Alpha-isomethyl ionone
Alpha-isomethyl ionone is a fragrance ingredient and one of the fragrance allergens that EU cosmetics law requires to be named on the label above 0.001 % (leave-on) or 0.01 % (rinse-off).
- Used in
- Cosmetic ingredient (INCI)
- CosIng functions
- perfuming, skin conditioning
CosIng description: 3-Methyl-4-(2,6,6-trimethyl-2-cyclohexenyl)-3-buten-2-one
Contains / relevant to
Fragrance allergy: alpha-isomethyl ionone is a named EU fragrance allergen, relevant to people with a fragrance contact allergy. The IngrediLens database does not give it a separate fragrance flag, so if you react to it, add it as a custom ingredient filter in the app.
What to look for on labels
- Cosmetic ingredient lists use INCI names, in descending order of concentration down to 1 %; ingredients below 1 % can follow in any order.
- In the EU it must be named in the ingredient list when it is above 0.001 % in leave-on products or 0.01 % in rinse-off products; below that it can sit inside “parfum”.
Questions and answers
Is alpha-isomethyl ionone a fragrance allergen?
Yes. Alpha-isomethyl ionone is one of the fragrance allergens listed in Annex III of the EU Cosmetics Regulation, substances known to cause contact allergy in some people. Regulation (EU) 2023/1545 expanded that list from 26 to more than 80 substances.
Why is alpha-isomethyl ionone listed separately from parfum?
EU law requires these fragrance allergens to be named in the ingredient list when they are above 0.001 % in leave-on products or 0.01 % in rinse-off products, so people with a known allergy can find them.
Related
Sources
- EU Cosmetics Regulation (EC) No 1223/2009, Annex III (restricted substances)
- European Commission CosIng cosmetic ingredient database
- IngrediLens ingredient database (names, flags and notes shown on this page)
Label information, not medical advice. This page describes how an ingredient is named and labelled and how IngrediLens flags it; it cannot tell you whether a product is safe for you. Always read the label on the product itself and follow the advice of your doctor, allergist or dermatologist. If someone shows signs of anaphylaxis, use their adrenaline auto-injector if they have one and call emergency services.
Scan labels with IngrediLens
Point your iPhone camera at a food or cosmetic ingredient list and IngrediLens highlights the allergens and ingredients you chose to avoid, including other names like the ones on this page. Free to start, no account, and your data stays on your device.
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