early on, before heavy sanitation, people were exposed to more parasites and other microbes than today. apparently parasites modulate the immune system to not attack them, so this has a beneficial effect against AUTOimmune and by extension cancers. i think there is helminthic therapy going on, but i dont think its sanctioned in the medical field. of course it doesnt work with all parasites.(hookworm seems to reduce allergic ashtma). but parasites ascaris worms can trigger it, mainly because the worms travel to the airways and trigger irritation of the lungs.