Fixed drug eruption due to allylisopropylacetylurea.

We report a case of fixed drug eruption due to allylisopropylacetylurea. A 21-year-old female developed purplish-red round eruptions on her neck and left thigh after taking an analgesic containing isopropylantipyrine, allylisopropylacetylurea, phenacetin and anhydrous caffeine. Patch testing with the analgesic and its ingredients on the eruptive area showed positive reactions to the analgesic and allylisopropylacetylurea, while patch testing on the non-eruptive area showed negative reactions. We diagnosed her condition as a fixed drug eruption due to allylisopropylacetylurea in an analgesic.