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 these subjects, the skin-prick test positivity to and presence of specific serum immunoglobulin (Ig)E for barley malt, the basic ingredient used in brewing, 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, some of them suffering from baker's asthma, were examined for both prick test sensitivity to and the occurrence of serum-specific IgE for partially purified proteins from beer. Allergen identification in beer, malt and barley was 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 beer protein fraction contained the allergen. Immunoblot analysis with sera of patients with urticaria from beer showed that IgE bound only the 10-kDa protein 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 reaction induced by a protein component of approximately 10 kDa deriving from barley. This allergen does not seem to be related to the major barley 16-kDa allergen responsible for baker's asthma. Because of the severity of the allergic manifestations to beer we recommend testing atopic patients positive to malt/barley and/or who exhibit urticarial reactions after drinking beer for their sensitivity to this beverage.