Risk assessment of Hymenoptera re-sting frequency: implications for decision-making in venom immunotherapy

Venom immunotherapy is highly efficacious in preventing anaphylactic sting reactions. However, there is an ongoing discussion regarding patient selection and whether and how to apply a cost-benefit analysis of venom immunotherapy. In order to help decision-making, we investigated the re-sting frequency of hymenoptera-venom-allergic patients to single out those at high risk.

In this retrospective study, re-sting data of 96 bee-venom-allergic patients and 95 vespid-venom-allergic patients living mainly in a rural area of Switzerland were analyzed. Hymenoptera venom allergy status was rated according to the classification system of H.L. Mueller [J Asthma Res 1966;3:331-333]. Different risk-groups were defined according to sting exposure and their median sting-free interval was calculated.

The risk factors for a wasp or bee re-sting were outdoor occupation, beekeeping and habitation close to a bee-house. Half of all vespid-venom-allergic outdoor workers were re-stung within 3.75 years compared to 7.5 years for indoor workers. Similarly, 50% of the bee-venom-allergic beekeepers or subjects with a bee-house in the vicinity suffered a bee re-sting within 5.25 years compared to 10.75 years for individuals who were not beekeepers.

The high degree of exposure of vespid-venom-allergic outdoor workers and bee-venom-allergic beekeepers and subjects living close to bee-houses underlines the high benefit of venom immunotherapy for these patients even if they suffered a non-life-threatening grade II reaction. Yet, bee-venom-allergic individuals with no proximity to bee-houses and with an indoor occupation face a very low exposure risk, which justifies epinephrine rescue treatment for these patients especially if they have suffered from grade II sting reactions.