Be Skeptical When You Hear, “I'm Allergic to Penicillin”

Patients often report histories of penicillin allergy, which forces clinicians to avoid most β-lactam antimicrobials and use other drugs that often are less effective, more toxic, and more expensive. Penicillin skin testing (PST) has been used to diagnose IgE-mediated penicillin allergy and has a negative predictive value approaching 99%. However, despite the test's accuracy, it is not used often in hospitalized patients.

In a single-center study, 146 patients with histories of penicillin allergy (but who never experienced anaphylaxis) underwent pin-prick tests followed by multiple intradermal injections to penicillin determinants and, if negative, oral penicillin challenges. During testing, one patient developed a positive intradermal react…