Fixed drug eruption.

We presented 21 patients with fixed drug eruptions. All of them had positive provocation tests, showing the usefulness of this test for diagnosis. The lesions appeared on the skin or mucous membranes within 20 min. to 10 hours, after an oral provocation test with a sub-therapeutic dose. In those cases where we performed the basophil degranulation test, they were all negative. The drug more frequently implicated was cotrimoxazole (71%). In one patient the eruption was produced by oral neomycin.