Some parasites "turn down" the host's immune response, and evidence suggests that helminth infection can help patients suffering from allergies, asthma, inflammatory bowel disease, multiple sclerosis, and type 1 diabetes. Now, there is evidence that helminths could help treat obesity.
The myth that "natural is better" is widespread and pernicious. Though it can manifest in relatively harmless ways (e.g., consuming overpriced organic food), the relentless pursuit of all-things natural can be dangerous or even deadly. It is not an exaggeration to say that society's obsession with natural remedies is itself an illness. The latest weirdness comes from Germany, which according to New Scientist, is considering approval of parasite eggs as a food additive. After eating the eggs, little worms hatch, and people believe that these worms will cure them of their maladies. Most likely, they won't.