The sensitizing capacity of coumarins (III).

9 coumarins used as chemical reagents, laser dyes, in perfumery, cosmetics or occurring naturally, were investigated experimentally in guinea pigs to determine their contact sensitizing capacity. 5,7-dihydroxycoumarin, limettin and 5,7-dihydroxy-4-methylcoumarin were found to be moderate sensitizers, while scoparone, isoscopoletin and 4-hydroxycoumarin were weak. The 3 laser dyes were completely negative. The results indicate that substitution in the 6 and 7 or 5 and 7 positions with 2 hydroxy groups supports allergenic capability, while other substituents (e.g., methoxy groups) in the same positions, or an additional (third) substituent, diminish activity.