For people suffering from debilitating autoimmune disorders such as multiple sclerosis, there is growing evidence that help may be at hand from an unusual source: parasitic worms.

In a U.S. study, early safety tests suggested the eggs of pig whipworms have anti-inflammatory properties, reducing the size of brain lesions in MS patients. A similar trial is under way in Denmark. And in Britain, academics at the University of Nottingham are studying the potential health benefits...