Title: High Prevalence of Drug Allergy in Patients with Urticaria and Angioedema
Abstract: While allergic reactions to drugs can be a cause of acute urticaria and angioedema, the frequency of patient-reported drug allergies in chronic urticaria and angioedema has not been explored. The prevalence of adverse drug reactions in the general population is 7%. We aim to determine the prevalence of patient-reported drug allergies in patients with chronic urticaria and/or angioedema. We hypothesize that prevalence of reported drug allergies in this population will be higher than the general population. We retrospectively identified patients with chronic idiopathic urticaria and angioedema seen in a university allergy immunology clinic from September 2007-2017. We classified patients as comorbid urticaria and angioedema (CUA), isolated urticaria (IU), or isolated angioedema (IA) and collected data on patient-reported drug allergies. Patients with ACE-inhibitor induced angioedema were excluded from analysis. 451 patients with urticaria and/or angioedema were identified. Drug allergies were reported in 62% (n=280). Patients who reported drug allergies were older (median 47 vs. 36 years, p<0.001) and had higher BMI (median 28.3 vs. 26.6, p=0.002). There was no difference by gender (p= 0.57). Patients with IA had the highest frequency of reported drug allergy (76%), significantly higher than CUA (60%) and IU (57%) (overall p=0.007). Allergy to >1 drug was reported in 171 patients (38%). The frequency of multiple drug allergy did not differ by subgroup (p=0.26). Our study suggests that patients with idiopathic urticaria and/or angioedema have a much higher reported frequency of drug allergy than the general population. Further studies are needed to explore these findings.