Prognosis of patients reacting with urticaria to insect sting. Results of an in-hospital sting challenge.

Insect sting challenge in 14 patients with urticarial reaction to last insect sting resulted in two systemic reactions (95% confidence limits 0-6 patients), a reaction rate of 14%. Skin prick test, basophil histamine release, RAST, and allergen-specific IgG, alone or in conjunction, could not indicate the patients to react systemically after sting challenge. Further, the systemic reactions were uninfluenced by type of insect and time elapsed since last insect sting. It is concluded that the reaction to future insect stings cannot be predicted by the immunological tests presently available.