Venom immunotherapy: adverse reactions and treatment failure

Side effects of venom immunotherapy and lack of efficacy represent significant problems in the treatment of patients allergic to Hymenoptera venom. Among these side effects systemic anaphylactic reactions and large local reactions are the most important. This review aims to discuss new insights in frequency, pathogenesis and handling of these common side effects and of treatment failure during venom immunotherapy.

Several studies showed that severe side effects due to venom immunotherapy are rare. Recently published studies focus on ultrarush protocols and report good tolerance of an ultrarush venom immunotherapy in which the maintenance dose was reached within several hours or 2 days, respectively. Compared to the use of aqueous extracts (administered according to a rush protocol), frequency of local and also systemic side effects was lower when depot extracts and schedules with a slow conventional dose increase were applied. Concomitant treatment with H1-antihistamines was found to reduce local and mild systemic adverse reactions during venom immunotherapy. Up to 25% of patients are not protected when re-stung while on venom immunotherapy with the usual maintenance dose of 100 microg of venom every 4-8 weeks. These patients can achieve full protection by increasing the maintenance dose.

Conventional dose increase using depot extracts is better tolerated than if aqueous extracts are being administered. Concomitant treatment with H1-antihistamines may be helpful. Increasing the venom dose to 200 microg or even more may be therapeutically effective in patients not protected by a lower maintenance dose. To compare tolerance of different treatment protocols prospective comparative studies are required.