Late summer and fall (March-May) pollen allergy and respiratory disease inNorthern New South Wales, Australia

Background: Many people in the subtropical Northern Rivers area of New Sout h Wales, Australia, blame the pollen of Tibouchina tree, which flowers at t he same time as ragweed, Bahia grass and Bermuda grass, for hayfever and as thma exacerbations during fall between March and May. Objectives: To determine whether Tibouchina pollen is allergenic. To determ ine whether airborne ragweed pollen is present in this region for sufficien t length of time and concentration to cause fall respiratory symptoms, and to determine if Bahia grass and Bermuda grass are associated with fall resp iratory symptoms. Methods: Pollen and Alternaria spores were monitored using a Burkard 7-day spore trap. Two hundred and six volunteers in the Northern Rivers area fill ed in questionnaires before skin prick tests (SPT) were performed with a pa nel of skin testing extracts. Results: One hundred fifty-three (74.3%) subjects were atopic and reacted t o one or more aeroallergens. Seventy were SPT positive to ragweed, OR 3.36 (CI 1.03 to 12.15) and 11 to Tibouchina (OR incalculable). Fifty of the 70 ragweed-positive subjects had fall hayfever or exacerbations of hayfever an d/or asthma, OR 23.4 (CI 8.90 to 64.00). Eleven subjects were SPT positive to Tibouchina extract. There was a statistical association between Bermuda grass and hayfever, but not asthma OR 13.44 (CI 1.85 to 27.04). Conclusions: Ragweed pollen was present for a sufficient length of time and concentration to sensitize and provoke fall hayfever and asthma exacerbati ons. Tibouchina pollen is an aeroallergen causing mild-to-moderate allergic symptoms in a few people. There is an association between Bahia grass and asthma in children, and between Bermuda grass and allergic rhinitis in adul ts.