Patients with self-reported penicillin allergy demonstrate increased rates of chronic urticaria compared with rates observed in the general population, suggesting that the urticaria may be the true condition behind the perceived allergy, according to a study presented here at the 2015 Annual Meeting of the American Allergy Asthma and Immunology (AAAAI).
"Given the disparity between the prevalence of chronic urticaria in patients with self-reported penicillin allergy and the prevalence of chronic urticaria in the general population, the study findings suggest that some patients with chronic urticaria may be mistakenly attributing their urticaria to penicillin allergy," explained lead author Susanna G. Silverman, MD, University of Pennsylvania, Philadelphia, Pennsylvania, speaking here on February 24.
Skin testing and oral challenges typically show that most patients in fact do not have a true immunoglobulin E (IgE)-mediated allergy to penicillin, although approximately 10% of the general population report penicillin allergy, Dr. Silverman explained.
She and her colleagues evaluated charts on all patients seen at the university's Allergy and Immunology clinic from June 2007 through August 2014 who were age 18 years or older and who were identified as having allergies to penicillin, amoxicillin, amoxicillin-clavulanate, or piperacillin-tazobactam.
The researchers found that, among 1,419 patients self-reporting with penicillin allergy, 175 patients (84% female; age range: 20 to 92 years) also showed a diagnosis of chronic urticaria. The prevalence of chronic urticaria in the cohort of patients reporting penicillin allergy was 12.3% -- significantly higher than the estimated 0.5% to 5% prevalence of chronic urticaria in the general population.
Self-reporting of penicillin allergy should raise a red flag to clinicians of the possibility of chronic urticaria, Dr. Silverman concluded, suggesting that physicians ask such patients about symptoms of chronic urticaria.