In a previous paper published in this journal, we reported on the role of the intestinal microbiota in the development of atopic manifestations, as examined in a prospective birth cohort (KOALA).1 We showed that infants colonised with Clostridium difficile were at increased risk of developing eczema, wheeze and sensitisation. An association between C difficile and atopic diseases has also been reported by others.2 3

A possible underlying mechanism could be through breaking oral tolerance, as C difficile can cause inflammation in gut tissues, leading to increased permeability of the mucosal barrier and thus facilitating the penetration of allergens.4 The enteropathogenicity of C difficile is associated with the production of toxins A and B, encoded by the genes tcdA and tcdB. Both toxins disrupt epithelial cell tight junctions and thereby ablate epithelial barrier function.5 According to the hypothesised mechanism, it is expected that …