Meat allergy and alpha-gal syndrome

Two decades ago, meat allergy was not well understood, patterns of overlap between reactivity to different meats were not clear and it was less commonly diagnosed. Today our understanding has grown tremendously and patients with meat allergy can be diagnosed with more accuracy. Sensitization may be acquired through the gastrointestinal tract, the airways or the skin. Thorough history taking and utilization of in-vitro and in-vivo diagnostic measures allow us to determine cross-sensitization and clinically relevant cross-reactivity with implications for patient management and reduction of risk for meat allergic individuals. Specific IgE-binding to meat extracts and to single components primarily from beef, chicken, pork, milk, egg, chickens and alpha-gal help to make specific diagnoses. Milk/beef syndrome results from specific IgE binding serum albumin (Bos d 6), cat-pork syndrome from specific IgE to cat Fel d 2 cross-binding with pork serum albumin (Sus s 1), bird-egg syndrome from specific IgE recognizing serum albumin from chicken (Gal d 5) and fish/chicken syndrome that can be based on several specific sensitizations. A distinct entity is the alpha-gal syndrome (AGS) in which patients are sensitized through tick bites and react to red meat as well as food and medications derived from red meat. Allergic reactions in AGS develop as immediate type when drugs derived from mammals are administered parentally or as delayed IgE mediated allergic reactions following oral intake. In patients with AGS, poultry, fish, meat from reptiles and chicken eggs are tolerated. Skin tests, specific IgE analysis and oral challenge tests can be used to confirm the diagnosis. Co-factors such as exercise can augment the severity of a reaction or transform a mild response into anaphylaxis. Thus, co-factors should be assessed in the medical history, may be included in oral challenge tests to elicit these reactions, and should be addressed as avoidance measures for affected patients.