One major hypothesis of evolutionary biology is that humans used to live in a far less hygenic environment and in particular have an immune system designed to ward of parasitic worms (with a reboot of the gut microbiology being the true purpose of the appendix). The growing tide of auto-immune diseases, including inflammatory bowel disease (IBD), may be a product of the immune system being primed to wipe out these invasive agents and lacking a true target. This hygene hypothesis may also be behind the rise of problem allergies.
University of Iowa researchers have had success in treating patients with the autoimmune disease IBD for twenty-four weeks "with "cocktails" laced with microscopic whipworm eggs. . . . After 24 weeks of worm therapy, 23 of the 29 volunteers went into remission." This is despite the fact that the volunteers had no success with other therapies.
This joins a number of other therapies (e.g. "gut bacteria transplants" that involve putting other people's fecal materials into one's gut with depleted gut bacteria resources, and maggot therapy with decontaminated maggots let loose to eat dead tissue on a person since they don't eat live tissue and are mostly a worry because they carry diseases), that are gross but seem to work.