P.U.! What's that smell? How can your body make something so stinky?

Farts — also called flatus (say: flay-tus) or intestinal (say: in-tes-tuh-null) gas — are made of, well, gas!

When you eat, you don't swallow just your food. You also swallow air, which contains gases like nitrogen (say: ny-truh-jen) and oxygen (say: ahk-sih-jen). Small amounts of these gases travel through your digestive system as you digest your food. Other gases like hydrogen (say: hy-droh-jen), carbon dioxide (say: kar-bon dy-ahk-side, the gas that makes soda fizzy), and methane (say: meth-ain) are made when food is broken down in the large intestine. All of these gases in the digestive system have to escape somehow, so they come out as farts!

Gases are also what can make farts smell bad. Tiny amounts of hydrogen, carbon dioxide, and methane combine with hydrogen sulfide (say: suhl-fide) and ammonia (say: uh-mow-nyuh) in the large intestine to give gas its smell. Phew!

All people fart sometimes, whether they live in France, the Fiji islands, or Fresno, California! If you have a dog, you may have even been unlucky enough to have heard (or smelled) Fido farting. Intestinal gas is totally normal, and it's very rare for farting to be a sign that something is wrong in the body.

If you want to be less farty, try cutting back on foods like beans, onions, and fried foods. These can release larger amounts of gas as they break down in your body. If you have a lot of gas after you eat ice cream, yogurt, or milk, talk to your parent about it — your body may have a difficult time digesting the natural sugar called lactose, which is found in dairy foods. And don't forget that farting can sometimes be your body's sign that it's time to take a trip to the bathroom.

The bathroom is also a good place to go if you're feeling particularly gassy because it's not polite to fart in social settings, like in class or at the dinner table (yuck!). But don't worry if this happens accidentally. Just remember to say "excuse me"!

Reviewed by: Steven Dowshen, MD
Date reviewed: July 2009

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