What it is
Alpha-isomethyl ionone belongs to the ionone family of fragrance materials and contributes a powdery, violet- and orris-like scent that is widely used to round out and soften perfume accords. In sunscreens and other skincare it appears at low levels as part of a fragrance blend or to mask the base odor of the formula. It carries no skin-care function beyond scent.
Safety & warnings
Alpha-isomethyl ionone is one of the fragrance allergens that the EU requires to be declared by name on cosmetic labels when present above set thresholds, because it can cause allergic contact dermatitis in sensitized individuals. People with known fragrance sensitivity or reactive skin may prefer fragrance-free formulas. For most users at the low levels used it is well tolerated.
Origin & sourcing
It is produced synthetically. Ionones are typically made through aldol condensation of citral with acetone followed by cyclization, with this material being a methylated ionone derivative.
Questions everyone asks
Why is alpha-isomethyl ionone in my sunscreen?
It is a fragrance ingredient added in small amounts to give the product a pleasant violet-like floral note or to mask the smell of other raw materials. It has no sun protection role.
Is alpha-isomethyl ionone a known allergen?
Yes, it is on the list of fragrance substances that must be declared on labels because it can trigger allergic contact dermatitis in some sensitized people. Those prone to fragrance reactions may prefer fragrance-free options.