Allergic reaction to snake venom after repeated bites of Vipera aspis

Sirs, We observed a snake biologist studying the two indigenous poisonous snakes living in Switzerland, Vipera aspis and Vipera herus [1], who had been bitten twice by a Vipera aspis within 4 years. After the first bite in 1987 he developed a severe haemorrhagic oedema spreading from the arm to the chest and finally to the groin. Initially he suffered from swelling of the tongue, dyspnoea and diffuse abdominal pain. He was treated with amoxicillin, frusemide and analgesics; no antivenom was given. After the second bite in July 1991 he presented 30 min after the event with a generalized confluent rash of the urticarial type and a typical angioedema of the face involving the mucous membranes of the mouth. The second finger of the right hand-where he had been bitten-was oedematous. Pulse rate was 85/min, blood pressure 120/70 mmHg, the lung sounds were weak and during expiration wheezing could be heard. Clinical examination revealed no further abnormalities, laboratory results were normal and no hints of a coagulation disorder could be found. Because of this clinical picture we wondered whether an allergic reaction could explain the signs after the second bite. The presence of IgE against the venom of Vipera aspis in the patient's serum, but not in controls, could be demonstrated in a dot assay. For higher sensitivity the test was performed by a chemiluminescence method with a biotinylated anti-lgE and avidine-peroxidase (V. Aubert, PhD; see Fig. 1). The skin-prick test with native venom of Vipera aspis was positive in the patient with a weal of 6 x 8 mm (venom-dilution 1: 10). No swelling and only slight erythema were seen in the three controls. Total IgE was 106 lU/ml (norm: ~220 lU/ml). Repeated bites by poisonous snakes occur more frequently than generally assumed, particularly in professional or amateur herpetologists [2,3]. Allergic reactions to repeated snake bites have been suspected in several