Associations between vitiligo and allergic diseases: a bidirectional two-sample Mendelian randomization study

Background Growing evidence shows a significant association between vitiligo and several allergic diseases. However, the real causality remains unclear considering the susceptibility of epidemiological studies to residual confounders. Methods We conducted a bidirectional two-sample Mendelian randomization (MR) analysis to investigate the relationship between vitiligo and seven common allergic diseases including atopic dermatitis (AD), allergic rhinitis, allergic contact dermatitis, allergic conjunctivitis, allergic purpura, asthma and urticaria by leveraging publicly available genome-wide association study (GWAS) summary data. The selection of instrumental variables conformed strictly to a series of preset inclusion and exclusion criteria. The multiplicative random-effect inverse variance weighted (IVW) method was used to assess the causal association. The Cochran’s Q test, MR-Egger intercept test, and leave one-out analysis were conducted to identify heterogeneity and pleiotropy. Results Allergic contact dermatitis (OR 1.13, 95% CI 1.03–1.24, p = 0.013) and urticaria (OR 1.22, 95% CI 1.04–1.44, p = 0.016) contributed to developing vitiligo. On the other side, vitiligo showed protective effect on developing AD (OR 0.98, 95% CI 0.96-1.00, p = 0.015), allergic conjunctivitis (OR 0.98, 95% CI 0.95-1.00, p = 0.044), allergic rhinitis (OR 0.97, 95% CI 0.95–0.99, p = 0.017), allergic purpura (OR 0.91, 95% CI 0.83–0.99, p = 0.030) and asthma (OR 0.97, 95% CI 0.95-1.00, p = 0.033). Conclusions Our findings indicated causal effect of allergic diseases on vitiligo and protective role of vitiligo on developing allergic diseases, facilitating more comprehensive management for vitiligo patients with co-morbidities and dermatologists' assessment of patient prognosis.