Are anaphylactic reactions to snake bites immunoglobulin E-mediated?

BACKGROUND Bites by poisonous European snakes of the genus Vipera lead to local tissue damage and systemic symptoms such as generalized oedema, hypotension, gastrointestinal symptoms, haemolysis and renal dysfunction. Not rarely anaphylactic symptoms like urticaria, localized angioedema and asthma are observed. OBJECTIVE To look for snake venom-specific immunoglobulin (Ig) E antibodies in patients with a history of bites by European vipers and for cross-reactions with Hymenoptera venoms, that have a similar composition. METHOD Ten patients with a history of bites by Vipera aspis or Vipera berus were investigated. Three patients had been bitten only once, and two of these had developed only local reactions. Four reported previous allergic reactions to Hymenoptera stings. All patients, 10 Hymenoptera venom-allergic and five nonallergic individuals who served as controls underwent i.c. skin test endpoint titration with snake (V. aspis, V. berus) and Hymenoptera venoms (honey bee, Vespula spp.) and were investigated for specific serum IgE antibodies to the same venoms. RESULTS Seven of the eight patients with systemic snake bite reactions had both positive skin tests and serum IgE antibodies to snake venoms, while these tests were negative in the two patients with only local reactions to snake bites and all controls. Seven of the eight patients with systemic snake bite reaction also had positive skin tests and specific IgE with one or both Hymenoptera venoms. By RAST-inhibition with sera of four patients with high IgE to both Vipera and Hymenoptera venoms, partial cross-reactivity could be demonstrated in one. CONCLUSIONS Anaphylactic reactions following snake bites may be IgE-mediated, especially in patients with repeated bites.