The association between domestic hard water and eczema in adults from the UK biobank cohort study

To examine the association between domestic hard water supply and eczema prevalence and incidence in middle‐aged adults and the contextual effect on eczema outcomes by postcodes in adults in the UK. Increasing levels of domestic hard water, as measured by CaCO3 concentrations, were associated with an increased prevalence of eczema in adults but not increased incidence. Ongoing efforts to reduce hard water exposure may have a beneficial effect in reducing the burden of eczema in adults. Further research is needed to explore area-level factors that may lead to eczema.