Background: Ultra-rush induction of immunotherapy with Hymenoptera venom is a reliable and efficacious alternative to the rush induction protocol, though not widely used in European countries yet. Its safety, however, has been intensively discussed over the last few years.

The aim of this retrospective case study was to examine the rate of allergic side-effects during our four-hour ultrarush hymenoptera venom induction regimen. We evaluated risk factors for observed side-effects such as age, gender, severity of previous insect sting reactions according to the H.L. Mueller classification, concentration of venom inducing positive skin tests, level of specific IgE, serum tryptase concentration, and hymenoptera venom used for treatment.

Methods: 67 outpatients with Hymenoptera venom allergy received 80 courses of ultra-rush immunotherapy. Diagnosis and selection of patients for venom immunotherapy were carried out according to the European Academy of Allergology and Clinical Immunology. We applied a four-hour regimen, and local or systemic reactions were documented.

Results: In 78 courses (97.5%) the maintenance dose of 111.1 μg was reached within 4 hours and it was tolerated in 82.5% without any hypersensitivity reaction. Allergic side-effects were observed in only 17.5% (n=14): four severe local reactions (5%), eight grade I (10%) and two grade II (2.5%) systemic reactions. There was no significant difference in the number of systemic reactions comparing patients receiving wasp or honeybee venom extract. The number of systemic reactions was neither higher in patients with a severe prior insect sting reaction (grade III or IV) nor dependent on age, gender, skin test reaction, level of specific IgE or tryptase. Epinephrine as rescue medication was never needed. Interestingly, patients with a severe prior wasp sting reaction showed a significantly lower incidence of allergic side-effects during ultra-rush immunotheraphy with wasp venom extract as compared to grade III or IV honeybee venom allergic patients.

Conclusion: Our ultra-rush immunotherapy induction regimen shows a low incidence of systemic reactions. It proved to be safe and convenient for the patient, as it could be applied in a four-hour outpatient regimen.

Key words: Ultra-rush immunotheraphy, Hymenoptera venom allergy, wasp, honeybee, side-effects, safety.