IBS is a functional disorder. Even though the digestive tract looks normal, it doesn't function as it should. Muscles in the intestines move food from the stomach to the rectum. Normally, they contract and relax in a gentle rhythm that moves the food along in a fairly predictable schedule. But with some people, the muscles in the intestines spasm. That means the contractions are longer and stronger than normal. Those spasms are painful. They also disrupt the movement of food through the intestines. If they slow it down, you become constipated. If they cause it to move through too quickly, you get diarrhea. It's not unusual for people to alternate between the two. Another cause of discomfort for people with IBS results from oversensitive nerve endings in the digestive tract. Small bubbles of gas that wouldn't bother most people might be quite painful for you. Your heightened sensitivity can also lead to swelling and bloating.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email.

Sept. 14, 2022