Irritable bowel syndrome (IBS) is a disorder of the large intestine (colon) that happens when the bowel overreacts to a mild stimulus. The stimulus may be certain foods (wheat, dairy products, citrus fruits, beans, cabbage, milk and carbonated drinks), and can be aggravated by stress. There are 3 types of IBS based on symptoms: constipation-predominant (IBS-C), diarrhea-predominant (IBS-D), and IBS with mixed bowel habits (IBS-M). Basic symptoms of IBS include abdominal pain/cramping while passing a bowel movement, urge to move bowels but inability to do so, excessive belching and flatulence, bloating, unusual bowel movements – intermittent diarrhea and/or constipation, changes in frequency of bowel movements. More severe symptoms are weight loss, diarrhea at night, rectal bleeding, iron deficiency anemia, unexplained vomiting, occasionally heartburn, and difficulty swallowing. The exact cause of IBS is not known, but it may occur due to stronger and longer muscle contractions in the intestine, nervous system abnormalities – poor communication between the brain and the intestines can cause the body to overreact to the normal digestive process, serious infection after gastroenteritis caused by bacteria or a virus, and changes in gut microbiome. IBS is a common disorder that affects many people, but the risk factors are gender (females are more prone to IBS), age (people under age 50), genetics, environmental factors, and a history of sexual, physical or emotional abuse. IBS is diagnosed by a doctor through a complete medical history, physical exam and other tests. Laboratory tests such as lactose intolerance tests, breath tests for bacterial overgrowth, and stool tests are also done to rule out other conditions such as lactose intolerance, diabetes or chronic diarrhea. Diagnostic procedures may include colonoscopy, X-ray, CT scan, upper endoscopy. Treatment of IBS involves avoiding foods that trigger symptoms, eating high-fiber foods, staying fully hydrated, engaging in regular physical activity, and getting adequate sleep. Specifically, it is recommended to avoid high-gas foods (carbonated drinks and certain foods), gluten, and FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) found in some grains, vegetables, fruits and dairy products. It may be necessary to consult a dietitian to assist with dietary changes. Medications may be required to alleviate symptoms, such as fiber supplements, laxatives, anti-diarrheal medications, anticholinergic medications, and antidepressants.