Abstract: Objective: To determin the relationship between gut microbiota and alopecia areata, and to provide reference for early prevention and disease improvement of alopecia areata. Methods: The study selected significant SNPs associated with gut microbiota as instrumental variables and used the inverse variance weighted (IVW) method as the primary analysis method for assessing causal effects. Heterogeneity of the genetic instrumental variables was evaluated with Cochran's Q test, and pleiotropy was assessed with the MR-Egger intercept test and the MR-PRESSO test. Sensitivity of the causal relationship between SNPs and alopecia areata was evaluated using the leave-one-out approach. Results: The inverse variance weighted method showed that the Lachnospiraceae family group 3-1-46FAA, Dialister genus, Paraprevotella genus, Ruminococcus genus lactaris group, Dialister invisus group, and the PWY.6731 pathway microbiota were negatively correlated with alopecia areata; the PWY0.1415 pathway microbiota, Bacteroidetes phylum, Bacteroidales order, Bacteroidia class, Bacteroides genus caccae group, and PWY.5686 pathway microbiota were positively correlated with alopecia areata; Mendelian randomization results showed a positive correlation between alopecia areata and the Bacteroidales order, Bacteroidia class, and Bacteroidetes phylum; Sensitivity analysis: The MR-Egger intercept test and MR-PRESSO test indicated no horizontal pleiotropy, and the heterogeneity test showed no heterogeneity in their relationship, with the leave-one-out analysis yielding robust results. Conclusion: The gut microbiota of Bacteroides were associated with alopecia areata.

Key words: alopecia areata, gut microbiota, Mendelian randomization