Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: 10 coumarins used in perfumery, cosmetics and ointments, have been investigated by 2 different methods to determine their sensitizing capacity. Only 1 of the compounds, 4-methyl-esculetin, which serves as a sunscreen agent, was found to be a weak sensitizer. All other coumarins were negative. It is assumed that this dihydroxycoumarin becomes a sensitizer when it is enzymically oxidized to the corresponding orthoquinone in the skin.
Animal