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Why Does My Poop Smell like Burnt Hair?

author avatar Dr. Eric Berg 08/31/2023

Poop that smells of burnt hair, rubber, iron, or chemicals can indicate potential issues with your digestive system. 

While an unpleasant odor often is harmless and may be linked to the foods you're eating, smelly poop can also be caused by bacterial infection, celiac disease, internal bleeding, and inflammatory bowel disease.   

Discover some common reasons for foul-smelling stools and why it’s a good idea to monitor your poop.  

Woman on the toilet with foul-smelling poop

What the smell of your poop says about your health

The color, consistency, and smell of your stools can provide important information about the health of your digestive tract. 

Poop contains a range of volatile organic compounds (VOC), which are metabolic and microbial by-products such as methane, benzaldehyde, acetone, and sulfur gas that emit pungent smells, giving stool its distinct odor. 

The composition and concentrations of VOCs can provide valuable insight into your metabolic and digestive health. 

Different levels of VOCs have been found to indicate potential health issues, including irritable bowel syndrome, Crohn’s disease, or intestinal infection.  

In fact, research published in the World Journal of Gastroenterology suggests, “Patterns of fecal VOCs, and thus patterns of smell, can be used to identify disease states.”

Here are six common poop smells and their potential causes. 

1. Burnt hair

Stool with a foul odor reminiscent of burnt hair is typically linked to sulfur-containing VOCs.

Consuming sulfur-containing foods such as garlic, onions, and cruciferous vegetables can raise concentrations of sulfur gas in the digestive tract, causing burnt hair poop smell. 

Burnt-match fecal odors are also common after consuming large amounts of sulfur-rich foods or may be caused by prescription drugs, including antibiotics, diuretics, and diabetes medications. 

There also is evidence that malabsorption has been linked to poop that smells like burnt hair. 

Digestive conditions such as celiac disease or irritable bowel syndrome can impair digestive function and prevent your body from absorbing nutrients.

When undigested food enters the large bowel, it’s degraded and fermented by intestinal microbes, which releases a range of different VOCs and may explain why malabsorption syndrome is associated with a foul stool smell.    

2. Burnt rubber or chemicals

Poop with an acrid and chemical smell can be caused by antibiotic drugs that can alter the composition of gut bacteria, also known as dysbiosis, linked to changes in fecal smell.

Mercaptans are a type of VOC often described as having a burnt rubber smell. 

Dysbiosis and parasitic infections such as Giardia have been linked to higher concentrations of mercaptans in stool and may be the reason for poop that smells of sulfur or burnt tires.

Burnt popcorn

3. Burnt popcorn 

Stool and urine that smells like burnt popcorn can be a side effect of uncontrolled diabetes or prescription drugs.  

Research published in Diabetes Care found that metformin, a popular anti-diabetic medication promotes the elimination of excess blood sugar through the stool rather than urine.  

When sugar enters the colon, it causes bacterial fermentation, which can liberate VOCs with a sweet, almost popcorn-like smell. 

Depending on the unique composition of the microflora, higher concentrations of sulfur gas may be generated, which can result in a stool smell similar to burnt popcorn. 


4. Iron

Iron has a unique smell, and eating iron-rich foods or taking iron supplements can make your poop smell metallic or even blood-like. 

Stools that smell of iron can also be a sign of gastrointestinal bleeding, which can be caused by various factors, including Crohn's disease, intestinal ulcers, hemorrhoids, or inflammatory bowel disease. 

5. Coffee

Certain foods can change the odor of your stool.

Coffee contains various compounds, including volatile oils and other aromatic substances, that can undergo chemical changes during digestion and may produce a coffee-like odor in your stool.

If you consume too many chocolate-covered coffee beans, it’s possible that your stool can have a coffee bean odor.

Dark roast coffee may also produce a burnt coffee smell.

3. Ammonia

Ammonia is a byproduct of protein metabolism that’s eliminated via the kidneys.

If your stool smells strongly of ammonia, you may be dehydrated, consume too much protein, or have certain liver and kidney conditions. 

Magnifying glass

The importance of monitoring your poop

Poop isn’t just a waste material. It can provide valuable insight into your overall health.

While some day-to-day variations in stool smell can be expected, unusual changes in odor, color, consistency, or frequency may indicate potential health problems. 

In fact, research published in Healthcare suggests, “Self-appraisal of stool frequency and consistency may be a simple but useful tool for informing about major chronic illnesses.”

Stools that contain blood may be a sign of conditions like hemorrhoids, intestinal inflammation, ulcers, or colorectal cancer. 

Your poop also reflects your dietary habits and can highlight if your body isn’t absorbing nutrients well, you have a food allergy, or your digestive process is sluggish. 


Pale-colored stool typically results from sluggish gallbladder function and fat malabsorption, and poop that’s small and hard can be a sign of dehydration or lack of dietary fiber.   

Woman holding stool test

When to see a doctor

A sudden and significant change in the smell of your poop without any apparent reason may be a sign of an underlying health issue.

It’s recommended to consult a medical professional if you experience:

  • Prolonged foul-smelling stool

  • Blood in your stool 

  • Stools that are abnormal in color or texture 

  • Sudden changes in bowel movements 

  • Persistent gastrointestinal issues  

  • Abdominal pain 

A thorough evaluation of your symptoms in combination with blood tests and laboratory assessment of your stool can identify potential causes and help to formulate an individual treatment plan.  

Digestive system illustration

Key takeaways

Your poop says a lot about your health. 

While most cases of foul-smelling stools reflect your diet, hydration status, and medication use, they also can be a symptom of underlying health issues. 

If you experience sudden and noticeable changes in the odor, color, or consistency of your poop, it’s essential to consult a healthcare provider to rule out gastrointestinal bleeding, inflammatory disorders, and malabsorption.


1. Why does my poop smell like burnt matches?

Poop that smells like burnt matches is typically a result of higher concentrations of sulfur gasses in the large intestines. 

Microbes residing in the large bowel ferment organic matter, which releases a wide range of odorous compounds, including sulfur, which has a pungent odor often described as burnt matches, natural gas, or rotten eggs. 

2. Why does my poop smell like burning sulfur?

There is evidence that sulfur-rich foods, malabsorption syndrome, and drugs such as antibiotics, diuretics, and diabetes medications can increase sulfur production in the large intestines, resulting in stools that smell like burning sulfur. 

3. Why does my poop smell like burnt hair?

Poop that smells of burnt hair can be a result of sulfur-rich foods such as onion, garlic, and cruciferous vegetables. 

In addition, malabsorption also has been linked to stool odor reminiscent of burnt hair. Undigested food is degraded and fermented by intestinal bacteria, which generate several different gasses with pungent odors. 

4. What does it mean when my poop smells like iron?

Stool that smells of iron can be indicative of intestinal bleeding, hemorrhoids, or ulcers. Blood contains iron which has a distinct metallic smell when exposed to oxygen.

It’s important to consult with a medical professional if your poop smells of iron or if you notice sudden changes in the color of your stools.  

5. Does celiac poop smell bad?

People with Celiac disease often have some degree of dysbiosis, also known as an imbalanced intestinal microflora, linked to higher concentrations of pungent volatile organic compounds (VOCs) in the large bowels. 

In addition, even small amounts of gluten can trigger bouts of diarrhea and foul-smelling poop. 

6. Why does my poop smell weird all of a sudden?

Sudden changes in stool odor can reflect dietary choices or medication use. However, smelly poop can also be indicative of potential underlying health issues such as intestinal infection, bleeding, or malabsorption. Make sure you closely monitor your stool if it suddenly has a different smell.

7. Why does my poop smell metallic?

Poop that smells metallic typically contains iron which can be caused by iron supplements or may indicate intestinal bleeding, hemorrhoids, or ulcers. 

8. What does Giardia smell like?

Giardia infections have been linked to poop that has a distinctive foul smell often described as sulfuric or rotten egg-like. Smelly poop along with abdominal cramping and pain could indicate an infection.

9. Why do I keep smelling ammonia?

Ammonia odor in poop can be a sign of dehydration, a high protein diet, or poor kidney function. 

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