Investigating the Causal Relationship Between Gut Microbiota and Allergic Conjunctivitis: A Two-Sample Mendelian Randomization Study

To investigate the causal association between gut microbiota and allergic conjunctivitis. A two-sample Mendelian randomization (MR) analysis was performed using the summary statistics of gut microbiota (18,340) from MiBio-Gen consortium and allergic conjunctivitis data (<i>n</i> = 218,792) obtained from the IEU Open GWAS project. F-statistics and sensitivity analyses were used to address potential biases and ensure the reliability of our findings. Reverse MR analysis was conducted to assess the possible of reverse causal relationships. The inverse variance weighted estimates revealed the protective potential of the phylum Euryarchaeota against allergic conjunctivitis (OR = 0.87, <i>p</i> = 6.17 × 10⁻⁴). On the other hand, the genus Christensenellaceae R.7 group (OR = 0.75, <i>p</i> = 2.89 × 10⁻³), family Peptostreptococcaceae (OR = 0.83, <i>p</i> = 6.22 × 10⁻³), genus Lachnospiraceae FCS020 group (OR = 0.82, <i>p</i> = 0.02) all showed a suggestive protective association with allergic conjunctivitis. Additionally, sensitivity analysis confirmed the robustness of the above associations. In the reverse MR analysis, no significant causal association was found between gut microbiota and allergic conjunctivitis. This study has revealed a potential causal correlation between the phylum Euryarchaeota and allergic conjunctivitis, offering new insights to improve prevention and treatment of this condition.