Abstract

The alpha-gal syndrome or red meat allergy is the first known IgE-mediated allergic disease caused by a carbohydrate epitope (galactose-alpha-1,3-galactose, alpha-gal). Alpha-gal is found in the meat and inner organs of different mammals, but is absent in humans as they lack the enzyme needed for formation of the epitope. The alpha-gal syndrome presents as an anaphylactic reaction, urticaria or angioedema after consumption of foods containing alpha-gal epitopes (mammal meat or inner organs, but possibly also milk and dairy products or sweets containing gelatine). The syndrome is characterized by a long interval (approximately 3-6 hours) between ingestion of the allergeen and development of allergic reaction. Different cofactors, e.g. physical activity, alcohol, and drugs, may influence the development of allergic reaction. In addition to foods, the alpha-gal syndrome may also be caused by colloids or drugs containing gelatine. In the case of parenteral or topic administration of the allergen, the allergic reaction is not delayed. In vitro tests that detect IgE against alpha-gal or mammal meat may be used to diagnose the syndrome. Skin prick tests using commercial of freshly prepared meat extracts are less sensitive compared to in vitro tests. Food challenges can be used too; however, the long latency between ingestion of the allergen and development of the reaction, as well as the variability of the reaction complicate the use of challenge tests. Although avoiding the allergen is the mainstay in the treatment of the syndrome, avoiding all mammal products is generally not necessary.