There is a special issue of Nature Outlook on IBD flagged up today which is Open Access. Several of the articles could be of some interest to evolutionary medics who are interested in the gut microbiota and commensal helminths and their role in modulating the human immune system. Articles of special interest are one on the possibility of microbiota engineering via faecal transplants for curing IBD, and an interview with helminth therapy pioneer Joel Weinstock on his latest interpretation of the mechanisms by which helminths exert control over the immune system.