Association of alopecia areata with atopic dermatitis and chronic spontaneous urticaria

Background: Epidemiologic studies report that alopecia areata (AA) is related to various atopic and autoimmune diseases. The purpose of this study was to identify clinical characteristics and the prevalence of comorbid conditions in Israeli patients with AA. Methods: This retrospective, matched, case-control study was based on data from an electronic patient record data base. The patients with an electronically documented diagnosis of AA were included in the AA group. The control group was randomly sampled from the remaining subjects, with a case-To-control ratio of two controls for each case. Comorbidity was compared between the study groups. Results: A total of 1751 subjects (49.4% men and 50.6% women), ages 34.9 ± 17.8 years old, were identified. The control group consisted of 3502 age-and sex-matched subjects. The AA group was characterized by a higher blood eosinophil count (0.39 ± 0.12 cells/mm3) than the control group (0.31 ± 0.14 cells/mm³; p < 0.001). In the AA group, there was a higher prevalence of allergic rhinitis (odds ratio [OR] 2.15 [1.85-2.49]; p < 0.001), asthma (OR 1.57 [1.28 -1.93]; p < 0.001), atopic dermatitis (AD) (OR 4.17 [3.18 -5.47]; p < 0.001), and food allergy (OR 2.79 [1.58-4.91]; p < 0.001) than in the control group. The prevalence of organ-specific and systemic autoimmune diseases was significantly higher in the AA group than in the control group, with the OR of having any autoimmune disease calculated to be 4.72 (3.99 -5.57; p < 0.001). The OR of having chronic spontaneous urticaria (CSU) with AA was 6.15 (4.06 -9.32; p < 0.001). In patients with concomitant AA and CSU, allergic rhinitis and AD were more prevalent than in patients with CSU in the control group. Conclusion: An estimated prevalence of AA among an Israeli population was ∼0.8%. The novel finding of our study was the high prevalence of food allergy and CSU in patients with AA.