Everyone has gas. Most people produce about 1 to 4 pints a day and pass gas about 14 times a day. Passing gas through the mouth is called belching or burping. Passing gas through the rectum is called flatulence. Most of the time gas does not have an odor. The odor comes from bacteria in the large intestine that release small amounts of gases that contain sulfur.

Gas in the digestive tract comes from two sources: air that you swallow and the breakdown of undigested food by bacteria in the large intestine. Certain foods may cause gas. Foods that produce gas in one person may not cause gas in another. Drinking lots of water and non-fizzy drinks and chewing food more to lessen the amount of air you swallow when you eat can help reduce gas. For people with lactose intolerance, avoiding milk products will help.