There's an awesome NYTimes article about coevolution, and the necessity of parasites.Our immune systems developed under a pretty heavy parasitic load, and are built to handle those parasites. Now that we've cleaned up most of our worms and bacteria our relatively unchallenged immune systems basically get bored, and start going after inappropriate targets within our bodies. (This is a good argument for the five-second rule, and for eating street vendor food - keep that immune system properly occupied so it doesn't go looking for trouble.)Anyway, they have actual studies and statistics:About 10 years after improved hygiene and deworming efforts reduced worms in a given population, I.B.D. (Inflammatory Bowel Disease) rates jumped. Weinstock had his hypothesis: after a long coevolution, the human immune system came to depend on the worms for proper functioning. ...epidemiologists had already dubbed this notion "the hygiene hypothesis": as improved hygiene reduced exposure to certain infectious agents, the immune system began malfunctioning. By the late 20th century, autoimmune disorders, characterized by the body's defenses attacking some aspect of the self, had increased markedly, and allergic diseases, defined by an overblown immune response to nonthreatening substances, afflicted almost half the people in the developed world.If eliminating worms led to an increase in disease, could re-introducing worms actually treat these diseases? In mice, the answer was yes. Worms were used to "inoculate" against mouse asthma, Type 1 diabetes, multiple sclerosis and I.B.D.In 2005, he published results from two human studies. After ingesting 2,500 microscopic T. suis eggs at 3-week intervals for 24 weeks, 23 of 29 Crohn's patients responded positively. (Crohn's disease belongs to the I.B.D. family, which also includes ulcerative colitis.) Twenty-one went into complete remission. In the second study, 13 of 30 ulcerative colitis patients improved compared with 4 in the 24-person placebo group.Scientists around the world are intrigued. Several large studies are under way. If you decide to try this at home, please document the project for Instructables!