Immediate allergic and nonallergic reactions to Christmas and Easter cacti

Background: Occupational exposure to Christmas cacti has been reported as a cause of type I allergy. Therefore, the prevalence of immediate-type mucos al and skin reactions related to cactus exposure was studied in 103 employe es in a cactus nursery. Methods: The study was based on a questionnaire followed by clinical examin ation, skin prick tests (SPT) with standard inhalant allergens and cacti, a nd a histamine-release test (HRT/Refix) using fresh cactus extracts as elic itor. Results: The questionnaire was answered by 84 (82%) of the nursery employee s, and 63 (61%) were interviewed and skin prick tested; 58 of these were te sted with HRT/Refix. Furthermore, 22 healthy controls were included and tes ted in vivo and in vitro. Cactus-related contact urticaria and/or rhinoconj unctivitis were reported by 37% of the cactus workers. Based on a combinati on of positive history, positive SPT, and positive HRT/ Refix to cactus, 8% of the cactus workers were allergic to cacti. No noncactus workers or cont rols were allergic to cacti by these criteria. Testing with fresh cactus ma terial elicited positive SPT and negative HRT/Refix in 27 nursery workers a nd controls, of whom 12 had immediate-type skin and mucosal symptoms. Conclusions: Christmas and Easter cacti seemed to be able to induce contact urticaria and rhinoconjunctivitis on both an immunologic and a nonimmunolo gic basis. Personal atopy was associated with positive reactions to cacti.