Why Your Farts Smell (2024)

By the time you finish reading this article, it’s possible you unknowingly passed gas. Seriously, it’s true. The average person lets some air escape from their nether regions more than 20 times a day.

Now, 99% of those poofs draw no attention. They’re not loud. They’re not stinky. They’re not toast-your-buns hot.

But then there’s that other 1%. The farts that can clear out rooms.

So, why does some flatulence smell sooooo bad? And are odiferous toots a sign that something troublesome is brewing deep inside of you? For answers, we turn to gastroenterologist Christine Lee, MD.

What causes farts?

To understand why farts smell, it helps to know their origin story. Intestinal gas typically forms one of two ways, says Dr. Lee.

• Food digestion. Everything that you gobble and gulp ends up in your gut, where it’s broken down while being digested. This process creates hydrogen, carbon dioxide, methane and other gases that fuel flatulence.
• Swallowing air. The average person swallows about 2 quarts of air a day while chewing, talking, snoring and drinking. Most of that comes back up in burps. Some, though, travels down through your intestine before slipping out of your lower orifice.

Why do some farts smell?

Let’s start with the #1 reason for stinky farts: It’s tied to something you consumed.

Gasses that form during your digestive process can be a healthy result of a nutritious diet loaded with fiber-rich foods. Digestion sometimes churns up hydrogen sulfide, which can add a rotten-egg odor to any air biscuit you cook up.

“As people often say, what goes in comes out,” notes Dr. Lee. “That’s a good way to think of what’s behind most foul gas.”

Foods that cause stinky farts

Certain healthy menu items may reintroduce themselves in an unpleasant vapor form hours after your meal. The list includes:

Beans

There’s a reason beans earned a label as “the musical fruit.” Many beans are chock full of carbohydrates and sugars that don’t digest easily. Breaking down this fiber-rich food can lead to fermentation and a gas buildup in your gut. A loud and stinky result often follows.

Cruciferous vegetables

Let’s get realistic: Cooking broccoli on the stovetop gives off a whiff of unpleasantness tied to a high sulfur content. When that food rolls through your digestive system … well, it only raises the stench level, says Dr. Lee.

Broccoli’s cruciferous cousins — Brussels sprouts, cauliflower and cabbage, to name a few — bring similar results.

Other high-sulfur foods

The following foods contain enough sulfites to draw notice by adding a certain zest to farts:

• Alcohol such as beer and wine.
• Eggs.
• Garlic.
• Grains.
• Meats.
• Nuts.
• Onions.

Protein powders used by athletes or people looking to drop pounds may also cause some eye-burning flatulence. Blame the use of cysteine, a sulfur-containing amino acid that’s often in whey powder.

Dairy products

An intolerance or sensitivity to lactose can create digestive distress and some pretty pungent farts, says Dr. Lee. Consider it the backstory behind the phrase “cutting the cheese” to describe bad gas. (Many kinds of cheese, by the way, have high sulfur content.)

Sugar alcohols and artificial sweeteners

Your body can’t fully absorb many low-calorie sweeteners in diet products, which leaves them sitting in your gut. The resulting gas can be rather rancid.

Spicy foods

Ever have a fart that just feels warmer than normal? Odds are it’s because of some spicy food you ate earlier. Basically, the fiery substances that burn your tongue do the same to your bottom while blasting out.

Medical reasons for smelly farts

Food may be the main reason for smelly gas, but it’s not the only one. Other sources include:

Gut flora

It’s possible the cause of your stinky farts is just … well, you. The chemistry is different in everyone’s gut, Dr. Lee explains. Yours may just have bacteria that naturally leads to gas that smells a bit stronger.

Medications

Taking medications — especially antibiotics — can throw your digestive system into temporary turmoil and even lead to a C. diff infection, notes Dr. Lee. The resulting imbalance can lead to some foul-smelling farts.

Constipation

A backlog of poop in the chute doesn’t exactly help with fart odor.

Infections or illness

Foul-smelling farts usually come and go. If that stench keeps coming, though, it may be a sign that something isn’t quite right inside. Conditions that could cause smelly farts include:

• Inflammatory bowel disease (IBS), including disorders such as Crohn’s disease and ulcerative colitis.
• Colorectal cancer.
• A small bowel or large bowel obstruction.
• A bacterial infection or overgrowth.

If bad gas continues for an extended period, talk to your healthcare provider to find a cause.

How do you make stinky farts go away?

The problem usually takes care of itself if it’s linked to what you ate or medication, says Dr. Lee. The symptoms should disappear once the offending item works through your system. (Provided there isn’t continued usage, of course.)

Over-the-counter digestive aids and regular exercise may help cut down on farts. Changing your diet and avoiding offending foods should also take the wind out of those sails.

On the whole, though, Dr. Lee says passing gas is just part of a regular organic process. But if it’s excessive or smells particularly foul, get checked by your healthcare provider to see if it’s a medical issue.