There is a causal effect between AD and inflammatory bowel disease (IBD), but not between IBD and AD, according to a study published in Inflammatory Bowel Diseases. Christa Meisinger, MD, MPH, and colleagues, who aimed to determine whether AD is causally related to IBD and vice versa, conducted a two-sample Mendelian randomization investigation. Independent genetic instruments from the largest available genome-wide association study for AD (EAGLE eczema consortium without the 23andMe study; 10,788 cases and 30,047 controls) were used to examine the association with IBD in the UK Biobank study (7,045 cases, 456,327 controls) and a second European IBD sample (12,882 cases, 21,770 controls). AD was strongly associated with higher risk of IBD as a whole (OR, 1.107; 95% CI, 1.035-1.183) in the UK Biobank study. The positive association was not significant in the other IBD study (OR, 1.114; 95% CI, 0.956; 1.298), but in meta-analyses of results from both studies, the strong association could be confirmed (OR, 1.11; 95% CI, 1.04-1.18).