Seasonal occupational asthma in an agricultural products merchant--a case report

A 52-year-old agricultural products merchant reported mild occupational asthma and rhinitis throughout the year, with severe asthma from February to May. He had been exposed to various substances, particularly grain, insecticides, fungicides, and fertilizers over 35 years. We identified a castor-bean-containing fertilizer as the cause of the disease by skin prick test and bronchial provocation test. Specific IgE against castor bean was detected by enzyme allergosorbent test, and proteins with mol. mass of less than 14.4 kDa and masses of 15.5, 29.5, and 30.5 kDa were identified as allergens by Western blot analysis. The seasonal character of symptoms could be explained by a more frequent use of the fertilizer during spring. Six months after avoidance of the allergen, the patient reported chronic bronchitis without asthma. Occupational allergy to castor bean should be considered in subjects with seasonal asthma and exposure to "natural" fertilizers.