Penicillin resensitization among hospitalized patients.

The purpose of this study was to determine the frequency of resensitization to penicillin after oral or intravenous treatment with beta-lactam antibiotics in hospitalized patients with histories of penicillin allergy. Seventeen adults (aged 24 to 76 years) and one child (aged 10 years) were treated intravenously and/or orally with beta-lactam antibiotics after negative skin tests were obtained with benzylpenicilloyl polylysine, potassium penicillin G, and alkaline hydrolysis products of penicillin G as minor determinant mixture. Repeat skin testing was performed 1 to 12 months after the therapy. Three patients (16%) became skin test positive after the treatment. Two patients reacted to potassium penicillin G alone, and the other patient reacted to benzylpenicilloyl polylysine and minor determinant mixture. These three patients were among the 15 patients who were treated with intravenous antibiotics. This study reveals a high percentage of skin test conversion after intravenously administered penicillin therapy and confirms the present practice of advising patients with a history of penicillin allergy who have successfully completed penicillin treatment to have a repeat skin test before future exposure to beta-lactam antibiotics.