Parasites. When you start getting rid of parasites in 3rd world communities, auto immune issues start to crop up. It's thought that since the body isn't fight

Parasites. When you start getting rid of parasites in 3rd world communities, auto immune issues start to crop up. It's thought that since the body isn't fighting off parasites then it sits idle and starts attacking itself. It kind of makes sense from a purely evolutionary perspective. There's actually been treatments for some auto immune diseases that involve giving a relatively harmless parasite to people.