For 20 years, Carol Epstein passed up coffee, salads, dairy and wheat because she feared the consequences.

"Stomach cramps and you might have diarrhea with it," she said.

It didn't keep carol home, but irritable bowel syndrome followed her on vacations to Egypt, Cambodia, India. Nothing helped, not even a restrictive diet. Then she met Dr. Mark Pimentel.

A breath test found an overgrowth of bacteria in Carol's stomach. Working on the theory that bacteria may cause IBS, Dr. Pimentel tested the antibiotic rifaximin on 87 patients. Nearly 40 percent saw major improvement.

"If you take the antibiotic for 10 days, patients got better, and they got better for 10 weeks after the antibiotic was stopped," he said.

Unlike other antibiotics, rifaximin is not absorbed into the bloodstream. It stays in the intestine, killing bacteria before passing through the digestive tract.

"Just to have the feeling that I'm going to eat something and not going to have cramps or run to the bathroom or have this trapped gas is a wonderful feeling," said Carol.

Carol's been pain-free for a year and a half.

Patients take the antibiotic for just 10 days, but the effects seem to last up to a year. A longer study is needed to verify the results.

The drug is FDA approved to treat traveler's diarrhea and is available by prescription under the brand name Xifaxan.