People are drinking worm larvae in the hope it will improve their health. Research into use of parasites to treat illness is promising, but some doctors aren’t so sure.

Would you pay thousands of dollars and leave the country just so you could get a parasitic infection on purpose?

Intentionally ingesting worms may sound creepy but for some people with multiple sclerosis, celiac disease, or severe allergies, the prospect sounds more promising than gross. Studies have shown that people who have or have recently had parasites in their bodies are less likely to develop autoimmune diseases. Clinical trials with ulcerative colitis and Crohn’s disease patients showed reduced disease activity after exposure to intestinal parasites.

Advocates say parasitic infections can reset the immune system, preventing it from going haywire and attacking healthy tissues as it does in many autoimmune diseases.

Parasitic worms are called helminths. Although approved for clinical trials, helminthic treatment –or “worm therapy”–is not yet available in the United States. In fact, it’s illegal.

That doesn’t stop people from doing it on their own or traveling to other countries to give it a try. Some swear by it and researchers are excited about it, but scientists say we still have a lot to learn.

Read More: Get the Facts on Hookworm Infections »

Indoor toilets and sanitary drinking water certainly make life more pleasant. These and other hygienic habits help improve our health in a lot of ways, including drastically lowering our chances of getting parasitic infections.

In regions without proper sanitation, parasites thrive in people and animals, who get infected and reinfected. Hookworm eggs, for example, survive in soil and can be transmitted on foods like fruits and vegetables that haven’t been washed thoroughly.

That’s why the risk of parasitic infection is much higher in underdeveloped countries.

You might think that having parasitic worms living in your intestines would make you sick, and they most certainly can; symptoms may include diarrhea, vomiting, abdominal pain, and blood loss. But it is also possible to have a few parasites taking up residence in your gut without even knowing it.

Dr. Amesh A. Adalja is an infectious disease physician at the University of Pittsburgh. He told Healthline that parasites stimulate a specific type of response from the immune system (Th2 response). He explained that it alters its polarity away from another type of response (Th1) that is seen in autoimmune diseases.

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According to the “hygiene hypothesis,” fewer parasitic infections in the developed world has resulted in a higher rate of allergies and autoimmune diseases.

The theory goes that humans need parasites to help train our immune systems. By ridding our environment of germs, we may be shortchanging our immune systems.

A 2012 Brigham and Women’s Hospital study found evidence to back up the hygiene hypothesis. The researchers compared the immune systems of mice living in germ-free environments to those living in normal environments. The germ-free mice showed exaggerated inflammation of the lungs and colon. That’s similar to what happens in asthma and colitis.

When researchers exposed young, germ-free mice to microbes, it normalized their immune systems. Even better, it turned out to have a long-lasting benefit.

“These studies show the critical importance of proper immune conditioning by microbes during the earliest periods of life,” the study authors said in a press release.

According to Adalja, “The hygiene of modern civilization may have led to the trading of one type of disease (parasitic infectious disease) for another (autoimmune). Untangling the nuances of the immune response to parasites has provided more evidence for the hygiene hypothesis.”

Read More: Hookworms as a Treatment for Crohn’s Disease »

Researchers around the world are exploring the role parasites may play in treating disease.

Australia’s National Health and Medical research Council recently awarded $860,000 to scientists studying hookworms for treatment of celiac disease.

When people with celiac disease consume gluten, the immune system gets confused and overreacts, attacking the small intestine. Researchers Dr. John Croese and Paul Giacomin, Ph.D., want to see if hookworms can stifle that immune system response.

To do that, they’ll inject 40 celiac disease patients with hookworm larvae.

Their previous clinical trial involved 12 adults with celiac disease. Those participants were infected with hookworm larvae and followed for a year. During that time, they slowly increased the amount of gluten in their diets.

By the end of the trial, eight participants were able to eat the amount of gluten contained in a medium-sized bowl of spaghetti. For someone with celiac disease, that’s a big deal.

For the new trial, the researchers will raise gluten levels even higher.

Hookworms don’t multiply within the body, but they do secrete proteins. Scientists are working on isolating those proteins. Then they can try to determine if they have anti-inflammatory properties. If they’re successful, those proteins could be used for treatment of a variety of diseases.

If you’re dealing with debilitating symptoms of chronic illness, you may be tempted to give parasites a try.

Adalja advises against going it alone.

“For those with refractory autoimmune diseases, or part of clinical research, it might be an avenue worth exploring with a healthcare professional,” he said. “Parasitic infections are not always benign. The risks, as well as the potential benefits, should be explored in detail before undertaking this course of therapy.”

Dr. Saurabh Mehandru, an assistant professor of medicine and gastroenterology at the Icahn School of Medicine at Mount Sinai in New York, told Healthline there are potential side effects of infecting yourself with parasites.

These include minor intestinal problems, chronic anemia, and nutritional disorders. It can even cause you to develop abscesses or cysts. These could have serious health consequences.

Mehandru doesn’t consider it a promising therapy. He points to a recent Cochrane systematic review that concluded, “Currently, there is insufficient evidence to allow any firm conclusions regarding the effectiveness and safety of helminths used to treat patients with IBD.”

Study authors noted their review was based on one small study and further research is needed.

“It is my opinion as well,” said Mehandru, “that we do not have sufficient evidence that ‘worm therapy’ works, while there may be significant side effects.”

Through more clinical trials, researchers hope to learn more about the safety and effectiveness of helminths in treating illness.