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Background: Hymenoptera stings can cause systemic allergic reactions (SARs) that are prevented by venom immunotherapy (VIT). Sting challenge tests or field stings are used to evaluate the outcome of VIT., Objective: The aim of the study was to investigate the consequences of field stings in patients during or after completion of VIT, and to identify patients at higher risk., Methods: Patients treated with VIT between 1995 and 2018 were retrospectively evaluated. Contacted patients were invited to the clinic and a questionnaire was conducted regarding the history of field stings., Results: A total of 115 patients (F/M: 45/70, mean age: 38.5 ± 12 years) treated with VIT were included; 74/115 were contacted and asked about field stings after VIT cessation. A history of 73 field stings was reported in 38 patients, 25 of whom were treated with honeybee venom and 13 with common wasp venom. Eighteen of the reactions were SARs [8 with honeybees (1 grade-I, 6 grade-II, 1 grade-III) and 10 with common wasps (1 grade-I, 5 grade-II, 4 grade-III)]. There was no association between the severity of index reactions and field stings with either the honeybee or common wasp. The median duration of VIT was longer in patients showing no reaction than in patients with an SAR. Of the 7 patients on ACE inhibitors or beta-blockers, 1 asthmatic patient developed grade-II SAR due to field stings in the first year of VIT., Conclusions: This study confirms that VIT lasting at least 3 years is effective in preventing SARs after field stings.