• Digestive Disorders
• Infections
• Constipation

Why Do My Farts Smell So Bad? 7 Causes of Smelly Gas

Everyone experiences foul-smelling gas at some point, but when it becomes a regular occurrence, you might find yourself embarrassed and concerned.

There are several reasons why your gas might have a particularly strong odor, ranging from your individual gut flora to infection and illness.

In this article, we’ll explore the most common causes behind smelly farts and what you can do to manage them.

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Is it Normal to Have Foul Smelling Gas?

It’s quite normal for the body to produce foul-smelling farts from time to time. 

The odor is often caused by the breakdown of certain foods in the digestive system and the production of gasses like hydrogen sulfide, which can smell like rotten eggs.

While occasional foul-smelling farts are normal, persistently bad-smelling gas may indicate dietary issues or digestive problems.

7 Causes of Smelly Flatulence

Here are some of the most common reasons why you may be experiencing persistently foul-smelling gas:

Gut flora

Your gut flora — the community of bacteria living in your intestines — plays a significant role in digestion and can affect the odor of your gas. 

These bacteria help to break down food and produce various gasses, some of which smell unpleasant.

When you consume fiber-rich foods, certain complex carbohydrates reach the large intestine undigested. Your gut bacteria ferment these carbohydrates, producing gas such as methane, hydrogen, and carbon dioxide. 

Some bacteria also produce sulfur-containing compounds, like hydrogen sulfide. These gasses have strong odors and can make farts particularly smelly.

Medications

Certain medications, like antibiotics, laxatives, diabetes medicine, and cholesterol-lowering drugs, can cause foul-smelling gas due to their effects on digestion, gut flora, and the absorption of nutrients.

Here’s how medications can cause smelly gas:

• Alteration of the gut flora: Medications can disrupt the balance of gut bacteria by killing both harmful and beneficial bacteria. As a result, gas-producing bacteria may overgrow, releasing foul-smelling sulfur compounds. This imbalance increases food fermentation in the intestines, leading to more gas and a stronger smell.

• Impact on digestion: Certain medicines affect how food is digested and absorbed, leading to incomplete digestion. This leaves more food residues for gut bacteria to ferment, allowing them to break down food more thoroughly, increasing gas and odor production.

• Delayed gastric emptying: Some medications slow down the movement of food through the digestive system, allowing for extended fermentation. This can cause increased gas production and foul-smelling farts.

Constipation

When you’re constipated, food waste and stool remain in the colon for a longer period than usual. The additional time gives bacteria more opportunity to break down undigested food particles in the intestines.

The longer the bacteria ferment this food, the more gasses are produced, some of which have a very strong, unpleasant odor.

When stool sits in the colon for an extended period, it can become more compact and dry. The accumulation of waste can lead to the production of gasses that are more concentrated and smellier as a result.

Infection or illness

Infections and illnesses can cause foul-smelling gas because they disrupt the normal balance of gut bacteria, affecting digestion and causing inflammation in the gastrointestinal tract.

The following conditions can all contribute to particularly foul-smelling farts:

• Gastroenteritis: Caused by bacterial or viral infections, stomach flu can alter the composition of gut flora, leading to an overgrowth of gas-producing bacteria. The antibiotics used to treat this type of infection can kill both beneficial and harmful bacteria, resulting in an imbalance in the gut that can increase the production of foul-smelling gas.

• Small intestinal bacterial overgrowth (SIBO): This is a condition in which excess bacteria in the small intestine ferment food faster than usual, leading to excessive gas production and foul flatulence.

• Inflammatory conditions: Conditions like Crohn's disease, ulcerative colitis (UC), and irritable bowel syndrome (IBS) cause inflammation and irritation in the digestive tract. The inflammation can affect how food is digested and absorbed, allowing gut bacteria to ferment undigested food. The result is increased gas production, often accompanied by stronger, more unpleasant odors.

• Food intolerances: With lactose intolerance, the body lacks the enzyme lactase, which is needed to break down lactose, a sugar found in dairy products. When lactose remains undigested, it’s fermented by the gut bacteria in the colon, leading to the production of gasses like hydrogen, methane, and sulfur compounds, which can be quite smelly.

• Celiac disease (CD): Celiac disease causes an immune reaction to gluten, leading to inflammation and damage in the small intestine. This damage impairs nutrient absorption, allowing undigested food to reach the colon, where it is fermented by bacteria, resulting in bad-smelling farts.

Menstruation

Getting your period can cause foul-smelling gas due to hormonal changes and altered movement in the gut.

In the days before and during menstruation, progesterone levels fluctuate. High levels of progesterone can relax the smooth muscles throughout the body, including those in the digestive tract. 

This relaxation may slow the rate at which food moves through the gut, leading to delayed digestion and longer fermentation time for food in the intestines. 

The longer food sits in the gut, the more time bacteria have to break it down, resulting in more gas and, potentially, a more pungent odor.

Changes in estrogen levels can also alter how the gastrointestinal system functions, leading to bloating, gas, and changes in stool consistency.

Eating certain foods

Even eating healthy foods can cause foul-smelling flatulence. Here are some gas-producing foods you should know about:

• Eggs: Naturally rich in sulfur, eggs can produce hydrogen sulfide gas during digestion.

• Meat: Red meat, in particular, is high in sulfur-containing amino acids. When gut bacteria break down these proteins, they produce sulfur-containing gases.

• Cruciferous vegetables: Vegetables like broccoli, cauliflower, cabbage, Brussels sprouts, and kale are also high in sulfur.

• Beans and legumes: Beans, lentils, chickpeas, and peas contain complex carbohydrates and fiber that aren’t fully digested in the small intestine. When they reach the large intestine, they are fermented by gut bacteria, producing gas.

• Whole grains: Foods like oats, barley, and bran are high in fiber, which can increase gas production and strong-smelling farts.

• Lactose-containing foods: Milk, cheese, yogurt, and ice cream all contain lactose. As mentioned earlier, this is a sugar that some people can’t fully digest.

• Fruits high in sorbitol: Apples, pears, peaches, and prunes contain sorbitol, a natural sugar alcohol that can cause gas when fermented by gut bacteria.

• Fruits high in fructose: Fruits like mangoes and watermelon are high in fructose, a sugar that can cause gas if not properly absorbed by the small intestine. 

What Can I Do About Bad-Smelling Flatulence?

There are some things you can do to potentially reduce the odor of your farts, including:

Making changes to your diet

The first step is to find out which foods are causing your smelling farts. Keep a food diary or use an app to identify which foods trigger your symptoms and try reducing your intake or avoiding them.

While high-fiber foods are essential for digestion and overall well-being, increasing them too quickly can lead to gas. 

Try moderating your intake of fiber-rich foods to see if it helps reduce the odor of gas.

Eating slowly

Eating quickly can cause you to swallow air, which can contribute to gas. Chewing your food slowly and thoroughly aids digestion and minimizes the amount of air swallowed, which can help reduce gas production.

Staying hydrated

Drinking plenty of water helps your digestive system process food more effectively, reducing the likelihood of intestinal gas buildup and odor.

Taking probiotics

Probiotics can help balance the bacteria in your gut, improving digestion and potentially reducing gas odor. Yogurt, kefir, fermented foods, and probiotic supplements can all support healthy gut flora.

Taking over-the-counter (OTC) remedies

There are some OTC medications you can use to reduce foul-smelling farts, including:

• Activated charcoal: Some people find that activated charcoal helps reduce gas odor by absorbing it in the digestive tract.

• Digestive enzyme supplements: Products like Beano contain enzymes that help break down complex carbohydrates found in foods like beans and vegetables, reducing gas production.

• Simethicone: Simethicone-based products, like Gas-X, can help reduce gas and bloating, though they may not specifically target odor.

Avoiding artificial sweeteners

Sugar alcohols like sorbitol and xylitol, which are often found in sugar-free candies and chewing gum, can cause gas and bloating. Cutting back on products containing these sweeteners may help to reduce stinky farts.

Where Can I Learn More About My Digestive Health?

Through LifeMD, you can consult with our board-certified physicians and nurse practitioners to discuss your digestive health and get treatment for symptoms you may be experiencing.

We can connect you with a team of healthcare professionals who can order lab work and provide medical advice and treatments for various conditions.

Make your online appointment today.

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