Prevalence of Inducible Urticaria in Patients with Chronic Spontaneous Urticaria: Associated Risk Factors

BackgroundInformation on the prevalence of inducible urticaria (IU) in patients with chronic spontaneous urticaria (CSU) and the factors affecting this prevalence is scarce in the literature.ObjectivesTo estimate the frequency of IU in patients with CSU and to explore possible factors associated with CSU.MethodsPatients older than 12 years diagnosed with CSU and a control group with no history of urticaria were recruited from 2 different cities. All patients were questioned about triggers associated with exacerbation of urticaria, and challenge tests were performed for symptomatic dermographism, pressure, cold, water, and exercise. Atopy to mites and self-reactivity to autologous serum were evaluated using skin tests.ResultsThe study population comprised 245 patients with CSU and 127 controls. Of the patients with CSU, 186 (75.9%) reported a physical trigger, although only 89 (36.3%) had a positive challenge test result. The challenge tests showed that symptomatic dermographism was the most common type of IU, affecting 24.8% of the CSU group, followed by cold, which affected 13.4%. In the control group, 3.9% of patients were positive for symptomatic dermographism. People living in Medellín city had a higher frequency of symptomatic dermographism 28.5% (odds ratio, 2.1; 95% CI, 1-4.4; P = .03) and cold urticaria 16.5% (odds ratio, 3.3; 95% CI, 1.125-9.8; P = .02) than did people living in Bogotá (dermographism 14.4% and cold 5.2%). Atopy and self-reactivity were more frequent in patients with CSU than in the control group.ConclusionsPhysical triggers must be verified by challenge tests to avoid unnecessary lifestyle restrictions. Environmental factors such as geographical characteristics could play a key role in the development of some types of IU, whereas atopy and self-reactivity are major risk factors for CSU.