Extraction and properties of apple allergens.

It is shown that apple allergens are probably proteins and that they can be extracted in an active form only if reactions with phenolic compounds present in apple are inhibited. This is accomplished by incorporating chelators and solid polyvinylpolypyrrolidone in the extraction medium. Phenol, commonly used as a preservative, should not be added. With the RAST, serum-IgE antibodies capable of reacting with apple allergens were detected in 90% of patients with clinical apple allergy, in 44% of patients with clinical birch-pollen allergy and in 5-10% of patients with other atopic allergies. RAST inhibition indicated that apple and birch-pollen allergens cross-react.