Flatulence, which is sometimes called passing wind, passing gas, or farting, is a biological process that helps to release gas from digestion.

In some cases, they’re silent and odorless, but farts can become uncomfortable when they’re loud and foul-smelling.

Smelly gas is not uncommon and is often considered normal. Some foods or medications can cause excessively smelly farts.

There are, however, some instances when smelly farts can be an indicator of an underlying infection, digestive issues, or a disorder.

There are a number of reasons why your farts may smell bad. In most cases, foul-smelling flatulence is associated with the foods you eat and an unbalanced diet.

However, there can be more serious causes of rotten-smelling gas.

1. High fiber foods

Many high fiber foods can cause you to pass more gas. It takes longer for these foods to break down in your digestive system, so they ferment over time.

High fiber foods also sometimes smell, which means your farts may smell, too. This is especially true with strong-smelling vegetables, such as:

Your gas may smell like rotten eggs because of the sulfur in fiber-rich foods. Sulfur is a natural compound that smells like spoiled eggs. Many vegetables are sulfur-based.

If this is causing your flatulence, simply modifying your diet could be enough to reduce it.

2. Food intolerance

If you have a sensitivity or reaction to certain foods, your gas could have a foul odor. For example, people with lactose intolerance can’t break down the sugar lactose. As a result, it’s fermented by bacteria in the gut.

Gluten-related disorders, including celiac disease, can also cause smelly farts. Celiac disease is an autoimmune disease where there is an immune response to the protein gluten. This leads to inflammation and injury in the intestine, leading to malabsorption and flatulence.

Other than bad-smelling flatulence, celiac disease can cause other symptoms:

Talk with your doctor to get tests and determine whether you have any food allergies or sensitivities that may be making your farts smell.

3. Medication

Although uncommon, certain medications can cause smelly flatulence.

Antibiotics kill off harmful pathogens in the body, but they can also destroy some of the “good” bacteria in your stomach, which aids digestion. Without this bacteria, your gas may smell. You could also experience bloating and constipation.

Treatment for this cause involves changing medication, which you should only do under the direction of a healthcare professional.

4. Constipation

Constipation indicates that you have a buildup of stool, or poop, in your colon. If you can’t poop regularly, it can cause bacteria and odor to develop. The end result is foul-smelling and sometimes painful gas.

Taking over-the-counter laxatives can be a simple home remedy for constipation.

5. Bacteria buildup and digestive tract infections

When your body digests food, it extracts nutrients and sends them to the bloodstream. The waste products are sent to the colon. Disrupting the digestion process can cause an overgrowth of bacteria.

Some bacteria can cause infection in the intestines and digestive tract. This may cause a higher volume of gas than normal and a strong-smelling odor. People with digestive tract infections also often have abdominal pain and diarrhea.

Visit your doctor to determine you have a bacterial infection. If you do, they’ll prescribe antibiotics to clear the infection and get you feeling better.

6. Colon cancer

A more rare cause of smelly farts is colon cancer. When polyps or tumors form in the digestive tract, it can cause a partial bowel obstruction, which results in gas buildup and bloating.

If you begin to experience abnormal smelling gas and discomfort, and a change in diet or medication doesn’t affect your symptoms, call your doctor for full evaluation. They can determine whether a colonoscopy is warranted.

Treatment for colon cancer varies based on the stage of cancer. It can include surgery to remove tumors and chemotherapy to kill cancer cells.

In most cases, having foul or odorless flatulence is no cause for alarm.

However, if your gas is accompanied by irregular symptoms, you should visit a doctor immediately. Some adverse symptoms you may experience alongside smelly gas include:

Flatulence is natural and necessary to dispose of waste and gas in the body. Some things you can do to reduce the chance of smelly farts include:

  • eating smaller portions at a slower pace to encourage healthy digestion and reduce gas production
  • drinking more water to help move waste through the body more efficiently
  • including probiotic foods like yogurt in your diet to help restore healthy bacteria in your body and improve digestion
  • avoiding carbonated drinks that can produce gas, including beer, sparkling wine, and soda
  • avoiding foods that contribute to smelly gas

Why do my farts smell so bad?

Foul-smelling gas usually has a simple cause, like high fiber foods or certain medications. However, it could be an indicator of underlying digestive issues or even colon cancer, so be sure to contact a doctor if your symptoms are concerning you.

Are smelly farts a sign of an unhealthy body?

Smelly farts don’t necessarily mean that your body isn’t in good health. In fact, farting is often a sign of a healthy digestive system, and many people experience strongly-odored flatulence.

However, if your gas is accompanied by other unpleasant symptoms or pain that seems out of character for you or excessive, you should speak to a doctor.

Why do some farts smell worse than others?

Only 1 percent of the gas humans release actually smells bad. The cause of the odor is intestinal bacteria that produce compounds containing sulfur. Most farts are caused by swallowed air or healthy gut bacteria that release gas after breaking down food.

Because most of our gas is odorless and smelly gas can be caused by various factors, some farts are bound to smell worse than others.

How often should a healthy person fart?

An average person in good health typically passes gas 12 to 25 times per day. People tend to fart the most during sleep because the amount of gas in your intestines increases throughout the day.