Venom immunotherapy (VIT) for large local reactions (LLR) to insect stings: A pilot study

Abstract

Rationale Patients with LLR to stings may have frequent reactions and fear systemic reactions(SR), but VIT is not recommended because their risk of SR is only 10%. We aim to investigate, in patients with previous LLR, the frequency of SR from sting challenge, and the efficacy of VIT in reducing LLR. Methods Consenting patients with a history of LLR and positive venom skin tests had an initial sting challenge while being monitored for SR (n=21). LLR >16 cm occurred in18 patients (86%), in whom VIT was started in 11 patients (3 HB, 6 YJ & 2 both) and 5 were untreated controls. All 16 patients had repeat sting challenge after 6-8 weeks. Results Skin tests did not cause LLR and were generally the same, or stronger than, those of patients with previous SRs. SR occurred in 1/21(5%) of patients stung. In treated patients the peak diameter of the LLR was reduced >30% in 78%, and >50% in 56%. The duration of the LLR was reduced >40% in 100% of the treated patients, and the time to reach the peak size was reduced >50% in 89% of patients. Controls had no change in LLR. Conclusions Patients with a history of LLR and positive venom skin tests have <10% risk of future systemic reaction, but often have recurrent LLR. VIT greatly reduced LLR and almost all patients requested to continue VIT. Further studies are required to determine the prevalence of LLR requiring VIT, and the efficacy of VIT.