Foul Smelling


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By Medicover Hospitals / 29 Feb 2021
Home | symptoms | foul-smelling
  • Stool normally has an unpleasant odor. The foul-smelling stool has an unusually strong putrid odor. Most of the time, foul-smelling stools are caused by the foods people eat and the bacteria in their colon. However, foul-smelling stools can also present a serious health problem. Diarrhea, bloating, or gas can occur with foul-smelling stools. These stools are often loose or runny.
  • Article Context:

    1. What are foul-smelling stools?
    2. Causes
    3. Diagnosis
    4. Treatment
    5. When to visit a Doctor?
    6. Prevention
    7. FAQ's

    What are foul-smelling stools?

  • The foul-smelling stool is the odor associated with stool or feces. The stools normally have an unpleasant odor.
  • Stools form in the large intestine (colon), which is part of the digestive system. Normally, the "good bacteria" live in your large intestine and help digest or break down food scraps that enter the large intestine from the small intestine. Stools form during this process. Stool passes through the large intestine to the rectum for elimination from the body. The normal, unpleasant odor associated with stool is the result of bacteria.
  • Changes in stool odor can be caused by the foods you eat. Even extremely foul-smelling stools can be caused by changes in your diet. However, abnormally foul-smelling stools can also be a sign of an illness, disorder, or condition. Examples include celiac disease, Crohn's disease, cystic fibrosis, and intestinal infections. Due to the range of possible causes of a bad stool odor, correct diagnosis of the underlying disease, disorder, or condition is very important. Contact your healthcare professional for a physical exam.
  • In some cases, foul-smelling stools can be a sign of a serious or life-threatening illness, such as a gut infection, abscess, or blockage. See a doctor right away if you have foul-smelling stools accompanied by severe symptoms, such as severe abdominal pain, cramping, and bloody stools. See a doctor promptly if your stool odor is unusual, unexplained, or persistent, or worries you.
  • Causes:

    Antibiotics and infection:

  • People who take antibiotics may experience temporary stomach pain and foul-smelling stools. This is because antibiotics can upset the delicate balance of good and bad bacteria in the gut.
  • Signs usually go away soon after antibiotic treatment, once the good bacteria in the gut have built up.
  • Sometimes antibiotics can destroy so many good gut bacteria that the harmful bacteria grow out of control, causing infection.
  • People who experience an overgrowth of harmful gut bacteria while taking antibiotics may notice the following signs:
    • watery, foul-smelling diarrhea, which may contain pus or blood
    • pain, tenderness, and cramps in the abdomen
    • fever

    Lactose intolerance:

  • Lactose is a type of sugar found in milk and other dairy products. The human body breaks down lactose and an enzyme called lactase digests it.
  • A person who is lactose intolerant does not make enough lactase to digest lactose.
  • People who are lactose intolerant may experience the following signs after consuming dairy products:
    • loose, foul-smelling stools
    • bloating and gas
    • abdominal cramps
    • nausea

    Milk allergy:

  • The American College of Allergy, Asthma & Immunology (ACCAI) explains that having a milk allergy is not the same as lactose intolerance.
  • People who are allergic to milk have an immune reaction to milk and milk products.
  • PSigns of milk allergy include:
    • bloody and foul-smelling stools
    • stomach ache
    • vomiting
    • urticaria
    • anaphylaxis, a rare but potentially fatal allergic reaction

    Short Bowel Syndrome:

  • Short bowel syndrome (SBS) is a rare condition that occurs when part of the small or large intestine is missing or unable to function.
  • Because of this, people with SBS often suffer from malabsorption, which can lead to serious complications.
  • SBS can occur for many reasons. A common cause is the surgical removal of part of the intestine after treatment for inflammatory bowel disease (IBD).
  • Signs of SBS vary among people, but can include:
    • pale, oily, and foul-smelling stools
    • severe diarrhea
    • dehydration
    • weight and muscle loss
    • lethargy
    • malnutrition
    • bloating
    • stomach pains

    Chronic pancreatitis:

  • Chronic pancreatitis is a persistent inflammation of the pancreas that gets worse over time. Chronic pancreatitis causes irreparable damage, which affects a person's ability to digest food and make pancreatic hormones.
  • Signs may include:
    • oily, greasy, and foul-smelling stools
    • nausea
    • vomiting
    • pain in the upper abdomen and back, which gets worse with eating or drinking
    • pale or clayey stools
    • malnutrition and weight loss


    Antibiotics and infection:

  • In most cases, a doctor can diagnose stomach pain associated with antibiotics by doing a physical exam and asking about a person's history of antibiotic treatment. They may also request a stool sample to check for bacterial toxins.
  • Lactose intolerance:

  • People who suspect they are lactose intolerant should eliminate all dairy products from the diet for several days. After the dairy-free period, a person should reintroduce milk or dairy products to see if the symptoms return.
  • Other diagnostic tests include:
    • Blood test: This shows whether or not a person can successfully digest lactose after consuming products that contain it.
    • A hydrogen breath test: This involves a person repeatedly blowing a bag after consuming lactose. If the collected air contains high levels of hydrogen, this indicates lactose intolerance.
    • A stool acidity test: This is a test of a person's stool after ingesting lactose. A very acidic stool sample indicates lactose intolerance.
    • A genetic test: This involves analyzing a sample of blood or saliva for a gene linked to lactose intolerance.
    • Surgical biopsy of the intestine: This involves a surgeon removing a small piece of the intestine for analysis.

    Milk allergy:

  • According to the ACCAI, diagnostic tests include:
    • Skin test: A doctor dabs some milk on the person's arm, then lightly pricks the area with a needle. Irritation at the site indicates an allergy.
    • Blood test: This checks for antibodies to immunoglobulin E, which the body produces in response to allergens.
    • Oral food challenge: A person consumes a small amount of the allergen in the presence of a doctor or allergist.

    Short bowel syndrome:

  • A doctor may order the following tests to help diagnose SBS:
    • Blood tests: These can check for anemia, malnutrition, and dehydration.
    • Imaging techniques(abdominal x-rays and CT scans): These can check for obstructions and loss of bowel function.
    • Liver biopsy: This can check liver function.

    Chronic pancreatitis:

  • A doctor will do a physical exam and take a thorough medical history. They may also order the following diagnostic tests:
    • CT scan
    • Magnetic resonance cholangiopancreatography, a type of MRI scan that uses a dye to make it easier to see internal organs
    • Abdominal ultrasound
    • Endoscopic ultrasound, in which a doctor inserts a flexible tube, or endoscope, into the small intestine through your mouth


    Antibiotics and infection:

  • In most cases, symptoms go away soon after a person finishes antibiotic treatment. In the meantime, the following home treatments may help reduce the severity of symptoms:
    • drink lots of fluids
    • avoiding wheat, dairy, and foods high in fiber, which can further irritate the intestines

    Antibiotics and infection:

  • In most cases, symptoms go away soon after a person finishes antibiotic treatment. In the meantime, the following home treatments may help reduce the severity of symptoms:
  • Or people can buy tablets that contain the enzyme lactase. Taking the pills before eating dairy products can help the body digest lactose.
  • Milk allergy:

  • The only way to manage a milk allergy is to avoid milk and products containing milk.
  • The ACCAI also notes that a doctor or allergist may advise someone with an allergy to milk to carry an epinephrine pen. These allow a person to self-inject epinephrine in the event of anaphylactic shock.
  • Short bowel syndrome:

  • Doctors usually tailor treatment for SBS to a person's symptoms and the amount of bowel they affect. Some treatment options include:
    • anti-diarrheal drugs
    • medicines to replace the intestinal lining
    • dietary adjustments
    • intravenous fluids
    • surgery

    Chronic pancreatitis:

  • According to the National Pancreas Foundation, treatments for chronic pancreatitis focus on pain relief. They may include:
    • take pain relievers
    • undergoing a Whipple procedure or surgery to remove pancreatic lesions
    • having a pancreatectomy or surgery to remove all or part of the pancreas

    When to visit a Doctor?

  • Visit to doctor if you experience any of these:
    • Black or pale stools often
    • Blood in the stool
    • Changes in the stool related to diet
    • Chills
    • Cramping
    • Fever
    • Pain in the abdomen
    • Weight loss


  • Here are some ways to prevent foul-smelling stools:
  • Make dietary changes:

    • Making dietary changes can help prevent foul-smelling stools. For example, avoid drinking raw or unpasteurized milk.
    • If you have a condition that affects the way you absorb food or the way your body responds to eating certain foods, your doctor can create a diet that is right for you.
    • Following this diet plan can help reduce symptoms such as:
      • abdominal pain
      • abdominal bloating
      • foul-smelling stool
    • For inflammatory bowel disease (IBD), you can follow a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs).

    Handle food correctly:

    • Avoid bacterial infections in your food by handling it properly. Cook raw foods well before eating them. Examples include:
      • beef
      • poultry
      • pork
      • eggs
    • Cooking well means checking the internal temperature of your food with a thermometer before you eat it.
    • Check with your local health department for the minimum internal temperature each type of food should reach before eating it.
    • Do not prepare meat and vegetables on the same cutting board. Preparing them on the same board can spread Salmonella or other bacteria.
    • You should also wash your hands thoroughly after handling raw meat or using the toilet.

    Frequently Asked Questions:

  • Giardiasis is an infection caused by a parasite called Giardia. This causes diarrhea. Signs include explosive, watery, greasy, and foul-smelling stools, bloating, nausea, pain, gas, fatigue, and loss of appetite.
  • Most of the time, smelly poop is caused by your diet. This could be caused by eating certain foods or being lactose intolerant. But if it smells bad regularly, you may have an imbalance in your microbiome or a disease like inflammatory bowel disease. Occasional foul-smelling stools may not require treatment.
  • Black, tarry-textured, foul-smelling stools are often a symptom of upper gastrointestinal bleeding from the esophagus, stomach, or small intestine. This is called melena. Rectal bleeding of bright red blood with clots, sometimes mixed with stool, is called hematochezia.
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