Allergic responses to pollen of ornamental plants: High incidence in the general atopic population and especially among flower growers

Background: The incidence of allergy to pollen of ornamental plants has not been deeply investigated, and its extent has remained obscure. Most of such studies have concentrated only on pollen of ornamental plants from the Asteraceae family (Compositae). In this study an attempt was made to clarify whether various other ornamental plants may also cause skin responses and allergic symptoms among allergic urban dwellers and among rural flower growers. Methods: Two hundred ninety-two patients were referred for allergic evaluation by their primary physicians; 75 flower growers and 44 university students were evaluated. For all participants, a detailed health record was obtained, and skin prick tests (SPTs) were performed. Extracts for SPTs included commercial common airborne allergens and autochthonous pollen extracts of 11 species of plants belonging to the Asteraceae, Ranunculaceae, Liliaceae, Scrophulariaceae, and Genetianaceae families. Results: Fifty-one of the 292 patients (17%) referred for allergic evaluation had positive SPT responses to pollen of various ornamental plants. A similar incidence was found among the students (23%). However, the incidence among flower growers was significantly higher, reaching 52%. Higher incidence (83%) of positive SPT responses to ornamental plants was found among flower growers also sensitive to the common allergens. All the tested plants, not only those belonging to the Asteraceae family, provoked positive SPT responses in all 3 groups of participants. None of the participants from the general population or the group of students reported exacerbation of allergic symptoms on exposure to the tested plants. In contrast, almost half of the flower growers (45%) described nasal, ocular, or respiratory symptoms associated with occupational exposure to the tested plants. Some 15% of the growers were eventually compelled to change their profession. Conclusions: The incidence of positive SPT responses to ornamental plants was 17% to 23% among the general public but 52% among flower growers. Thus the effects of ornamental plant pollen on atopic patients should be seriously contemplated.