Despite the large worldwide beer consumption, allergic reactions have very rarely been reported. We describe two cases of severe systemic reactions due to beer ingestion: one case of anaphylaxis requiring emergency care and one of generalized urticaria and angioedema. The two patients underwent a detailed diagnostic procedure involving skin testing, oral challenge with additives, detection of specific IgE to the components of beer, and oral challenge with beer in one patient. The results of the tests, in the particular skin tests and IgE assay, allowed us to detect barley as the specific ingredient responsible for the observed allergic reactions to beer. Therefore, such a sensitization should always be taken into account in the case of suspected reactions following beer ingestion.