Penicillin allergy that persisted after 66 years: case report.

The most common documented allergy is due to penicillin use, and penicillin allergy is often diagnosed early in childhood. However, fewer than 1% of the approximately 10% of the population with reported penicillin allergy have a true allergy. Antimicrobial stewardship programmes have employed pharmacist-led protocols to rechallenge patients with a documented history of penicillin allergy. There are published data to suggest that patients with a history of penicillin allergy can be successfully rechallenged and desensitised. We report a case of a 74-year-old woman with a documented childhood history of penicillin allergy who was rechallenged with amoxicillin/clavulanate (Augmentin) in the hospital during admission. She was given one trial dose of amoxicillin/clavulanate for the treatment of urinary tract infection to cover organisms detected in the urine culture. Amoxicillin/clavulanate was determined to be the most suitable antibiotic for empirical treatment. Given a documented history of penicillin allergy from over 60 years ago, the likelihood of reactivity was suspected to be low to none. The patient, however, developed an allergic reaction after the one-time oral amoxicillin/clavulanate 875/125 mg dose trial.