[Propolis-induced contact allergy].

Six patients with contact dermatitis to propolis are reported (3 women, 3 men; mean age 57 years). All three men had eczema on their hands and had acquired their sensitization in the course of bee keeping. The women had been sensitized by propolis contained in ointments of various kinds. Upon patch testing all six patients reacted to propolis and four also to Peruvian balsam. While ten flavonoids were test-negative, a cinnamic acid ester (1.1-dimethylallyl-3',4'-dihydroxy cinnamic acid ester) isolated both from propolis and from poplar buds was positive in two out of three patients; this may be the major allergen.