Environmental factors have an effect on the onset and progression of inflammatory bowel disease (IBD). A new study published in Nature combines an integrated systems approach, consisting of zebrafish, mouse models and chemical databases, with machine learning to investigate the effect of environmental factors on intestinal inflammation. The approach found that propyzamide, a common herbicide, targets a T cell and dendritic cell signalling pathway (AHR–NF-κB–C/EBPβ) that regulates intestinal inflammation.