What it is
Coumarin is a naturally occurring aromatic lactone found in plants such as tonka beans, sweet clover, and woodruff, and it is also produced synthetically for cosmetic use. In sunscreens and other personal care products it functions as a fragrance and scent-masking agent, providing a sweet, warm, hay-like note. It is one of the fragrance materials specifically tracked by cosmetic regulators because of its allergen status.
Safety & warnings
Coumarin is a recognized fragrance allergen and is among the fragrance substances that must be declared on labels in some markets when present above set thresholds. It can cause allergic contact dermatitis in sensitized individuals. People with known fragrance allergies should be cautious, and fragrance-free alternatives may be preferable for very sensitive skin.
Origin & sourcing
Coumarin occurs naturally in several plants but the material used in cosmetics is commonly produced synthetically; both nature-identical and natural sources exist.
History
Coumarin was first isolated in the 19th century from the tonka bean and became one of the early materials used in modern perfumery.
Questions everyone asks
Why is coumarin in my sunscreen?
It is used as a fragrance ingredient, adding a sweet, hay-like scent and helping mask the base odor of other ingredients.
Is coumarin an allergen?
Yes, it is a recognized fragrance allergen that must be declared on labels in some markets and can cause contact dermatitis in sensitized people.