Volatile fragrance and flavor ingredient that must be listed on products containing it because of its risk of causing a sensitized reaction at concentrations as low as 0.001%. It is an ingredient to avoid if you have sensitive skin, especially since it is almost always combined with other volatile fragrance components such as linalool and eugenol https://www.paulaschoice.com/ingredient-dictionary/ingredient-alpha-isomethyl-ionone .html?q=Alpha-Isomethyl%20Ionone&fdid=ingredients