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.
What you can do / Review of other studies
Close deodorant containers after use and replace them about a year after opening: two of the most common deodorant fragrances (limonene, linalool) are rated weak allergens fresh but oxidize in air into much stronger sensitizers.
Weak evidence.
Caveats
Klaschka relays this oxidation chemistry from prior studies (Karlberg 1994, Matura 2005, Skold 2008), already in our evidence base; she adds no new dose data of her own. Downgraded to weak 2026-09-28 (Jev audit): the action goes beyond what this paper itself tested.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
What you can do / Measured in people or real products
People patch-tested positive to isoeugenol or Fragrance Mix I should avoid isoeugenol-containing deodorants entirely rather than relying on IFRA-compliant "low" concentrations, since the current 0.02% cap sits inside the range this study showed can elicit reactions in sensitized users.
Weak evidence: Extrapolated consumer advice from a clinical elicitation study; not itself a tested intervention. Graded weak: what-you-can-do resting on one small ROAT study.
Source: Bruze et al. 2005, Contact Dermatitis Link to this fact
What you can do / Lab study (cells or chemistry)
Choosing a roll-on or stick deodorant instead of a spray from the same product line may reduce exposure to the estrogen-active fragrance ingredients this one lab's testing found concentrated in sprays.
Weak evidence.
Caveats
Rests on a single lab's testing of 25 German products; dispenser-type differences most likely reflect how much fragrance a given carrier formulation needs, not a demonstrated safety difference, and this has not been independently replicated or linked to any human exposure or health outcome.
What you can do / Measured in people or real products
Parabens turned up in the breast tissue of 7 women who said they had never used underarm deodorant or antiperspirant, so underarm products are not the only way parabens get into the breast.
Weak evidence.
Caveats
Only 7 never-users, self-reported lifetime use, older than the users, and no data on other personal care products (lotions, creams) that also contain parabens, so the real source is unknown.
Source: [[src-2012-measurement-paraben-concentrations-breast-tissue-serial-locations|Barr 2012]], Journal of Applied Toxicology Link to this fact
What you can do / Other evidence
In the industry model for one fragrance chemical (2-phenylethanol), the highest skin dose per area was under the arms (95th percentile about 5,258 micrograms per cm2, nearly all from deodorants), far above the neck (911) or lips (829).
Weak evidence: Illustrative only; authors cite dermal uptake of this chemical under 10%, so absorbed dose would be lower.
Source: Safford et al. 2015, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
What you can do / Measured in people or real products
In 21 patients whose hydroperoxide allergy was judged certainly relevant, the products blamed were mostly rinse-off products such as soap and shampoo (15 of 21), then leave-on cosmetics and creams (9 of 21), plus detergents, deodorants and perfumes.
Weak evidence.
Caveats
Small subgroup from one clinic; product type is the patient's and dermatologist's identification of products containing limonene or linalool on the label, not confirmed hydroperoxide content.
Source: Dittmar & Schuttelaar 2019, Contact Dermatitis Link to this fact
Information, not medical advice. See also: myths we won’t tell you.