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.
Fragrance is everywhere / Government agency
Alpha-isomethyl ionone, an allergen on the EU's 1999 labeled list, was declared on 46.6% of 88 deodorants checked in 2007 and detected in about 65% of 23 analyzed deodorants (6-2,588 ppm); it was found in 21.7% of 516 consumer products in another survey.
Weak evidence.
Caveats
Small, older market surveys cited from other authors (German/Danish samples); label-declaration frequency, not exposure; the underlying patch-test rates for this chemical are low (0-2.1%).
Skin allergy / Government agency
Alpha-isomethyl ionone ranks as an established human contact allergen in the EU opinion (category ++, 11-100 reported cases), but individual patch-test studies found positive rates of 0% to 2.1%, and the industry's own review lists four negative human induction tests.
Weak evidence: Low case counts and low prevalence; the industry review is the industry's position; the ++ rating partly reflects how often it has been tested.
Information, not medical advice. See also: myths we won’t tell you.