Turkalj M, Drkulec V, Haider S, et al. - This study was undertaken to determine if bacterial load in drinking water was correlated with altered risk of allergic diseases. Between 2011 and 2013, the authors enlisted 1,110 schoolchildren (aged 6 to 16 years) in Požega‐Slavonia County in Croatia, where they capitalized on a natural experiment in which individuals receive drinking water through public mains supply or through individual wells. Findings revealed that there was a higher cumulative bacterial load in drinking water and a significantly lower lifetime prevalence of allergic diseases among children with individual supply. In the quantitative analysis, the risk of allergic diseases decreased significantly in the first year of life, with increased bacterial load in drinking water. The results suggested that high commensal bacterial content can protect against allergic diseases in drinking water.