Farts that smell like rotten eggs? Why you might be passing sulfuric gasses, according to gut-health

October 2024 · 7 minute read
This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.  Medically Reviewed Reviewed By Check Mark Icon A check mark. It indicates that the relevant content has been reviewed and verified by an expert Our stories are reviewed by medical professionals to ensure you get the most accurate and useful information about your health and wellness. For more information, visit our medical review board.

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Everybody passes gas — in fact, most people fart between 5 and 15 times each day. And though sometimes you might be able to get away with fairly odorless flatulence, it's not unusual for the occasional bad-smelling fart to slip out.

While it's embarrassing to rip a fart that smells like rotten eggs on a subway or elevator, that awkward next few minutes may not be your only concern. 

Your egg and steak breakfast burrito could be the only thing to blame, but those foul toots could also be a sign of a more serious underlying condition. Here's how to tell. 

2. Sulfur-rich foods

"Foods high in sulfur, such as dairy, eggs, meat, and some vegetables such as cauliflower, can produce the 'rotten egg' smell," says Dr. Kenneth Josovitz, a gastroenterologist with Gastro Health.

This is due to a compound the foods contain called hydrogen sulfide. As the bacteria in your gut break down these foods, they release sulfur gas which smells like rotten eggs. 

This isn't a sign that your body has an intolerance for these foods, it's just part of normal digestion. 

Foods that are rich in sulfur include:

What to do about it: Avoid the foods at times that gas might be particularly embarrassing, like on a date. Swap high-sulfur foods for ones that have less sulfur, like spinach, zucchini, bell peppers, grains and fish. When you can't avoid sulfur-rich foods, take an over-the-counter alpha-galactosidase gas reducer like Beano before you eat. This will help break down the sulfur-rich foods without as much gas. 

3. Lots of fiber

Soluble fiber is like a traffic jam for your digestive tract: it slows down how fast waste moves through you. Extra time in the digestive tract means that your gut bacteria have longer to break the waste down and release more gas, Josovitz says.

This gas may also contain sulfuric compounds, since "foods that are high in fiber are often simultaneously high in sulfur," says Trista K. Best, a registered dietician with Balance One. 

Some foods high in soluble fiber include:

People who eat a plant-based diet might be at higher risk for farts that smell like rotten eggs because they tend to have higher fiber intake, Best says. 

What to do about it: First off, don't skip fiber-rich foods. "It can be difficult and unwise to completely remove these foods from your diet," Best says. "They are some of the most nutrient dense foods available and avoiding them could cause health issues."

Instead, take steps to process fiber without farts. Stay hydrated, and avoid behaviors like chewing gum that can cause you to swallow air and compound gas. Consider taking an over-the-counter alpha-galactosidase gas reducer like Beano. If taken before you eat, this medicine will help you break down fiber without excessive gas.

3. Unbalanced gut microbiome

Your body has a natural population of bacteria, but sometimes bacteria overgrow or the balance is thrown off. Having an unbalanced gut bacteria is called gut dysbiosis. The following factors can contribute to gut dysbiosis:

Note: A major cause of gut dysbiosis is taking antibiotics, which can kill off the good bacteria in your gut.  Only use antibiotics for serious conditions. 

If the bacteria in your gut are unbalanced, you might have more of the bacteria that releases hydrogen sulfide. This can cause more sulfurous farts. 

If you have gut dysbiosis, you'll likely notice other symptoms, Best says, including:

What to do about it: Talk to your doctor about what's causing your gut dysbiosis. Probiotics introduce healthy bacteria into your gut and can help combat gut dysbiosis. 

Prebiotics, which feed gut bacteria, can also help. And if you have a gut infection, you might need antibiotics to control the growth of harmful bacteria. 

4. Food intolerances

If you have a food intolerance like lactose intolerance, your gut is unable to digest certain foods. 

Instead, those foods linger in your gut where they ferment, Josovitz says. That process causes them to release gas, which may smell like rotten eggs. 

If you have food intolerance, you'll notice smelly farts up to 48 hours after eating the food you're intolerant of. You may also notice symptoms including:

What to do about it: See a doctor and discuss how to find out which foods you're intolerant to. Keeping a food journal can help you identify which foods make you gassy. If that doesn't give clear answers, an elimination diet might help you pinpoint which foods cause gas for you. This can help you avoid these foods in the future. Finally, talk to your doctor about an allergy test, which might reveal which foods you're allergic to, although it won't reveal all your food intolerances. 

5. Constipation

Constipation, or having less than three bowel movements each week, leads to stool and waste building up in your gut, which can cause excess, foul-smelling gas as it breaks down, Josovitz says. 

If you're constipated, you'll likely notice other symptoms including:

What to do about it: Treat constipation by drinking more water and eating more fiber. If you experience ongoing constipation, talk to your doctor about whether medication including over-the-counter laxatives or prescription laxatives are right for you. 

When to see a doctor

While farting is normal, you should see a doctor if you have particularly smelly farts. 

"It is not normal to consistently have foul smelling gas," Best says. "If you review your diet and have no reason to believe your gas is related to the foods you eat, then medical attention may be necessary to rule out more serious causes."

You should also see a doctor if you have:

In rare cases, having farts that smell like rotten eggs can be a sign of serious conditions, Josovitz says, including:

Your doctor may order X-rays, blood tests or stool tests to diagnose these conditions. Treatment for excess gas involves dietary changes to eliminate the foods that cause you trouble. 

Insider's Takeaway

Although having odorous gas might be awkward, they're not usually cause for concern. 

"Smelly farts are a normal byproduct of digestion, and usually are not worrisome," Josovitz says. 

Usually, adjusting your diet to avoid sulfur-rich foods like cabbage or Brussels sprouts is enough to get rid of your stinky farts. If not, keeping a food journal can help you identify what foods are the culprit. 

But if that doesn't solve the issue and your stinky farts stay, talk to your doctor. 

"After evaluating your diet for non-serious causes of foul smelling gas you should seek medical attention," Best says. 

Kelly Burch Kelly Burch is a New Hampshire-based freelance journalist writing about finances, health, family, and more. Her work has appeared in The Washington Post, The Chicago Tribune, and Forbes, among others. Follow her on Facebook or Twitter, and or learn more here.    Read more Read less

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