Could a Worm a day, Keep the Doctor away?

Swallowing the eggs of parasitic worms may seem the polar opposite of modern medicine. A growing body of research, however, is examining the stomach-turning possibility that parasites affect the immune system in a way that may protect against multiple sclerosis, inflammatory bowel disease, and other modern-day disorders.

Certain parasites have dwelled in people’s guts through much of human history.

Clinical trials are beginning to test whether intestinal worms have an effect on conditions such as food allergies and Crohn’s disease — problems blamed on a haywire immune responses. And researchers are trying to unravel exactly what worms do in the gut, in the hope that drugs could be developed to mimic the beneficial effects.

In the most recent work, published last week in the journal Science Translational Medicine, scientists followed a person with ulcerative colitis who saw his symptoms disappear after he swallowed the eggs of an intestinal parasite.