A case of allergic contact dermatitis due to propolis tincture

Propolis or bee-glue, a resinous bee-hive product, is widely used in foreign countries as a medicinal remedy and in cosmetics. However, it is thought to be the cause of an increasing number of cases of allergic contact dermatitis. More than 180 constituents have been found in propolis and the major sensitizers are 3-methyl-2-butenyl caffeate and phenylethyl caffeate. We report a case of allergic contact dermatitis caused by a propolis tincture that was used in the treatment of a skin wound. Patch test results showed a positive reaction to both propolis and benzoin tinctures, but a negative reaction to fucidic acid. Because benzoic acid, cinnamic acid, esters of cinnamic acid, and vanillin are ingredients common to propolis and benzoin tinctures, these minor sensitizers are suspected as being the cause of allergic contact dermatitis in this case.