Objective To explore the causal association between immune cells and allergic rhi-nitis using Mendelian randomization(MR)approach.Methods GWAS data for 731 types of im-mune cells and allergic rhinitis were obtained from genome-wide association study(GWAS)databas-es.A two-sample bidirectional MR analysis was conducted,with the inverse-variance weighted(IVW)method as the primary analytical approach,and the weighted median method,MR-Egger re-gression,simple mode method,and weighted mode method as supplementary approaches.Sensitivity analyses,including heterogeneity tests,pleiotropy tests,and the leave-one-out method,were per-formed.Bonferroni correction was applied to the preliminary results to enhance their reliability and rigor.Results The two-sample forward MR analysis revealed correlations between 67 immune cell phenotypes and allergic rhinitis.After Bonferroni correction,four immune cell phenotypes were finally identified.Among them,the expression of CD3 on CD39-positive activated CD4 regulatory T cells(OR=0.953,95％CI,0.931 to 0.978,P＜0.001,Padj=0.007),the expression of herpesvirus entry mediator(HVEM)on CD45RA-negative CD4+T cells(OR=0.965,95％CI,0.948 to 0.983,P＜0.001,Padj=0.008),and the percentage of human leukocyte antigen class DR(HLA-DR)-high-expressing monocytes among leukocytes(OR=0.929,95％CI,0.885 to 0.974,P=0.002,Padj=0.157)were protective factors for allergic rhinitis.In contrast,the percentage of transitional B cells among B cells(OR=1.094,95％CI,1.032 to 1.161,P=0.003,Padj=0.183)was a risk factor for allergic rhinitis.The reverse MR analysis showed no causal relationship between allergic rhinitis and the four immune cell phenotypes.Conclusion The two-sample forward MR analysis confirms a caus-al link between immune cells and allergic rhinitis.MR analysis has the advantages of reducing con-founding factor interference and avoiding reverse causation,providing a theoretical basis for in-depth research on immune mechanisms,sensitive biomarkers,and drug treatment targets of allergic rhinitis.