D1.88 - An unusual diagnostic aid for Hymenoptera venom genuine versus cross sensitization: the field sting

BACKGROUND

Diagnosis of Hymenoptera venom (HV) allergy, a cause of potentially fatal anaphylaxis, relies on commercially available marker and cross-reactive molecular allergens to distinguish between genuine and cross-sensitization to Vespid (wasps, hornets) and Apid (mainly bees) venoms. True double sensitization is frequent and may complicate the management strategy, especially the choice of venom immunotherapy (VIT).

CASE

A 37-year old female presented in February 2026 for investigation of a possible HV allergy.  She reported edema, erythema, intense pain of the hand, wrist and forearm, and transient dizziness immediately after a honeybee sting in June 2025. She recalled being stung by a wasp when she was in her twenties. Serum IgE to bee and wasp venom extracts measured in June 2025 the day after the sting were 2.4 kUA/L and 2.2 kUA/L. Acute tryptase was not sampled. The February 2026 investigation found a significant increase in bee (47 kUA/L) but not in wasp venom sensitization (2.5 kUA/L), and confirmed genuine double sensitization (IgE to bee venom marker allergens Api m 1 and Api m 10 and to Vespid marker allergens Ves v 5 and Ves v 1 at concordant levels with the corresponding extracts). Functional confirmation was obtained from a basophil activation test (BAT), which was markedly positive for bee venom (93%) but not wasp venom (11%, unstimulated control 4%). Baseline tryptase was measured at 2.8 µg/L.

CONCLUSION

In this case, the field sting by a honeybee in a patient with genuine HV cosensitization resulted in a selective 20xincrease in bee venom IgE without affecting wasp venom IgE, confirming the lack of sensitization to cross-reactive Apid and Vespid molecular families. BAT confirmed the functional relevance of both HV, albeit at very different levels. Considering VIT, these findings collectively support initiating bee VIT without wasp VIT.