Background: Penicillin allergy is the most commonly reported drug allergy and often presents with cutaneous symptoms. Other common diagnoses, such as chronic urticaria, may be falsely attributed to penicillin allergy. Because chronic urticaria is fairly common in the general population, evaluation of its prevalence in patients with self-reported penicillin allergy was of interest. Similarly, the prevalence of self-reported penicillin allergy in patients with chronic urticaria is not well known and also becomes interesting in light of the high prevalence of self-reported penicillin allergy in the general population.

Objectives: To determine the prevalence of self-reported penicillin allergy in patients with chronic urticaria and the prevalence of chronic urticaria in patients with self-reported penicillin allergy.

Methods: This was a retrospective medical record review of 11,143 patients completed using the electronic health record of the University of Pennsylvania Allergy and Immunology clinic.

Results: The prevalence of self-reported penicillin allergy in patients with chronic urticaria was found to be approximately 3 times greater than in the general population. The prevalence of chronic urticaria in patients with self-reported penicillin allergy was also found to be approximately 3 times greater than in the population.

Conclusion: This link between chronic urticaria and self-reported penicillin allergy highlights the need for clinicians to inquire about self-reported penicillin allergy in patients with chronic urticaria and to consider penicillin skin testing. Furthermore, patients who report penicillin allergy might actually have chronic urticaria, indicating the importance of inquiring about chronic urticaria symptoms in patients with self-reported penicillin allergy.