When Parasites Help

Some parasites calm the immune system because a host that dies too fast is bad real estate. That led scientists to test whether helminths could help inflammatory disease.

The evidence is still early and mixed. Small studies have explored safety, immune changes, and possible benefits, but controlled parasite therapy is not an approved treatment for Crohn's disease or multiple sclerosis.

This idea is sometimes called the hygiene or old-friends hypothesis: immune systems evolved around constant microbial and parasitic exposure, and losing some exposures may affect regulation.

But a parasite is still a parasite. The useful lesson is narrower: worm molecules and immune pathways may inspire therapies without asking patients to carry live infections.