Eggs from the pig whipworm Trichuris suis (TSO) reduce the symptoms of Crohn’s disease and ulcerative colitis, which are both inflammatory bowel diseases – but why? At the moment, no-one is quite clear, but researchers at NYU School of Medicine are starting a clinical trial to try to find out – if you are in the US and want to join, the details about the trial are here. It may be that the parasites change the quantity and type of bacteria that are attached to the intestinal wall.

Hookworms seem to cure allergies – this could be down to the hygiene hypothesis, where life is now so ‘clean’ that the immune system doesn’t have enough to do and attacks the body.