Some allergic responses, such as atopic dermatitis, are inversely correlated with the occurrence of some types of cancer. To more clearly understand this correlation, Cipolat et al. induced tumours using DMBA–TPA in mice that lack three barrier proteins (EPI mice) and thereby model what occurs in some cases of atopic dermatitis. They found that these mice were resistant to developing benign tumours and this was associated with an exaggerated immune response on TPA administration. The authors suggest that this protective affect might arise from keratinocytes signalling to the immune system, which induces a protective immune response.