Gas in the digestive tract occurs in all people. This gas is composed mainly of oxygen, carbon dioxide, nitrogen, hydrogen and, occasionally, methane. It is released through the mouth by burping (belching) or through the rectum (flatulence).

Bloating refers to an unpleasant sensation of fullness or swelling in the abdomen. It may result from many causes, including an accumulation of gas in the stomach and intestines. Abdominal pain often accompanies bloating.

Most gas in the stomach is swallowed (usually during a meal). Much of this gas is eliminated by burping, and very little enters the large intestine. However, gas within the large intestine is created when harmless bacteria consume undigested foods. The action of these bacteria causes the unpleasant odor in gas.

Most people who believe they produce (and pass) too much gas actually produce the same amount as others. The average person produces between one and four pints (about 0.5 to 1.9 liters) of gas per day, and passes the gas 14 to 23 times a day.

Patients whose gas and bloating is accompanied by recurrent, severe or prolonged abdominal pain should seek medical attention because this may indicate the presence of another underlying condition (e.g., irritable bowel syndrome) – especially if they also experience bleeding, nausea, vomiting, fever or weight loss. The physician will perform a physical examination and compile a thorough medical history. Screening tests (e.g., endoscopy) may also be conducted to help determine the cause of gas and bloating.

Most gas symptoms that are unrelated to a medical condition are usually brief. Because of this, gas is often treated conservatively by minimizing further symptoms with lifestyle changes or over-the-counter gas-reducing products.

Problems caused by gas can often be relieved by identifying and eliminating the factors that cause the gas. When using medications, it is generally considered best to experiment with only one gas-reducing product at a time. Exercise (e.g., walking, jogging) helps to stimulate the passage of gas through the digestive tract, easing symptoms.