Causes of Diarrhea

Acute Diarrhea: There are various causes of sudden-onset acute diarrhea, such as:

Toxic Causes of Diarrhea: Various drugs, medications, poisons, toxins, and substances can cause diarrhea:

Infectious Causes of Acute Diarrhea: Various different infections of the gastrointestinal system may cause diarrhea (usually with other symptoms such as fever):

Chronic Diarrhea Categories: There are various disorders that may cause chronic diarrhea, with the main classes of disorder being:

Note that many of the causes of Acute Diarrhea may also sometimes cause Chronic Diarrhea, such as where an infection is low-level (subacute) and/or lasts for some time.

Chronic Gastrointestinal Disorders: Various chronic disorders of the digestive tract may result in chronic diarrhea, such as:

Tumors and Chronic Diarrhea: Some tumors and cancers may cause chronic diarrhea, such as:

Endocrine Disorders: Various endocrine disorders may cause chronic diarrhea, such as:

Note that some tumors cause endocrine imbalance, as in the separate list of tumor causes of chronic diarrhea.

Other Chronic Diarrhea Causes: Various causes of chronic diarrhea include:

Causes of Bloody Diarrhea: Various disorders may cause bloody diarrhea (including many on the list for diarrhea in general):

Bloody diarrhea may also occasionally occur as a combination of a disorder causing blood in stool combined with, or resulting from, a different disorder causing diarrhea. For example, straining with diarrhea may cause a rectal bleed, such as from a burst hemorrhoid or anal fissure. Read more about: Rectal bleeding

Similar Symptoms: See also the various causes of similar and related symptoms, such as:

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Back to: « Diarrhea

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What causes diarrhea?

Acute and persistent diarrhea may have causes that are different from those of chronic diarrhea. In many cases, doctors do not find the cause of diarrhea. Most diarrhea goes away on its own within 4 days, and finding the cause is not necessary.

Acute and persistent diarrhea

The most common causes of acute and persistent diarrhea are infections, travelers’ diarrhea, and side effects of medicines.


Three types of infections that cause diarrhea include

Infections in the digestive tract that spread through foods or drinks are called foodborne illnesses.

Infections lasting more than 2 weeks and less than 4 weeks can cause persistent diarrhea.

Travelers’ diarrhea

Travelers’ diarrhea is caused by eating food or drinking water contaminated with bacteria, viruses, or parasites. Travelers’ diarrhea is most often acute. However, some parasites cause diarrhea that lasts longer. Travelers’ diarrhea can be a problem for people traveling to developing countries.

Side effects of medicines

Many medicines may cause diarrhea. Medicines that may cause diarrhea include antibiotics , antacids containing magnesium, and medicines used to treat cancer.

Chronic diarrhea

Some infections, food allergies and intolerances, digestive tract problems, abdominal surgery, and long-term use of medicines can cause chronic diarrhea.


Some infections from bacteria and parasites that cause diarrhea do not go away quickly without treatment. Also, after an infection, people may have problems digesting carbohydrates such as lactose or proteins in foods such as cow’s milk, milk products, or soy . Problems digesting carbohydrates or proteins can prolong diarrhea.

Food allergies and intolerances

Allergies to foods such as cow’s milk, soy, cereal grains, eggs, and seafood may cause chronic diarrhea.

Lactose intolerance is a common condition that may cause diarrhea after eating foods or drinking liquids that contain milk or milk products.

Fructose intolerance is a condition that may cause diarrhea after eating foods or drinking liquids that contain fructose, a sugar found in fruits, fruit juices, and honey. Fructose is added to many foods and soft drinks as a sweetener called high-fructose corn syrup.

Sugar alcohols such as sorbitol, mannitol, and xylitol may cause diarrhea in some people. Sugar-free candies and gum often include these sugar alcohols.

Digestive tract problems

Digestive tract problems that may cause chronic diarrhea include

Abdominal surgery

You may develop chronic diarrhea after abdominal surgery. Abdominal surgery is an operation on the appendix, gallbladder, large intestine, liver, pancreas, small intestine, spleen, or stomach.

Long-term use of medicines

Medicines that must be taken for a long time may cause chronic diarrhea. Some medicines, such as antibiotics, can change the normal gut flora and increase your chances of infection with Clostridium difficile , a bacterium that can cause chronic diarrhea.

Source: NIDDK (NIH)1

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Acute diarrhoea may be a symptom of infection of the digestive system (gastroenteritis) which is usually caused by a virus, but sometimes is caused by bacteria or parasites. It may also occur in association with other communicable diseases such as measles and malaria.

Source: Queensland Health2

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Some medicines, including Alzheimer's medications, may cause diarrhea—loose bowel movements. Certain medical problems also may cause diarrhea. Make sure the person takes in lots of fluids when he or she has diarrhea. Also, be sure to let the doctor know about this problem.

Source: NIA (NIH)3

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What causes diarrhoea

Brief diarrhoea

Brief diarrhoea can result from infections or a reaction to some medicines.

Travel to new areas may cause an upset stomach (eg, from contaminated food or water).

Mild diarrhoea

Mild diarrhoea can result from an alcohol binge, emotional stress, an intolerance to certain foods, or food poisoning.

Chronic diarrhoea

Chronic diarrhoea can indicate medical problems, such as:

See your doctor if you’re worried about any of these.

Source: New Zealand Health4

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What causes diarrhoea

Diarrhoea is usually caused by a bowel infection. Other causes can be things like a food allergy, alcohol or appendicitis.

If you're taking any medicine, check the side effects. Diarrhoea might be one of them.

Source: NHS Choices UK5

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Conditions that can cause diarrhoea

Source: NHS Choices UK6

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Shigella: Shigellosis is an infectious, diarrheal disease caused by a group of bacteria called Shigella. Shigella causes roughly 500,000 cases of diarrhea in the United States each year.

Source: NIAID (NIH)7

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Toddler’s diarrhea: Toddler’s diarrhea is a common cause of chronic diarrhea in toddlers (ages 1 to 3), and preschool-age children (ages 3 to 5).

Source: NIDDK (NIH)8

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Food allergies, Food intolerances: Food allergies, lactose intolerance, fructose intolerance, and sucrose intolerance are common causes of chronic diarrhea.

Source: NIDDK (NIH)9

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Chronic constipation: Sometimes chronic constipation in children can lead to "overflow’ of loose poos which looks like diarrhoea.

Source: New Zealand Health10

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Colon cancer: Its first symptoms may be a change in bowel habits - either diarrhoea or constipation, sometimes with blood or mucus (slime).

Source: New Zealand Health11

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Thyroid cancer: Rarely, thyroid cancer can affect the production of thyroid hormones and cause diarrhoea and flushing.

Source: NHS Choices UK12

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Wheat sensitivity: Bread-related gut symptoms

"Probably one-third of patients in my allergy clinic complain of digestive symptoms such as bloating, diarrhoea, vomiting and stomach pain after eating bread," says Isabel Skypala PhD, specialist allergy dietitian at the Royal Brompton and Harefield NHS Foundation Trust.

She says allergy is unlikely to be the culprit, but bread-related symptoms are real and wheat could be to blame.

"Some people find certain foods are simply hard to digest and wheat appears to be one of those," she explains.

Read more about food intolerance.

Source: NHS Choices UK13

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Rotavirus: Rotavirus is the most common cause of gastroenteritis in infants and very young children.

Source: GOV.UK14

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Some causes may include:15 Causes of Diarrhea:

Causes List for Diarrhea

List of possible causes of Diarrhea or similar symptoms may include:16

... Full Causes List for Diarrhea »

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  1. Source: NIDDK (NIH): health-information/ digestive-diseases/ diarrhea/ all-content
  2. Source: Queensland Health: HealthCondition/ condition/ 14/ 33/ 39/ diarrhoea-in-young-children
  3. Source: NIA (NIH): health/ alzheimers-disease-common-medical-problems
  4. Source: New Zealand Health: your-health/ conditions-and-treatments/ diseases-and-illnesses/ diarrhoea
  5. Source: NHS Choices UK: conditions/ Diarrhoea/ 
  6. ibid.
  7. Source: NIAID (NIH): diseases-conditions/ shigellosis
  8. Source: NIDDK (NIH): health-information/ digestive-diseases/ chronic-diarrhea-children/ all-content
  9. ibid.
  10. Source: New Zealand Health: your-health/ conditions-and-treatments/ diseases-and-illnesses/ constipation
  11. ibid.
  12. Source: NHS Choices UK: conditions/ thyroid-cancer/ symptoms/ 
  13. Source: NHS Choices UK: Livewell/ digestive-health/ Pages/ cutting-out-bread.aspx
  14. Source: GOV.UK: government/ collections/ rotavirus-guidance-data-and-analysis
  15. Source: Human Phenotype Ontology
  16. Source: Algorithmically Generated List

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.