Fixed drug eruption following metronidazole therapy and the use of topical provocation testing in diagnosis.

Fixed drug eruption is characterized by recurrent well-defined lesions appearing in the same location each time the drug responsible is taken. A number of agents have been implicated. Metronidazole, a nitroimidazole agent widely used for its antibacterial and antiprotozoal activity, has been reported only rarely as the causative agent. We describe a patient with FDE due to metronidazole in whom we were able to induce the clinical and histological features of FDE by topical provocation testing. In agreement with the published literature we commend the use of topical provocation testing as a possible first-line investigation in the diagnosis of FDE. This may avoid the need for subsequent oral provocation testing and therefore the prevention of possible adverse sequelae.