Urticaria from beer: an immediate hypersensitivity reaction due to a 10-kDa protein derived from barley

Background Urticaria from beer has been reported in atopic patients. In the se subjects, the skin-prick test positivity to and presence of specific ser um immunoglobulin (Ig)E for barley malt, the basic ingredient used in brewi ng, suggested a type I hypersensitivity to barley component(s). Objective To identify the beer allergen(s) and to investigate the presence of related proteins in barley. Methods Three patients with urticaria from beer and other atopic people, so me of them suffering from baker's asthma, were examined for both prick test sensitivity to and the occurrence of serum-specific IgE for partially puri fied proteins from beer. Allergen identification in beer, malt and barley w as performed by immunoblotting. Results Skin-prick tests and detection of specific IgE by both solid-phase (RAST) and liquid-phase (AlaSTAT) assays demonstrated that the 5-20-kDa bee r protein fraction contained the allergen. Immunoblot analysis with sera of patients with urticaria from beer showed that IgE bound only the 10-kDa pr otein band in beer and malt, whereas a main 16-kDa protein was revealed in barley in addition to a very faint 10-kDa band. With the serum of a patient suffering from baker's asthma no IgE binding bands were observed in beer, whereas specific IgE binding to several proteins, including a major 16-kDa component, were detected for both malt and barley. Conclusions Urticaria from beer is an IgE-mediated hypersensitivity reactio n induced by a protein component of approximately 10 kDa deriving from barl ey. This allergen does not seem to be related to the major barley 16-kDa al lergen responsible for baker's asthma. Because of the severity of the aller gic manifestations to beer we recommend testing atopic patients positive to malt/barley and/or who exhibit urticarial reactions after drinking beer fo r their sensitivity to this beverage.