D3.185 - Clinical Characteristics of Patients with Hymenoptera Venom Allergy Treated with Venom Immunotherapy: A Retrospective Study

Hymenoptera venom allergy is one of the most common causes of anaphylaxis. Venom immunotherapy (VIT) is the only immunomodulatory treatment with proven efficacy in preventing IgE-mediated systemic reactions. In this study, we retrospectively evaluated the clinical characteristics, treatment efficacy, and adverse effects of patients undergoing VIT.

A total of 305 patients who presented with a history of systemic reactions following Hymenoptera stings were included in the study. Diagnosis was supported by skin prick tests, measurements of total IgE, venom-specific IgE, and baseline serum tryptase levels. According to sensitization profiles, VIT was initiated with Apis mellifera, Vespula vulgaris, or both venoms. Rush or cluster protocols using aqueous or depot venom extracts were applied. Adverse reactions during VIT and responses to re-stings after VIT were retrospectively reviewed from medical records and supplemented by patient interviews when necessary.

Venom immunotherapy was administered to 153 patients sensitized to Apis, 147 to Vespula, and 5 patients sensitized to both venoms. The severity of index systemic reactions was Grade I in 4.7%, Grade II in 8.7%, Grade III in 50.2%, and Grade IV in 36.5% of patients (Table 1). No association was observed between the severity of the initial reaction and the culprit insect species.

During VIT, systemic reactions occurred in 25% of patients, while large local reactions were observed in 23.9%, with a similar distribution during the build-up and maintenance phases. Systemic reactions were more frequently observed with Apis venom and were predominantly Grade I–II in severity (Table 2).

Among patients who experienced re-stings, 17.9% developed systemic reactions. In patients receiving VIT for more than three years, 87% experienced no reaction or only local reactions, whereas mild systemic reactions were observed in 12.7%. Epinephrine auto-injectors were used by 5.7% of patients, and adrenaline was administered in the emergency department in 15.5% of cases (Table 3).

This study demonstrates that venom immunotherapy is an effective and safe treatment for Hymenoptera venom allergy. Elevated baseline tryptase levels and Apis sensitization emerged as major risk factors for systemic reactions. A treatment duration of at least three years appears essential for achieving adequate tolerance to Hymenoptera stings. Furthermore, patients should be encouraged to carry and appropriately use epinephrine auto-injectors in emergency situations.