Allergy to Birch Pollen and Apple, and Gross‐Reactivity of the Allergens Studied with the RAST

Abstract
Apple‐pulp allergens arc unstable, but fresh material can be used for skin testing. In this study stable allergens, probably of a protein nature, were extracted from apple seed and used in radioallergosorbent tests (RAST). Apple‐seed allergens were shown by RAST inhibition to cross‐react with birch pollen allergen(s). Cross‐reactivity may explain the frequent co‐occurrence of birch pollen and apple allergy. Approximately 50% of patients in a group with immediate hypersensitivity to birch pollen were also sensitive to apple as judged by a history of symptoms, skin tests with apple‐pulp and apple‐seed preparations, and apple‐seed RAST.