Isolation and characterization of barley lipid transfer protein and protein Z as beer allergens.

Beer has recently been implicated as the causative agent of contact urticaria and severe IgE-mediated anaphylaxis. However, no allergen from beer has as yet been isolated and characterized. Two major components of 45 kd and 9 kd were detected in crude protein preparations from beer. Both components were purified; they were identified as barley protein Z(4) (45 kd) and lipid transfer protein 1 (LTP1; 9 kd). Protein Z(4) was recognized by the 4 individual sera tested but provoked weak positive responses to skin testing in 2 of 4 beer-allergic patients. Purified LTP1 showed reactivity with 3 of 4 individual sera and induced strong positive skin prick responses in all 4 patients tested. Barley LTP1 and protein Z(4) have been identified as the main beer allergens.