BACKGROUND Two patients experienced itching conjunctivitis, running nose, tightness of the throat and coughing during preparation of fresh asparagus. Eating asparagus after cooking did not provoke any allergic symptoms. Both patients were atopic, sensitized additionally to pollens of grasses and trees as well as to onion. OBJECTIVE To assess the hypersensitivity reactions to fresh and heated asparagus and to investigate any crossreactivities among the allergens. METHODS Skin-prick tests were performed with commercial allergens and native asparagus and the patients were tested with Pharmacia CAP system for specific IgE antibodies against asparagus, onion, garlic, birch pollen, mugwort pollen and two recombinant birch pollen allergens, Bet v I and profilin. Inhibition of IgE antibody binding to solid phase homologous and unrelated allergens by increasing doses of liquid allergens (inhibitors) was studied. RESULTS Skin-prick tests with native green and white asparagus were strongly positive, but negative with cooked asparagus. Both patients had measurable levels of IgE antibodies against asparagus (3.0 and 6.2 kU/L respectively) and several other allergens. One patient was highly sensitive to birch and Bet v I. Both were positive to profilin, mugwort and onion. In all cases the antibody uptake could be extensively and specifically inhibited by homologous allergen. The asparagus-specific IgE antibodies of the two patients could only be inhibited by asparagus. No inhibition was obtained after heating of the asparagus extract to 100 degrees C. CONCLUSIONS The patients were specifically sensitized by asparagus. No immunological crossreactions could be observed. The measurements of IgE antibodies to other allergens were also specific, representing parallel multiple sensitivity. Profilin inhibited profilin-specific IgE binding but did not react with the asparagus-specific IgE antibodies of these patients. The asparagus allergen recognized by the specific IgE antibodies of these patients was thermolabile.