Non-pigmenting fixed drug eruption caused by allylisopropylacetylurea.

An unusual case of a non-pigmenting fixed drug eruption caused by allylisopropylacetylurea is reported. Several hours after taking an analgesic (New Kaiteki A), a 30-year-old Japanese woman, who had experienced similar eruptions several times after taking other analgesics, developed numerous variously sized, itchy, round-to-oval erythematous eruptions on the trunk and extremities. After she discontinued taking this drug, all such eruptions resolved within 2 weeks, without leaving postinflammatory pigmentation. Patch testing with New Kaiteki A itself and one of its active ingredients, allylisopropylacetylurea, on lesional skin, but not on uninvolved skin, showed positive erythematous reactions after 2 days.