IgE antibodies in tick bite-induced anaphylaxis

The western black-legged tick, Ixodes pacificus , parasitizes reptiles, birds, and mammals throughout western North America. In California, it is the primary vector of Borrelia burgdorferi , the spirochete causing Lyme disease, and may also carry Francisella tularensis and a rickettsia of the spotted-fever group. Toxic local reactions are common, but systemic IgE-mediated reactions have never been documented. With the exception of the Australian paralysis tick, I. holocyclus , allergic reactions to tick bites have not been reported. We recently described a patient who had recurrent anaphylaxis after bites with I. pacificus . The study in this article revealed that his serum contained IgG and IgE antibodies to tick extract and that his basophils released histamine on challenge with the extract.