Small intestinal bacterial overgrowth (SIBO) occurs when an abnormally high number of bacteria that normally only occur in the large intestine colonize the small intestine. These bacteria ferment carbohydrates in the upper digestive tract and produce gases such as hydrogen, methane or hydrogen sulphide. This can lead to flatulence, diarrhea, constipation and other digestive problems. SIBO is a common cause of chronic gastrointestinal complaints and is often associated with irritable bowel syndrome:Causes, Symptoms & Holistic Ways to Relieve. Timely diagnosis and targeted treatment are crucial for healing.