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What Causes Foul-Smelling Stools?

Foul-Smelling Stool

Feces normally have an unpleasant smell, but it is a smell that is common and unremarkable. Foul-smelling stools have an unusually strong, putrid smell. Although in many cases, foul-smelling stools are related to the foods you eat, and the bacteria flora resident in your colon they can also indicate a serious health problem. Diarrhea, bloating, or gas (flatulence) may accompany foul-smelling stools. These stools are often soft or runny and are not considered a regular bowel movement.

What Causes Foul-Smelling Stool?

Often a change in your diet is the reason for foul-smelling stools; malabsorption is another common cause. Malabsorption occurs when your body is unable to absorb the proper amount of nutrients from the food you eat. This generally occurs when there is an intestinal infection or an intestinal disease that prevents your intestines from absorbing nutrients from your food.

Common causes of malabsorption are:

  • Celiac disease—a reaction to gluten damages to the lining of the small intestine that prevents proper absorption of nutrients
  • inflammatory bowel disease—Crohn’s or colitis, for example
  • carbohydrate intolerance–the inability to completely process carbohydrates (sugars and starches)
  • Dairy protein and other food allergies

A common symptom of malabsorption is foul-smelling diarrhea

If you have inflammatory bowel disease, also known as IBD, eating certain foods will cause your intestines to become inflamed. People with IBD often complain of foul-smelling diarrhea or constipation. Affected individuals also have flatulence after eating certain foods. This flatulence may have a foul smell.

Infections that affect the intestines may also cause foul-smelling stools. One infection called gastroenteritis occurs after ingesting food that has been contaminated with E. coli and Salmonella, as well as certain other viruses, bacteria, or parasites. Soon after developing the infection, you may experience abdominal cramps and then have foul-smelling, runny stools.

Certain medications may cause gastrointestinal discomfort and diarrhea. Taking some over-the-counter multivitamins may also cause foul-smelling stools if you’re allergic to the supplements’ ingredients. After a course of antibiotics you may experience foul smelling stools until your normal bacterial flora is restored.

Foul-smelling diarrhea can be a side effect of taking more than the recommended daily allowance of multivitamins or of any single vitamin or mineral. Diarrhea associated with a multivitamin or medication overdose is the sign of a medical emergency. Getting too much vitamin A, D, E, or K can have life-threatening side effects.

Other conditions that can cause foul-smelling stools include chronic pancreatitis, cystic fibrosis, and short bowel syndrome (surgical removal of part of the small intestine inhibits absorption of nutrients).

Signs of Foul-Smelling Stool

Symptoms that may be associated with foul-smelling stools include:

  • runny stool (diarrhea)
  • soft stool
  • frequent bowel movements
  • abdominal pain
  • nausea
  • vomiting
  • flatulence
  • abdominal bloating

Foul-smelling stools may be the sign of a serious medical condition. See your doctor immediately if you develop any of the following symptoms:

  • blood in your stool
  • black stool
  • pale stool
  • fever
  • abdominal pain
  • unintentional weight loss
  • chills

How Is Foul-Smelling Stool Diagnosed?

During your visit with your doctor, he or she will ask questions about your feces, including its consistency and when you first noticed the foul odor. If the consistency of your stools has recently changed, your doctor will want to know when the change occurred. He or she will also ask if you’ve made any dietary changes. Tell your doctor about any foods you ate before your stools became foul-smelling but have stopped eating, as well as foods you’ve recently begun to eat.

At this point, your doctor may ask for a stool sample to check for bacterial, viral, or parasitic infections. He or she may also wish to take a blood sample for testing.

Long-Term Outlook

Your future health outlook depends on what caused the foul-smelling stool. Most conditions that cause this symptom are treatable. However, diseases such as irritable bowel syndrome or Crohn’s disease may require lifelong changes to your diet or medications to control bowel movements and pain.


Making necessary dietary changes may help prevent foul-smelling stools. If you have a disease that affects the way you absorb food or the way your body reacts to eating certain foods, your doctor can devise a diet plan that’s right for you. Following this diet plan can help reduce symptoms such as abdominal pain, abdominal bloating, and foul-smelling stools.

Avoid bacterial infections from food by handling your food correctly. Cook raw foods like beef, poultry, pork, and eggs thoroughly before eating. This means checking your food’s internal temperature with a thermometer before eating. Consult your local health department for the minimum internal temperature each type of food must reach before you eat it. Do not drink raw (unpasteurized) milk. Do not prepare meat and vegetables on the same chopping board. Preparing them on the same board can spread salmonella or other bacteria. Wash your hands thoroughly after handling raw meats or using the restroom.

Content licensed from:

Written by: April Kahn
Published on: Sep 10, 2012on: Apr 14, 2016

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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