摘要Background:Both eczema and tumor are associated with immune disorders.Although several investigations have observed the rela-tionship between eczema and certain cancers,evidence for causality is lacking.Methods:We conducted a two-sample Mendelian randomization(MR)study to examine and explore the genetic association between eczema and pan-cancers.Upon satisfying the three core assumptions of MR,we analyzed the causality between eczema and 15 site-specific cancers utilizing an inverse variance weighted method.We verified the results through a series of sensitivity and reverse direction analyses.The exposure and outcome datasets were substituted from the FinnGen and genome-wide association studies catalog data-bases.A meta-analysis on primary and validation analyses was performed to combine the estimates of MR study.Results:Based on the MR analysis results,eczema was associated with an increased risk of lung cancer(odds ratio[OR]=1.0427,95％confidence interval[CI]=1.0082-1.0783,P=0.0148)and brain cancer(OR=1.0285,95％CI=1.0120-1.0452,P=0.0007)and de-creased risk of colorectal cancer(OR=0.9324,95％CI=0.8774-0.9909,P=0.0242)and malignant neoplasm of the kidney(OR=0.9323,95％CI=0.8834-0.9839,P=0.0108).The sensitivity analysis indicated that the results were stable and reliable,and the reverse MR analyses demonstrated no causation between the cancers of interest and eczema.Conclusions:Our results identified eczema as a genetic risk factor for lung and brain cancer and a protective factor for colorectal cancer and malignant neoplasm of the kidney.No connection was observed between eczema and other cancers.Further evidence from epide-miological and mechanistic studies is needed to elucidate these findings in detail.