Delayed anaphylaxis to red meat masquerading as idiopathic anaphylaxis.

Anaphylaxis is traditionally recognized as a rapidly developing combination of symptoms that often includes hives and hypotension or respiratory symptoms. Furthermore, when a specific cause is identified, exposure to this cause is usually noted to have occurred within minutes to 2 hours before the onset of symptoms. This case is of a 79-year-old woman who developed a severe episode of anaphylaxis 3 hours after eating pork. Before 2012, she had not experienced any symptoms after ingestion of meat products. Delayed anaphylaxis to mammalian meat has many contrasting features to immediate food-induced anaphylaxis. The relevant IgE antibody is specific for the oligosaccharide galactose-alpha-1,3-galactose, a blood group substance of nonprimate mammals. There is evidence from Australia, Sweden, and the United States that the primary cause of this IgE antibody response is tick bites. These bites characteristically itch for 10 days or more. Diagnosis can be made by the presence of specific IgE to beef, pork, lamb, and milk, and the lack of IgE to chicken, turkey, and fish. Skin prick tests (but not intradermal tests) generally are negative. Management of these cases, now common across the southeastern United States, consists of education combined with avoidance of both ingestion of red meat and further tick bites.