Immediate allergic and nonallergic reactions to Christmas and Easter cacti

Occupational exposure to Christmas cacti has been reported as a cause of type I allergy. Therefore, the prevalence of immediate-type mucosal and skin reactions related to cactus exposure was studied in 103 employees in a cactus nursery.

The study was based on a questionnaire followed by clinical examination, skin prick tests (SPT) with standard inhalant allergens and cacti, and a histamine-release test (HRT/Refix) using fresh cactus extracts as elicitor.

The questionnaire was answered by 84 (82%) of the nursery employees, and 63 (61%) were interviewed and skin prick tested; 58 of these were tested with HRT/Refix. Furthermore, 22 healthy controls were included and tested in vivo and in vitro. Cactus-related contact urticaria and/or rhinoconjunctivitis were reported by 37% of the cactus workers. Based on a combination of positive history, positive SPT, and positive HRT/ Refix to cactus, 8% of the cactus workers were allergic to cacti. No noncactus workers or controls were allergic to cacti by these criteria. Testing with fresh cactus material elicited positive SPT and negative HRT/Refix in 27 nursery workers and controls, of whom 12 had immediate-type skin and mucosal symptoms.

Christmas and Easter cacti seemed to be able to induce contact urticaria and rhinoconjunctivitis on both an immunologic and a nonimmunologic basis. Personal atopy was associated with positive reactions to cacti.