A 28-year-old woman with a previous atopic history had been complaining of itching and burning erythematous plaques or blister eruptions on her face and neck for the last 2 years. These lesions became red-brown and then disappeared in 1-2 weeks. However, the site of two of them had remained heavily pigmented after resolution. Sometimes, vesicular lesions affected the oral mucosa causing a burning sensation. She had noticed that these eruptions reappeared in the same location and related to menstruation (when she used to take naproxen sodium because of dysmenorrhea). Furthermore, pigmented sites became red-brown, elevated and itchy. These findings suggested a fixed drug eruption (FDE) due to naproxen, a sporadic clinical event previously reported only once. Patch tests were performed on the back (normal skin) with a series of NSAIDs, and with naproxen both on the back and on previous FDE sites. The test were negative on the back, and on previous FDE sites the skin got dark. The value of this result as a diagnostic tool was unclear so we performed an oral challenge test with naproxen which proved the diagnosis definitely.