Clinical and entomological factors influence the outcome of sting challenge studies

The reported frequency of systemic reactions to challenge sting varies greatly. To evaluate the interaction of clinical and entomological factors that determine the outcome of a challenge sting. Patients allergic to yellow jacket were stung and monitored for systemic reaction. The frequency and severity of sting reactions were analyzed in relation to the species of insect used and patient characteristics. Objective systemic reactions occurred in 21 of 69 patients (30%) stung with Vespula maculifrons and in 8 of 71 patients (11%) with Vespula germanica ( P = .005). Systemic reactions were more frequent in patients with a severe history (9/30; 30%) than in those with a mild or moderate history (21/145; 14%; P = .04). In only 1 of 111 patients (0.9%) was the reaction to sting challenge more severe than previous reactions. The reaction rate was higher when venom skin tests were positive at