What is it?
Alpha-isomethyl ionone is a synthetic fragrance and often used in cosmetics.

How do I avoid it?
Skin contact with alpha-isomethyl ionone is required for it to cause a rash. Discontinuation of exposure to products containing alpha-isomethyl ionone should result in improvement and/or resolution of your dermatitis. By law, all products made in the U.S. for topical use have the ingredients listed either on the product package or the box that contains it, so check the labeling of your skin care products for this ingredient. If there is not enough information, ask your pharmacist or retailer, or contact the company directly. At work, request a Safety Data Sheet (SDS) to help identify potential sources of exposure.

The avoidance of fragrances such as alpha-isomethyl ionone can be difficult, since so many everyday products contain these substances. One should use only fragrance-free cosmetic and household products. “Unscented” products may contain low levels of a fragrance to cover up an undesirable odor and also should be avoided. Products labeled as “hypoallergenic” do not assure that the
product is truly free of fragrance.

Since fragrances are complex mixtures of many ingredients, an individual may tolerate one fragrance but not another. A trial-and-error method of avoiding a fragrance allergen in a product can be performed by applying the product to the forearm in the same small area twice a day for a week. If no dermatitis develops, the product may likely be used safely.

  • Skin care products/Cosmetics
    • Antiperspirants/Deodorants
    • Hair sprays, gels
    • Foot cream
    • Moisturizers
    • Shampoos
    • Shaving cream
    • Soaps/Cleansers/Scrubs
  • Floral fragrances
  • Household detergents
  • Deodorants
  • Home and car fresheners
  • Soaps
Other names for alpha-isomethyl ionone:
  • 3-methyl-4-(2,6,6-trimethylcyclohex-2-enyl)but-3-en-2-one
  • Cetone alpha
  • α-isomethylionone
Cross-reacting substances:
  • Other fragrances

How safe is it?

Hang tight. We're thinking.