Wheat threshing dust--a "new allergen" in April-May nasobronchial allergy.

OBJECTIVE To identify the allergen(s) responsible for mid April-mid May nasobronchial allergy seen in North India. DESIGN Case control study. SETTING Children living in and around Chandigarh (urban, rural). SUBJECTS 39 children suffering from wheat harvest period (mid April-mid May) respiratory allergy along with randomly selected controls. METHODS Aerobiological surveys were done from March to June for identification of prevailing allergens for performing allergy tests. Patients were subjected to skin tests (ST), nasal provocation tests (NPT) and bronchial provocation tests (BPT) with extracts prepared from identified pollens and fungal spores. Specific IgE (SIgE) was assayed by ELISA and comparison between pre-season, season and post-season values made. RESULTS 81% patients had ST positive to antigen of wheat threshing dust (WTD), 30% to fungal antigens, 14% to wheat dust antigens and none to the wheat plant (WP) antigens. Nasal provocation test and bronchial provocation tests were also positive to WTD in 80% and 66% patients, respectively. WTD SIgE was demonstrated in 77% of ST positive patients. CONCLUSIONS These in vivo and in vitro tests confirm wheat threshing dust as a major causative inhalant allergen for the April-May nasobronchial allergy; in addition, fungal allergens also play a role in 1/3rd of these patients.