Topical provocation in 31 cases of fixed drug eruption: change of causative drugs in 10 years.

The pathomechanism of fixed drug eruption remains to be clarified, but patch testing has been used to determine the causative drug. 31 patients with fixed drug eruption were investigated to evaluate the diagnostic value of patch testing and to compare the causative drugs over the 10 years between the late 1980s and the late 1990s. 22 of them were given an oral provocation test to confirm the results of patch testing. A reaction showing definite infiltration, which occurred in 13 of 22 patients, reliably indicated the causative drug. In contrast, a patch test reaction without definite infiltration was not always correlated with systemic provocation. All except 1 patient found out their causative drug. The most frequent causative drug was sulfamethoxazole-trimethoprim in the late 1980s, but it had become chlormezanone 10 years later.