Lack of reproducibility of a single negative sting challenge response in the assessment of anaphylactic risk in patients with suspected yellow jacket hypersensitivity.

To investigate the reproducibility of a single negative response to sting challenge with a living insect, we rechallenged a group of 61 patients who showed no clinical response to a first sting challenge. All patients had previously had symptoms suggestive of anaphylaxis after a yellow jacket field sting. Thirteen patients (21%) had anaphylactic responses after the second sting challenge, and six of these patients had severe reactions including symptomatic hypotension requiring administration of Adrenalin. This rate was significantly lower than the response rate of the original patient group to a first sting challenge (39%). Thus although fewer positive responses were observed in patients who had had a previous negative challenge response, the number of anaphylactic reactions was considerable and included patients with potentially life-threatening symptoms. Consequently, a single sting challenge may not be used to select patients for venom immunotherapy.