And it is one of the costliest medical problems in lost work time and productivity.
There is no cure, but doctors are hoping a tiny organism that comes from worms can help.
Amanda Dotter of Lehighton, Pa., has struggled with Crohn's Disease since 8th grade. It gave her on and off severe abdominal pain, making school difficult.
In fact, this year, she couldn't finish her freshman year at college.
"Being in pain, it just wears you down. It takes a toll on your body," she says.
In Crohn's Disease, a person's own immune system attacks the digestive tract, usually the inside of the small intestine.
It causes pain, fever, nausea or vomiting, diarrhea, and weight loss.
Amanda has tried medications. Many work at first but then symptoms come back.
So she's hoping to qualify for a test of a radically different approach. It's a nationwide study by Coronado Biosciences , being done locally by Dr. James Boylan of St. Luke's Hospital and Dr. Ronald Intelisano of South Jersey Medical Associates
The test is of a radically different approach - using worms.
That's right. Worms.
This experiment is to see whether the microscopic eggs of whipworms from pigs can slow or stop the attack on the intestines.
It's a take-off of the 'hygiene hypothesis," that modern life is too clean, and we're not being exposed to the germs our ancestors were.
Without those targets, the body attacks itself.
In countries where tiny parasites like whipworms are more common -
"These autoimmune diseases, such as rheumatoid arthritis, such as asthma, such as Crohn's Disease, are extremely rare," Dr. Boylan told us.
Half of those in the trial will drink a saline solution with purified versions of the eggs, while the other half will get plain saline solution.
It's hoped the body will go after the microscopic parasites, and not attack the intestines.
"It's kind of a natural approach to treating these diseases," he says. "And it's a new approach that's not been available commercially."
In early tests, three quarters of patients drinking the worm eggs had at least some response.
And no, you won't actually get worms inside your body.
Dr. Boylan assures everyone, "These are pig parasites. they don't adapt long-term to people. So they will not cause an infection."
If she gets into the trial, Amanda hopes for relief from the pain, and more freedom in what she eats.
"Almost what's a healthy diet for normal people is an unhealthy diet for me," she told us.
For more information on the TRUST trial, click here. The Crohn's and Colitis Foundation of America is also keeping close tabs on the trial.