Irritable bowel syndrome (IBS) is a chronic disorder of the intestines. IBS does not cause inflammation and does not lead to a more serious condition.

The cause is unknown. With IBS, the muscles in the colon do not work normally and may spasm. If you have IBS, your colon may be more sensitive, reacting strongly to food and medication. Food allergies and certain bacteria may add to the symptoms. IBS may also occur after having the stomach flu (called gastroenteritis).