Occupational asthma caused by exposure to asparagus: detection of allergens by immunoblotting

Background Vegetables of the Liliaceae family, such as garlic or onion, hav e been reported to cause occupational asthma. However, there are few data o n adverse reactions to asparagus. We evaluated the role of asparagus as a c ause of asthma in a patient with respiratory symptoms occurring at work (ho rticulture) and studied relevant allergens. Methods A 28-year-old man complained of rhinoconjunctivitis and asthma when harvesting asparagus at work. Eating cooked asparagus did not provoke symp toms. A positive skin test reaction was observed with raw asparagus, Altern aria alternata, and grass-pollen extracts. The methacholine test demonstrat ed mild bronchial hyperresponsiveness. The patient had an immediate asthmat ic response after challenge with raw asparagus extract. Bronchial provocati on tests with boiled asparagus, A. alternata, and control extracts were neg ative. Two unexposed subjects with seasonal allergic asthma did not react t o the raw asparagus extract. Results The double-blind, placebo-controlled food challenge with raw aspara gus was negative. Serum asparagus-specific IgE was 13.9 kU(A)/l. By SDS-PAG E immunoblot, at least six IgE-binding components, ranging from 22 to 73 kD a, were detected only in raw asparagus. Conclusions We report a case of occupational asthma caused by asparagus inh alation, confirmed by specific bronchoprovocation. Immunoblot analysis show ed that asparagus allergens are very labile and quite sensitive to heat den aturation.