Immediate reactions to patch tests with balsam of Peru.

Closed patch tests with balsam of Peru gave rise to nine immediate reactions among 121 patients with different dermatoses and to 10 reactions among 57 patients with chronic urticaria. Among compounds of balsam of Peru, cinnamic aldehyde, cinnamic acid benzoic acid and benzaldehyde also gave the same reactions. The reactions could not passively be transferred with serum from patients. They were abolished by antihistamine given before testing, and by pretreatment with compound 48/80. Balsam of Peru and cinnamic aldehyde did not provoke new symptoms when given orally to patients.