I heard a story on OPB awhile back. It was about Jasper Lawrence, a man who discovered that people in third-world countries seldom suffer from allergies and auto-immune disorders, as compared to Americans. He traveled to West Africa and purposely infected himself with parasites…. hookworms. His allergies, once bad enough he couldn’t ride down the street without his eyes swelling shut, subsided.
An update to the story was posted in April 2010, after revisiting Jasper Lawrence. Here it here: http://www.radiolab.org/blogs/radiolab-blog/2010/apr/02/an-update-on-hookworms/
Check out this story, as well as other “Acts” about the “enemy” on This American Life here: Enemy Camp