Regular stools don’t have a pleasant odor, and there’s a good reason for that—stool is a product of bacteria in the colon breaking down digested food.
And this process of breaking down digested food comes with a not-so-rosy smell.
But most of us can recognize the difference between the way our stool usually smells and when something causes it to smell even worse than usual.
If you’re experiencing particularly foul-smelling stools, you may be wondering what’s behind them.
Changes in diet can cause especially foul-smelling stool, but there are other reasons for your stool to smell differently that may warrant medical attention.
Understanding the possible causes of foul-smelling stool can help you determine whether or not to seek advice from a medical professional.
What Causes Foul-Smelling Stool
There are several possible causes of foul-smelling stool.
Changes in diet can affect the way your stool smells.
For example, eating more spicy food or higher quantities of meat than you usually do will likely produce stronger smelling stools. Significant changes to your diet while traveling can also change the way your stool smells.
Eating foods that you’re allergic to or that your body has trouble processing can also produce foul-smelling stools. Specifically, eating foods with lactose if you’re lactose intolerant can result in foul-smelling stools.
Foul-smelling stools may also be a sign of an intestinal viral, bacterial (like E. coli or Salmonella), or parasitic infection.
These infections can occur after eating contaminated food or drinking contaminated water (which can also happen when swimming).
With an intestinal infection, you may have other symptoms, like severe stomach pain or cramps, diarrhea, nausea, or fever.
Malabsorption is a condition in which the body has trouble absorbing certain sugars, fats, proteins, or vitamins, which can cause foul-smelling stool.
Additional symptoms of malabsorption include chronic diarrhea, bulky stools, bloating, cramping, gas, and fatty stools.
Malabsorption can be caused by several diseases, including:
- Celiac disease
- Chronic pancreatitis
- Cystic fibrosis
- Crohn’s disease
- HIV or AIDS
- Chronic liver disease
- Ulcerative colitis
- Chronic pancreatitis
- Tropical sprue
- Short bowel syndrome
- Whipple disease
- Radiation treatment for cancer
Certain medications may also cause foul-smelling stools.
This can happen if you take a medication or supplement that contains an ingredient you’re allergic to, but it can also happen when you take antibiotics.
While on antibiotics, you may notice temporary foul-smelling stools that last until the natural balance of bacteria in your gut is restored.
What to Keep an Eye Out For
Changes in stool that are related to changes in your diet are usually temporary—once you return to your normal diet, your stool should return to its normal smell within a few days.
However, if your foul-smelling stool persists for several days regardless of a return to your normal diet, reach out to your healthcare provider for more information.
Additionally, there are some symptoms you should watch out for if you’re experiencing particularly foul-smelling poop:
- Black or pale-colored stool
- Blood in stool
- Body chills
- Abdominal cramping or pain
- Weight loss
If you experience any of the above symptoms, reach out to your healthcare provider as soon as possible.
When speaking with a healthcare professional about the cause of your foul-smelling stool, your provider will likely conduct a physical exam and ask you questions about your medical history.
They will also ask you questions specific to your changes in stool and diet. Questions you can expect to answer include:
- When did the change in your stool first take place?
- Are your stools a different color than usual?
- Are your stools a different consistency than usual or are they difficult to flush?
- Have there been any recent changes to your diet?
- Have you traveled recently?
- Are you experiencing any additional symptoms?
- Have you ever noticed a change in your stool’s smell in the past?
Depending on your answers, your provider may also ask for a stool sample to check for a bacterial, viral, or parasitic infection. Other tests may also be recommended.
There are several things you can do to help prevent an infection or reaction that can cause foul-smelling stool:
- Stick to a regular diet: Avoiding drastic changes to your diet can help to prevent foul-smelling stools.
- Avoid foods as recommended by your provider: If diagnosed with lactose intolerance, celiac disease, inflammatory bowel disease, or another condition, your provider may recommend following a specific diet (like avoiding dairy or gluten). Following this recommended diet closely can help to prevent foul-smelling stool and other bothersome symptoms that can impact your quality of life, like abdominal pain, bloating, and more.
- Handle food safely: Practicing good food hygiene can help prevent some bacterial infections, like E. coli and Salmonella infections. These practices include washing your hands thoroughly before food preparation, washing all produce before cooking or eating, cooking all meat to the minimum appropriate temperature using a meat thermometer, and using different cutting boards for meat and vegetable preparation.
- Use medications and supplements safely: Check with your provider before taking any medications or supplements to ensure that they are safe to take and will not cause unwanted side effects, like foul-smelling stool.
When to See a Doctor
If you’re experiencing foul-smelling stool that won’t go away, reach out to your provider for help.
It’s also important to seek immediate medical attention if you notice any additional symptoms, including bloody stool, fever, severe abdominal cramping, chills, or abnormally colored stools.
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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
E. Coli Infections. (2021.)
End Results: What color is your poop and other pressing fecal matters. (2018.)
Stools - foul smelling. (2022.)