Digestive Disorders > Symptoms

Mucus in the stool – possible causes

Dr. med. Andre Sommer

Dr. med. Andre Sommer

Mucus admixtures in bowel movements can have a variety of causes. If they occur only occasionally and temporarily, they are usually no cause for concern. But mucus is also present in the stool with many serious diseases. Which diseases are involved, how do you recognize mucus as a symptom and how can mucus in stool be treated?

What is mucus?

Mucus is a viscous secretion **that is produced in the **mucous glands. Depending on the location of the mucus production (respiratory tract, gastrointestinal tract), it is composed differently. An important part of the mucus are so-called mucins, a group of proteins associated with sugars. They bind moisture and thus determine the consistency of the mucus. Mucus has a variety of functions in the body. It forms a protective layer **around sensitive tissue, protects against dehydration and can help to trap and render harmful microorganisms (bacteria, viruses) harmless. **Physiological mucus (not changed by disease) is usually clear and viscous.

What causes mucus in the stool?

There are many mucous glands in humans’ gastrointestinal tract. Their secretion helps to mix and digest the food pulp coming from the stomach effectively. It also increases the lubricity of the intestinal wall and thus helps to transport the digested food along the intestine to the anus. The amount of mucus is usually so small that it is not noticeable in the stool.

If there are visible mucus admixtures in the stool, this can have a variety of causes, such as:

  • dietary changes
  • food intolerances
  • infectious diseases
  • inflammatory bowel disease
  • cancers

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Cause Example Other symptoms
Dietary changes Very fatty meal, switching to a high-carbohydrate diet Rarely additional symptoms, passes after a few days
Food intolerance Lactose intolerance, gluten intolerance, food poisoning Often nausea, vomiting, gas, cramps, diarrhea
Infections Gastroenteritis, salmonellosis General feeling of sickness, abdominal pain, diarrhea
Inflammatory bowel disease Crohn's disease, ulcerative colitis Abdominal pain, bloating, diarrhea, blood in the stool
Cancer Colon cancer Small amounts of blood and mucus in the stool

Dietary changes

The simplest explanation of mucus in the stool is a change of diet. Eating a very fatty meal can lead to increased mucus in the stool. This appearance of mucus is temporary, however, and should quickly subside.

The change to a high-carbohydrate diet (bread, pasta, rice) can lead to a change in stool consistency and mucus admixtures in the first day. However, all dietary changes have in common that the mucus is only present for a short time during the changeover. If the mucus admixture persists for several days, there is often another cause.

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Food intolerances

Food intolerance is playing an increasingly significant role in western industrialized nations. Due to the large number of available and processed foods, it is more and more common that individual food components are not tolerated or people develop allergies against them.

In general, all food intolerances can lead to the appearance of mucus in the stool. It is therefore important to pay attention to whether the mucus admixtures in the bowel movements occur when you consume certain foods or whether additional symptoms such as nausea, vomiting, abdominal pain or flatulence occur.

The most important intolerances that can lead to mucus in the stool are:

Lactose intolerance

Patients with lactose intolerance lack the enzyme lactase in the intestine. Therefore, they cannot digest the lactose consumed with food. In Germany about fifteen percent of the adult population does not tolerate lactose. Since the body cannot absorb the lactose, it migrates from the small intestine to the large intestine. There it is processed by bacteria from the intestinal flora. The products of this processing cause bloating, abdominal cramps, nausea and diarrhea. In addition, the intestine can react with an increased production of mucus, which is noticed during bowel movements.

Gluten intolerance (celiac disease)

Celiac disease is hypersensitivity to the food protein gluten. The absorption of gluten leads to an immune reaction and the inflammation of intestinal mucosa. As a result of the inflammation, the mucous glands can be stimulated to produce more mucus. In addition to a variety of other symptoms, mucus admixtures also occur in the stool. Gluten intolerance is very rare, and wheat sensitivity, which is often mentioned in the media, is more common.

With food poisoning, for example, when eating spoiled seafood, mucus admixtures can also occur in the stool.

Infectious diseases

If the gastrointestinal tract is colonized by disease-causing organisms (pathogens), there is often an inflammatory response. Among other things, this inflammation causes the intestinal glands to produce more mucus.

The main infectious diseases that can lead to mucus in the stool are:


The term gastroenteritis describes aninflammation of the gastrointestinal tract. Mostly an infection with a virus (e.g. rotaviruses and novoviruses) is the trigger. The newspaper often reports about such outbreaks in facilities such as kindergartens or on cruise ships. In addition to a general feeling of illness, gastroenteritis also causes nausea, diarrhea and mucus in the stool. Gastroenteritis caused by viruses usually heals quickly, but you should pay attention to adequate hydration.


Salmonellosis is a special form of gastroenteritis that is caused by bacteria (Salmonella). Symptoms of salmonellosis are similar to those of gastroenteritis caused by viruses. However, it is usually more intense and can even be life-threatening in some cases.

Inflammatory bowel disease

The inflammatory bowel diseases, crohn's disease and ulcerative colitis, are rare compared to irritable bowel syndrome. Around 150 out of 100,000 people in Germany suffer from Crohn's disease. In the case of these diseases, the origin of which is not yet fully understood, the immune system attacks your own intestinal mucosa and leads to pronounced inflammatory reactions. As part of this inflammation, mucus can also be present in the stool. With Crohn's disease, vomiting, nausea, diarrhea and abdominal cramps often occur in addition to the addition of mucus. With ulcerative colitis, there is often also blood in the stool. Irritable Bowel Syndrome can also lead to increased mucus in the bowel movements. Here, however, the mucus should appear without the addition of blood and have a light, clear color.


Colon cancer is one of the most common cancers in Germany. The first symptoms of such a disease are usually small amounts of blood and mucus **that are added to the bowel movements. If these small amounts are noticed in the stool for some time, a doctor should be consulted. This then needs to be clarified with a **colonoscopy.


Are there differences in the type of mucus?

The composition of the mucus can vary depending on the trigger. Often the consistency and color of the mucus is the first indication of the cause of the mucus admixture The quantity of the mucus can also vary widely. Infectious diseases are often accompanied by a dilution of the mucus since the mucous glands produce watery mucus as a result of the inflammation. The color of the mucus provides an important indication of its cause. Normal mucus is bright and clear. The mucus admixtures as part of a change in diet are also similar. Light mucus can also occur with food intolerances. If this happens only occasionally, there is usually no danger. With prolonged occurrence or additional symptoms like nausea and vomiting, a doctor should be consulted quickly.

Whitish mucus in stool is also common in food intolerances and less common in inflammatory bowel disease such as Crohn's disease.

Yellow mucus often comes about as a result of dead white blood cells (Leukocytes). This provides an indication of an existing infection.

Red mucus in the stool comes through additional blood and occurs in inflammatory bowel diseases, some infections and cancer of the intestine.

Color of the mucus Composition Occurrence
Light mucus Normal mucus in the body Diet change, food intolerance
Yellow mucus Dead immune cells in the mucus (pus) Infections
Red mucus Blood in the mucus Inflammatory bowel disease, infection, cancer
Different colors Various food ingredients or colorants in the mucus Often through ingested food (e.g. spinach - green mucus)

How does the doctor find the cause of the mucus in the stool?

The color, consistency and amount of mucus give the doctor the first clues to the trigger. In addition, the doctor can arrange further examinations to determine the cause. In addition to a detailed physical examination, this can include an ultrasound of the gastrointestinal tract, blood tests and a colonoscopy. A combination of these examination methods can in most cases find the cause of the mucus admixture in the stool.

How can you treat mucus in the stool?

Because mucus in the stool is not a disease, but a symptom it is treated by eliminating the triggering disease. If it comes through a change in diet, it usually takes care of itself or can be remedied through more conscious nutrition. Talk to one of our experts for free to optimize your diet.

If infections are the cause, the mucus admixture will stop after the infection has healed. Other diseases, such as inflammatory bowel disease or colon cancer are harder to treat. However, here too, in close cooperation with the doctor, alleviation of symptoms and a higher quality of life can be achieved.

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Dr. med. Andre Sommer

Dr. med. Andre Sommer

I’m André, a medical doctor from Berlin. Together with a team of medical doctors, nutritionists and data scientists we empower people to understand digestive issues with our app Cara.

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