Occupational type I allergy to Christmas cactus (Schlumbergera).

The study aimed to determine whether occupational contact urticaria and symptoms of mucous membranes, reported by five workers in a cactus nursery, were due to IgE-mediated allergy to Schlumbergera cacti. The five persons had positive skin prick tests to the plants as is and positive histamine-release tests, and in three of them specific IgE to the cacti could be demonstrated by Maxisorp RAST and immunoblotting. Four of the patients were atopic, and the fifth had a positive skin prick test to cat dander, indicating latent atopy. Skin prick tests with cacti were negative in most atopic volunteers, and all had negative histamine-release tests. The results suggest a true IgE-mediated allergy to the cacti, and both genetic predisposition and close contact with the plants at work seem to be important factors in the emergence of this new occupational allergy.