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 / 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
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
Deodorants that fragrance-allergic patients blamed for a rash reproduced that rash on controlled retesting 60% of the time (12 of 20 products), and the deodorants that caused a reaction contained fragrance-mix allergens at 1.3 to 8.6 times higher concentration, on average, than the ones that did not.
Moderate evidence.
Caveats
Small single-study cohort (14 patients, 20 patient-supplied deodorants), independently funded (EU/Danish/Swedish public grants, no industry money); no matched non-allergic control group was tested against the same implicated products, so an irritant (rather than allergic) contribution cannot be fully excluded for any single case.
Source: Johansen et al. 1998, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
How much fragrance-mix allergen a deodorant contained mattered more than how many different allergens it contained: deodorants that caused a reaction and those that did not had a similar number of fragrance-mix constituents present, but the reacting ones had higher concentrations of each.
Moderate evidence: Based on GC/GC-MS analysis of only 19 deodorants (13 use-test-positive/doubtful vs. 6 negative); small group sizes for a concentration comparison.
Source: Johansen et al. 1998, Contact Dermatitis Link to this fact
Skin allergy / Other evidence
Of 226 chemicals identified in 71 deodorants, 84 (37%) carried at least one chemical-structure 'alert' for skin-protein reactivity, and 70 of those were aldehydes, ketones, or alpha,beta-unsaturated aldehydes/ketones/esters – the reactive chemical classes already established as the dominant fragrance-allergen chemotype.
Moderate evidence.
Caveats
A structural alert is a hazard flag based on molecular structure only; the paper explicitly states it gives no information on potency (strong/moderate/weak) and is not a substitute for patch testing or animal studies.
Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact
Skin allergy / Other evidence
Citral, a fragrance chemical already established as a human skin sensitizer, was detected by GC-MS in 26 of 71 European deodorants tested in 1998 (15 of 22 vapo-sprays, 8 of 22 aerosol sprays, 3 of 27 roll-ons).
Moderate evidence: Presence only, not concentration; a single 1998 market snapshot from 5 European countries.
Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
In a 1996 chemical analysis of 73 European deodorants, the seven allergens used in the standard fragrance-mix patch test were very unevenly present: geraniol was found in 76% of products and eugenol in 57%, but cinnamic aldehyde in only 17% and isoeugenol in 29%.
Moderate evidence.
Caveats
Single study, one product category, purchased 1996 in 5 European countries; not replicated for deodorants specifically, though the pattern matches the same lab's later household-product survey (Rastogi 2001).
Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
The two rarest fragrance-mix allergens in this 1996 deodorant survey, cinnamic aldehyde (max 424 ppm) and isoeugenol (max 458 ppm), reached concentrations the study authors judged capable of triggering a reaction in people already sensitized to them, based on published human patch-test and use-test thresholds.
Moderate evidence.
Caveats
The judgment applies only to already-sensitized individuals and only to the single highest-concentration product found for each substance; median concentrations across the sample were more than 10x lower than the level of concern, and the authors state no conclusion can be drawn for the other fragrance-mix constituents because no-effect thresholds have not been studied.
Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
In a controlled study, deodorants containing hydroxycitronellal at 0.032% to 0.32% triggered allergic armpit rashes within a few weeks in all 7 people already allergic to the chemical, while an identical unscented deodorant on the other armpit, and the same deodorants used by 7 non-allergic people, caused no reactions (P<0.001).
Moderate evidence.
Caveats
Single-center study (Malmö only), unlike the 5-center Bruze 2003 cinnamic-aldehyde companion study graded strong; small cohort (7 test + 7 control patients), though statistically significant with a concurrent negative control group and blinded, randomized contralateral-axilla design.
Source: Svedman et al. 2003, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC/Lyral) was labeled on 13.5% of 632 deodorants in this 2015-16 Danish sample, significantly lower than the 33.0% found in an earlier 2007 Danish deodorant survey of 88 products (chi-square p<0.0001).
Moderate evidence.
Caveats
Different sampling methods and sample sizes between the two surveys (app-based self-selection vs. market survey); the comparison is suggestive of declining HICC use ahead of the EU ban, not a controlled before/after study.
Source: Bennike 2017/2018 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
Allergic contact dermatitis from textile dyes in clothing characteristically affects the borders/rim of the armpit while sparing the central vault, the opposite pattern from deodorant- or antiperspirant-caused dermatitis, which typically affects the vault where the product is applied.
Moderate evidence: Distribution pattern is a clinical observation relayed from case reports and small case series (Ryberg, Seidenari), not a controlled comparison.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
Skin allergy / Review of other studies
Contact dermatitis from deodorants and antiperspirants is overwhelmingly caused by fragrance ingredients (isoeugenol, cinnamic aldehyde, hydroxycitronellal, lyral, oak moss, ylang-ylang oil), not by the antiseptic or antiperspirant active ingredients.
Moderate evidence: Synthesis judgment by a single reviewer across multiple studies, not a head-to-head comparison of allergen rates.
Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact
Skin allergy / Other evidence
In a 4-year German patch-test study of 1,468 patients tested with their own deodorants and perfumes, 129 had positive reactions to a specific product, and 58 of them (45%) were missed by the standard fragrance-mix, balsam-of-Peru, and lyral patch tests.
Moderate evidence.
Caveats
Numbers relayed secondhand via this review, citing Uter et al.; the primary IVDK dataset is not yet in our evidence base, and the specific allergens responsible for the 58 missed reactions are not given.
Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact
Skin allergy / Measured in people or real products
In a 2008 survey of 107 deodorants and antiperspirants stocked at US Walgreens pharmacies, 97/107 (90%) contained fragrance and 51/107 (47%) contained propylene glycol, far ahead of essential oils/biological additives (11/107, 10%), parabens (2/107, 2%), vitamin E (2/107, 2%), and lanolin (1/107, 1%).
Moderate evidence.
Caveats
Allergen presence came from a pre-existing NACDG-screening-panel database built from product labeling, not from the authors' own chemical analysis of the products; single US retailer, one time point (~2008).
Source: Zirwas & Moennich 2008, The Journal of Clinical and Aesthetic Dermatology 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 / Measured in people or real products
In a clinical provocation study the authors relay secondhand, 20 deodorants applied to the axilla and forearm of 14 fragrance-sensitive patients produced a positive reaction in 60% of the deodorants tested, tracking the concentration of the allergen in the product rather than simply its presence.
Moderate evidence.
Caveats
Secondhand relay of Johansen et al. 1998's primary data; verified accurate against the primary (12/20 = 60%), now independently ingested as src-1998-deodorants-clinical-provocation-fragrance-sensitive.
Source: Zirwas & Moennich 2008, The Journal of Clinical and Aesthetic Dermatology Link to this fact
Information, not medical advice. See also: myths we won’t tell you.