Red meat allergy in Sweden: association with tick sensitization and B-negative blood groups.

To the Editor: Over the past few years, allergy to mammalian meat has been identified as a new syndrome of food allergy presenting as symptoms of delayed severe allergic reactions after consumption of red meat (beef, lamb, or pork). These allergic reactions are directed against the carbohydrate galactose-a-1,3-galactose (a-Gal). In the initial studies on red meat allergy, Commins et al observed that the geographic distribution of IgE antibodies to a-Gal in the United States overlapped the region where the tick Amblyomma americanum is common, suggesting that tick bites might be relevant to these reactions. Since then, several reports have confirmed a relationship between tick bites and red meat allergy. We have recently identified a-Gal in the gastrointestinal tract of the European tick Ixodes ricinus, which provides further evidence of the tick as an initiator of red meat allergy. In this study we have identified 39 patients with a history of allergic reactions after consumption of mammalian meat and IgE against a-Gal (ImmunoCAP; Thermo Fisher Scientific, Uppsala, Sweden; median, 20 kUA/L; range, 1.3-130 kUA/L; Table I). With the exception of 2 patients, they all described delayed symptoms in which urticaria was dominant, but as many as 45% had experienced anaphylaxis (Table I). All patients had IgE against