An unusual drug eruption to ampicillin.

The authors describe an unusual presentation of ampicillin allergy. A 24-year-old Chinese man noted localized pustular skin eruptions on his cheeks each time he ingested ampicillin. These eruptions would subside spontaneously within a week after stopping use of ampicillin. Drug provocation with ampicillin reproduced the same eruption in exactly the same sites. The eruptions were different clinically and histologically from fixed drug eruptions. The mechanism of such eruption is unknown.