Gas or "intestinal gas" means different things to different people. Everyone has gas and eliminates it by belching or passing it through the rectum, medically referred to as flatulence (slang, farting).
The ability to belch is almost universal. Belching, also known as burping, is the act of expelling gas from the stomach out through the mouth. The usual cause of belching is a distended (inflated) stomach caused by swallowed air. The distention of the stomach causes abdominal discomfort, and the belching expels the air and relieves the discomfort. The common reasons for swallowing large amounts of air (aerophagia) are gulping food or drink too rapidly, anxiety, and carbonated beverages.
Excessive air in the stomach is not the only cause of belching. For some people, belching becomes a habit and does not reflect the amount of air in their stomachs. For others, belching is a response to any type of abdominal discomfort and not just to discomfort due to increased gas.
Most people produce 1 to 3 pints of intestinal gas in their large intestines (colons) every 24 hours and pass gas an average of 14 times a day. The gas is made up primarily of carbon dioxide, hydrogen, and in some families, methane, that is mixed with nitrogen and oxygen from room air that is inhaled or swallowed. The carbon dioxide, hydrogen, and methane are produced by bacteria in the large intestine while they digest undigested food that reaches the large intestine. Although these gases are odorless, the bacteria also may produce small amounts of sulfur-containing gases that are foul-smelling. It is important to distinguish between increased flatulence (farting) and foul-smelling flatulence.
Bloating is the subjective sensation (feeling) that the abdomen is larger than normal. Thus, bloating is a symptom akin to the symptom of discomfort. In contrast, distention is the objective determination (physical finding) that the abdomen is actually larger than normal. Bloating and distention may be due to increased amounts of gas in the abdomen, but there also are other causes. Sometimes intestinal gas that is associated with bloating can be accompanied by
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.
Pictures, Images, Illustrations & Quizzes
Digestive Disorders: Common Misconceptions
Learn about the digestive system and common misconceptions of digestive disorders. Read about what causes ulcers, heartburn,...
Stomach Pain Quiz: Nausea & Other Causes
Tummy Troubles? Get a better idea of what's causing the nausea, vomiting, bloating, gas, constipation, diarrhea, pain, and other...
Worst Foods for Digestion
Discover which foods to avoid in order to prevent diarrhea and digestive problems. Find out which foods can trigger diarrhea and...
Causes of Gas
Abdominal Adhesions (Scar Tissue)
Abdominal adhesions (scar tissue) bands of scar tissue that form between abdominal organs and tissues. Symptoms of abdominal...
Amebiasis (Entamoeba histolytica Infection)
Amebiasis is an infection caused by an amoeba. Signs and symptoms include bloody stools, abdominal pain, weight loss, fever, and...
Bile Duct Cancer (Cholangiocarcinoma)
Bile duct cancer (cholangiocarcinoma) is a rare type of cancer that arises from cells that line the drainage system from the...
Celiac disease is a condition in which a person has inflammation of the small intestinal mucosa when exposed to gluten in the...
Cyclospora Infection (Cyclosporiasis)
Cyclospora cayetanensis is a parasite that causes infection when humans ingest food contaminated with feces from an infected...
Exocrine Pancreatic Insufficiency (EPI)
Exocrine pancreatic insufficiency or EPI is a condition in which a person's pancreas can't produce or secrete certain enzymes...
Gastroparesis is a medical condition in which the muscle of the stomach is paralyzed by a disease of either the stomach muscle...
Heartburn is a burning sensation experienced from acid reflux (GERD). Symptoms of heartburn include chest pain, burning in the...
IBS Triggers (Prevention)
Irritable bowel syndrome (IBS) is a functional disease that can affect the quality of those who suffer from this condition....
Indigestion (Dyspepsia, Upset Stomach Pain) Symptoms, Relief Remedies, Medicine
Indigestion (dyspepsia) can be caused by diseases or conditions that involve the gastrointestinal (GI) tract, and also by some...
Intestinal Gas (Belching, Bloating, Flatulence)
Anal itching is the irritation of the skin at the exit of the rectum, known as the anus, accompanied by the desire to scratch....
Irritable Bowel Syndrome (IBS)
Irritable bowel syndrome (IBS) is a GI (gastrointestinal) disorder with signs and symptoms that include abdominal pain, bloating,...
Lactose intolerance is a common problem where a person's digestive system cannot digest lactose. Signs and symptoms include:...
Peritonitis is a bacterial infection inside of the abdomen. Some doctors choose to group the causes of peritonitis into five...
Sick Building Syndrome
Multiple chemical sensitivity (MCS) or also referred to as sick building syndrome or environmental illness is the name given by...
Other Causes of Gas
- Dietary Fat, Starchy Grains
- Digestive Disease
- Intestinal Blockage
- Pancreatic Insufficiency
Examples of Medications for Gas
Subscribe to MedicineNet's General Health Newsletter