Side-effects of insect venom immunotherapy:: results from an EAACI multicenter study

Background: The effect of venom immunotherapy (VIT) is well documented, but fear of systemic side-effects (SE) may prevent its use. The study aimed to analyze the character and frequency of SE and risk factors. Methods: In a prospective study, 19 European centers included patients starting on VIT for systemic reactions to insect stings. Various dose regimens were applied. Results: Data from 840 patients with a total of 26 601 injections were obtained. Seventy-one percent were treated with Vespula-venom extract and 27% with honeybee-venom extract. Twenty percent of patients had SE corresponding to 1.9% of injections during dose increase and 0.5% during the maintenance phase. The vast majority of the 280 reactions were mild: only one-third required medical treatment. Injected or inhaled adrenaline was applied in six patients, of whom only one had a drop in blood pressure and collapse. Female sex, bee-venom extract, and rapid dose increase, but not severity of insect sting reactions, increased the risk of SE. The severity of SE was less in males but was not related to age, treatment phase, species of insect, or severity of insect sting reactions. Conclusions: The frequency of SE was low, and the majority of these could be managed without treatment. Risk was increased in females, in bee-venom-treated patients, and in those with rapid dose increase.