Mucus in the stool is usually a sign of infection or another abnormality in the intestines, such as an intestinal ulcer or irritable bowel syndrome. Patients diagnosed with a food intolerance or with Crohn’s disease may also notice mucus in the stool, which may be accompanied by blood.

Mucus s a naturally-occurring substance that helps stools move through the intestine. It is normally produced in low quantities (just enough to lubricate the intestines) and therefore isn’t usually easily seen by the naked eye.

If you see mucus in your stool, you should consult your doctor or gastroenterologist for a thorough assessment and to identify if there is a more serious problem that needs to be treated.

What causes mucus in the stool?

The most common causes of stools with mucus are:

1. Food intolerance

Food intolerances and allergies to food containing lactose, fructose, sucrose, or gluten, for example, can cause inflammation of the intestinal walls. This can increase mucus production, which will cause mucus to be seen in the stools.

In these cases, there may also be other symptoms such as bloating, diarrhea, red spots on the skin, excessive gas, or constipation.

What to do: if you suspect you have an intolerance to any type of food, you should see a gastroenterologist for an intolerance test to confirm diagnosis. In the meantime, if you feel that you have a gluten intolerance, check-out our online symptom checker to assess your risk.

2. Gastroenteritis

Gastroenteritis occurs when a foreign microorganism (e.g. bacteria or a virus) infects the stomach and intestine. This can cause intense nausea, diarrhea, vomiting, loss of appetite and abdominal pain, as well as excess mucus in the stools.

This type of problem usually occurs when contaminated food or water is ingested, but it can also happen after prolonged use of antibiotics.

What to do: if gastroenteritis is suspected, it’s important to see your family doctor or gastroenterologist to confirm a diagnosis and start the appropriate treatment. Treatment can vary depending on severity - mild cases will only require fluid replacement, while other cases may need antibiotics (if the infection is bacteria-related). Read about home remedies for stomach and intestinal infections that you can prepare at home to complement your medical treatment.

3. Irritable bowel syndrome (IBS)

IBS results in inflammation of the intestinal mucosa, which will increase quantities of mucus in the stools. Although this can happen in all cases of IBS, mucus is more common in people who have long flare-ups with diarrhea.

Other common symptoms of those suffering from IBS include excess gas, bloating, and bouts of diarrhea that alternate with constipation, especially during periods of high stress or anxiety.

What to do: if IBS has already been diagnosed, try to participate in stress-reducing activities and ensure you follow an IBS diet (e.g. avoiding coffee, avoid fatty foods and spices, etc.). If you suspect you may have IBS, you should see your doctor or gastroenterologist for assessment, and start treatment as indicated.

4. Crohn’s disease

Crohn’s disease is a chronic bowel disease that result in constant inflammation of the intestinal walls. Crohn’s is characterized by symptoms like mucus in the stools, severe abdominal pain, fever, bloody diarrhea, and weakness.

What to do: treatment for Crohn’s disease usually includes changes in eating habits, such as controlling the amount of fiber ingested and reducing intake of fatty foods and dairy products. Read more about the Crohn's disease diet that your doctor may advise.

5. Bowel obstruction

A bowel obstruction occurs when the passage of stools through the intestine is blocked. The most common causes include hernias, a twisted bowel, eating a foreign object, and an intestinal tumor.

In these cases, mucus is produced in high quantities to try to push the stools forward, however they often remain in place with the mucus. This results in symptoms like bloating, severe abdominal pain, excess gas, and a decreased number of stools.

What to do: bowel obstruction is an emergency situation that needs to be treated immediately to avoid serious complications such as dilation or rupture of the intestine. If you suspect you have a bowel obstruction, go immediately to the hospital.

6. Anal fissure

An anal fissure is a relatively common problem that consists of a small wound near the anus. It usually occurs due to excessive bowel movements, like frequent diarrhea, for example. However, a fissure can also be caused by constipation, as straining to pass hard stools can end up damaging the sphincter.

With fissures, many symptoms can occur, like bright red blood in the stools, pain when pooping, mucus in the stools, and anal itching.

What to do: the most important things is to ensure adequate perianal hygiene. Taking sitz baths to relieve pain and applying ointments to heal the fissure more quickly are also beneficial. Alcoholic beverages and spicy foods should also be avoided - you should opt instead for a diet rich in fruits, vegetables, and whole grains.

7. Ulcerative colitis

Ulcerative colitis is an intestinal abnormality that causes ulcers in the bowels and persistent mucosal inflammation. People with ulcerative colitis often have blood, pus, or mucus in their stools.

Other symptoms that associated with ulcerative colitis include diarrhea, very severe abdominal pain, skin lesions, and weight loss.

What to do: the general recommendation is to increase the intake of fiber by eating foods such as papaya, lettuce, or chickpeas. This will help to make the stools bulkier and softer. Medication may be needed to relieve abdominal cramps or to stop diarrhea. Learn about the ulcerative colitis diet that your doctor may recommend.

8. Cystic fibrosis

Cystic fibrosis is a genetic disease that causes the body to produce thick, viscous mucus that is difficult to eliminate. It accumulates inside the organs, mainly in the lungs and gastrointestinal tract, causing respiratory and digestive symptoms.

This condition can lead to mucus obstructing the pancreatic ducts, causing poor food absorption, excess gas, diarrhea, constipation, abdominal pain and large oily stools with mucus.

What to do: you should consult a gastroenterologist so that the most appropriate treatment can be indicated. The doctor may prescribe digestive enzymes that facilitate digestion and nutrient absorption. In some cases, surgery may also be necessary.

9. Colon cancer

Colon cancer, or colorectal cancer, is a type of cancer that affects the large intestine. It can cause symptoms such as anemia, abdominal pain, weight loss, constipation, diarrhea and the presence of blood or mucus in the stool.

This type of cancer can occur in people who have risk factors, such as a family history of colon cancer, smoking, excessive consumption of alcohol and/or red meat, obesity and diabetes.

What to do: You should see a gastroenterologist if you suspect you may have colon cancer. The doctor will order testing, like a colonoscopy, to confirm a diagnosis, and to guide treatment, which may involve chemotherapy, radiation therapy and/or surgery.

When to see a doctor

In most cases, mucus in the stools is not serious, and is, almost always, easy to treat. However, you should monitor for large quantities of mucus that appear with symptoms like:

Stools with blood or pus;
Very severe abdominal pain;
Exaggerated abdominal distention;
Constant diarrhea.

If these additional symptoms emerge, you should go to the hospital or make an appointment with your doctor or gastroenterologist. These symptoms can be a sign of a more serious situation such as ulcerative colitis, Crohn’s disease, or even cancer.