Risk of anaphylaxis in patients with large local reactions to hymenoptera stings: a retrospective and prospective study.

Background: In the few studies available, the risk of developing systemic reactions (SR) to hymenoptera stings in patients with previous large local reactions (LLRs) to stings ranges from 0 to 7 %. We evaluated both retrospectively and prospectively the risk of SRs in patients with LLRs to stings.

Methods: An overall number of 477 patients, 396 with an SR as the first manifestation of allergy and 81 with a history of only LLRs after hymenoptera stings, were included in the study. All patients had clinical history and allergy testing (skin tests and/or specific IgE) indicative of allergy to venom of only one kind of Hymenoptera. Of the 81 patient with LLRs, 53 were followed-up for 3 years by annual control visits, while the 396 patients with SR were evaluated retrospectively.

Results: Among the 396 patients with an SR, only 17 (4.2 %) had had a previous LLR as debut of allergy, after an history of normal local reactions to Hymenoptera stings. All the 81 patients with a history of only LLRs had previously had at least two LLRs, with an overall number of 238 stings and no SR. Among the 53 patients who were prospectively evaluated we found that 31 of them (58.3 %) were restung by the same type of insect, with an overall number of 59 stings, presenting only LLRs and no SR.

Conclusions: Our findings confirm that patients with repeated LLRs to stings had no risk of SR, while a single LLR does not exclude such risk. This has to be considered in the management of patients with LLRs.