Fixed drug eruption: an immunohistochemical investigation of the acute and healing phase.

Five patients were each challenged orally with a drug which had previously induced a fixed drug eruption. A positive reaction occurred in all the patients. Punch biopsies were taken 6-12 h, 24 h and 3 weeks after challenge. The specimens were tested with different mouse anti-human monoclonal antibodies to identify T lymphocytes and phenotypic subsets, natural killer cells, B lymphocytes, OKT-6 and HLA-DR-positive cells. T suppressor/cytotoxic cells seemed to play a major role in initiating the flare-up reaction and preserving the cutaneous memory function of the fixed drug eruption.