Abstract: Objective: To analyze the potential causal associations between three atopic diseases (asthma, atopic dermatitis, and allergic rhinitis) and the risk of developing alopecia areata using two-sample Mendelian randomization. Methods: Summary statistics from the genome-wide jiaoassociation studies (GWAS) were employed. Single nucleotide polymorphisms (SNPs) significantly associated with asthma, atopic dermatitis, and allergic rhinitis were used as instrumental variables. The casual relationship was assessed with five methods: the inverse variance weighted (IVW), MR-Egger regression, weighted median, simple mode and weighted mode methods. The results of analyses were presented with odds ratio and 95% confidence interval. Results: 64 SNPs related to asthma, 61 SNPs related to atopic dermatitis, and 3 SNPs related to allergic rhinitis were selected as instrumental variables. The IVW method showed that asthma and atopic dermatitis were both risk factors for alopecia areata (OR: 1.45， 95% CI: 1.67-1.97; OR: 1.79，95% CI: 1.28-2.51)，weighted median and weighted mode also supported the significance of causal associations. Conclusion: Mendelian randomization analyses indicated positive causal associations between atopic diseases asthma, atopic dermatitis and alopecia areata.

Key words: alopecia areata, asthma, atopic dermatitis, allergic rhinitis, mendelian randomization