You are what you eat

This article from BBC about helpful parasites seems slightly horrifying. Why would hookworms be helpful? Perhaps for the same reason that leaches are still useful for draining blood from congested areas, or perhaps there's some handy chemical the hookworms use to suppress the body's reaction that we might be able to isolate. I'd prefer that, myself. After all, hookworms do cause some damage.

I'm not an expert, but what I've read seems to fit a "bored army" model for some immune disorders. The immune system is supposed to be sensitive, and if you don't give it enough to do it can become hair trigger sensitive, and start going after our "slightly odd" (but necessary) cells. Or to describe it another way--every part of our bodies needs exercise to keep from deteriorating, though not so much exercise as to destroy us. Running is good, shin splints are bad. A mild cold doesn't hurt too much, malaria is bad news.

If that model is correct, then we need a little exposure to dirt to keep us "in fighting trim," but not so much that we damage ourselves. I have no prescription for how to do that. Having kids play outside and maintaining basic waste sanitation (our own wastes are more likely to infect us than those of other creatures) seems like a nice rough and ready set of rules. (Yes, I know about river blindness, but I live in Wisconsin.)