Hypersensitivity to trimethoprim.

Abstract

We present two patients who experienced life-threatening immediate reactions and one patient who developed generalized urticaria following oral administration of trimethoprim (TMP) and sulfamethoxazole (SMX) combination. Skin prick tests with TMP were positive in the three patients. No patients reacted to skin prick tests with SMX. No significant levels of IgE antibodies to TMP were found by RAST in the serum of the patients. Normal subjects used as controls did not react to any of these tests. Single-blind, placebo-controlled oral challenges were positive with TMP and negative with SMX in all patients. These results suggest that the three patients developed type I hypersensitivity reactions to TMP. In our patients skin prick tests with TMP were useful in TMP hypersensitivity diagnosis.