects induced with 30% hexyl salicylate reacted to 15% benzyl salicylate, in an industry report.
Source: RIFM Expert Panel / Belsito 2007, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Measured in people or real products
If you have fragrance allergy or eczema, don't rely on "fragrance free", "hypoallergenic" or "dermatologist recommended": in best-selling US moisturizers these claims often coexisted with listed skin allergens, so check the full ingredient list or a dermatologist-checked product list.
Moderate evidence: Advice follows from a label survey; not tested against reaction outcomes; two authors hold equity in a product-recommendation service.
What you can do / Measured in people or real products
If you are diagnosed with oxidized-linalool contact allergy, avoiding products listing linalool or fragrance/parfum is worth doing even at low concentrations, since repeated use at product-realistic doses reproduced dermatitis in a clinical trial, and most participants who had already stopped using linalool-containing products reported their dermatitis improved.
Moderate evidence: Self-reported improvement on avoidance (4 of 5) is not blinded or controlled; the ROAT elicitation data (the stronger evidence) show reactions down to 0.3% oxidized linalool.
Source: Andersch Björkman 2014, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
If you have known fragrance allergy, ask your pharmacist or read the full leaflet (not just the outer box) for topical medicines, and request fragrance-free formulations for wound care, NSAID gels, and antiseptics where alternatives exist; if a topical medicine causes a rash, ask for patch testing with the actual product and its individual ingredients, not just the standard fragrance mix.
Moderate evidence: Practical advice drawn from a single clinic's experience; a negative fragrance-mix patch test does not rule out fragrance allergy from a specific product.
What you can do / Measured in people or real products
People with a dermatitis distributed under clothing who suspect laundry detergent can ask a dermatologist for patch testing with a 0.1% aqueous dilution of their own detergent (low enough to avoid most irritant false positives), but a single positive reaction needs further dose-response and use-testing to separate true allergy from irritation.
Moderate evidence: Based on one study's protocol; not an independently validated clinical guideline.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
What you can do / Measured in people or real products
If you suspect a deodorant is causing your skin allergy (especially if you are male), ask that patch testing specifically include fragrance mix II and HICC, since the standard fragrance mix I marker is a weaker predictor of deodorant-driven fragrance allergy.
Moderate evidence: Advice extrapolated from a correlational clinic dataset, not from an interventional study testing whether this actually improves diagnosis.
Source: Heisterberg 2011, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
Most positive reactions (7 of 10, 70%) did not appear until after 2 weeks of twice-daily deodorant use, so a short 1-2 week trial of a new product is not a reliable way to rule out a delayed fragrance allergy.
Moderate evidence: Based on 10 reactors in a single study; the authors recommend use tests run at least 4-6 weeks for this reason.
Source: Bruze et al. 2005, Contact Dermatitis Link to this fact
What you can do / Review of other studies
If you suspect fragrance allergy, ask your dermatologist to test a dedicated fragrance series, not just the standard baseline patch-test panel, including limonene and linalool hydroperoxides and your own personal products, since the baseline markers alone miss a large share of fragrance allergy cases.
Moderate evidence: Expert-opinion clinical recommendation from a review author, not a trial comparing diagnostic strategies.
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
What you can do / Review of other studies
People who suspect a fragrance allergy should choose products specifically labeled "fragrance free" rather than "hypoallergenic" or "unscented," since the latter two terms may still permit some fragrance in the product.
Moderate evidence.
Caveats
Practice advice relayed from prior clinical literature already in this evidence base (see src-2007-benzyl-alcohol-covert-fragrance, src-2024-whiff-of-trouble-allergic-contact-dermatitis-fragrance); US labeling terms are not legally standardized.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
What you can do / Review of other studies
If a standard allergy patch-test panel is negative but a fragrance or contact allergy is still suspected, ask about extended/reflex testing with fragrance mixture II, balsam of Tolu, lichen acid mix, hydroperoxides of limonene and linalool, and (for suspected aluminum allergy) 10% aluminum chloride hexahydrate.
Moderate evidence.
Caveats
A US clinical-practice recommendation; the register records disagreement between expert groups over whether oxidized limonene/linalool preparations over-call weak reactions as true allergy.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
What you can do / Measured in people or real products
If you test positive for oxidized linalool specifically, it may be worth asking your dermatologist to test more broadly for cosmetic-related allergens (preservatives, colophony, other fragrance-mix ingredients), since concurrent allergy to several of these was common in this study's linalool-HP-positive group.
Moderate evidence: Based on patch-test association data from one Swedish clinic; not a clinical practice guideline.
Source: Sukakul 2024, Contact Dermatitis Industry-funded Link to this fact
What you can do / Review of other studies
If you have diagnosed fragrance or deodorant-ingredient allergy, ask your dermatologist about expanded patch testing (balsam of Tolu, fragrance mix 2, botanicals, lichen acid mix) if a standard fragrance screen is negative but suspicion remains, since the standard screen is estimated to miss a meaningful share of true fragrance allergy.
Moderate evidence: Practice recommendation from a narrative clinical review, not from an interventional study measuring whether expanded testing changes diagnostic outcomes.
Source: Zirwas & Moennich 2008, The Journal of Clinical and Aesthetic Dermatology Link to this fact
What you can do / Other evidence
If a rash persists in areas of clothing friction, ask a dermatologist for patch testing with textile dye and resin series; PPD and formaldehyde in the standard series missed most textile dye and resin allergy (only about 7% and 33.5% co-reacted).
Moderate evidence: Single-center observation; the recommendation is the author's.
Source: Lazarov 2004, JEADV Link to this fact
What you can do / Review of other studies
Plain petrolatum is the usual lanolin-free substitute: it cuts water loss through the skin by more than 98% with essentially no allergy risk.
Moderate evidence: Secondary citation of one review figure; glycerin and some plant oils are also suggested alternatives.
Source: Johnson 2023, Cutis Link to this fact
What you can do / Other evidence
If eczema keeps returning, ask for extended patch testing that includes the oxidized limonene and linalool hydroperoxides, and check products against the CAMP database; basic screening can miss fragrance allergy.
Moderate evidence: Practice recommendation from a consensus committee; not every clinic uses the extended series.
What you can do / Review of other studies
If you have a proven preservative allergy, check the label for the specific name and synonyms and ask your clinic for a written list: formaldehyde releasers, MCI/MI and parabens are the common preservatives, and 17-28% of creams in three studies were labeled incorrectly.
Moderate evidence: Advice follows from patch-test and label data; it does not tell which product is safe.
Information, not medical advice. See also: myths we won’t tell you.