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Causes of Diarrhea

Diseases and Conditions That Cause Diarrhea


Updated May 19, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Diarrhea is a common, yet rarely discussed problem. It is a symptom of an underlying condition, which can take some work to identify. There are many possible causes of diarrhea.

Causes of Diarrhea That Starts Suddenly (Acute Diarrhea)

The most common cause of diarrhea, especially diarrhea that starts suddenly, is an infection - by bacteria, virus, or parasite. There are many possible causes of acute diarrhea, but the three most common are:

Food Poisoning
Food poisoning occurs when you eat food that is contaminated with bacteria. The bacteria build up toxins in the food that make you sick. Causes of food poisoning are poor sanitation or food being stored at the wrong temperature.

  • How long diarrhea lasts: Usually less than 2 days
  • Triggered by: Toxins in food
  • Symptoms appear within: 2 to 6 hours
  • Appearance: Explosive, watery
  • Other symptoms: Abdominal cramps, fever, vomiting, weakness

Traveler’s Diarrhea
Traveler’s diarrhea is caused by eating food or drinking water that is contaminated with bacteria or parasites. Most traveler’s diarrhea will get better with home care in a few days. If you have recently traveled to a tropical country, and you have diarrhea, call your doctor.

  • How long diarrhea lasts: Usually less than 1 week
  • Triggered by: Food or water that is contaminated by bacteria, viruses, or parasites
  • Symptoms appear within: 12 to 24 hours
  • Appearance: Explosive, watery, sometimes contains mucous or blood
  • Other symptoms: Possibly vomiting and/or fever

Stomach Flu
Stomach flu is caused by different viruses than seasonal flu, such as rotavirus. You can generally care for your stomach flu with home treatment. Young children, the elderly, and people with compromised immune systems are at risk for dehydration, and should be watched closely for signs of more serious complications.

  • How long diarrhea lasts: Usually 3 – 8 days
  • Triggered by: A virus
  • Symptoms appear within: 2 days after exposure
  • Appearance: Watery
  • Other symptoms: Vomiting, fever, achiness

Causes of Chronic Diarrhea

Diarrhea that goes on for weeks or months may be caused by an infection, or it may be caused by an underlying medical condition. Here are some of the possible causes of chronic diarrhea and there are many more. If you have had diarrhea for more than three days, seek help from your doctor.

Celiac Disease
If you have untreated celiac disease, you may have a hard time linking your symptoms with a specific food because your gut is damaged and you may experience symptoms all the time.

  • How long diarrhea lasts: More than 4 weeks
  • Triggered by: Gluten, but may hard to pinpoint to a specific meal
  • Appearance: Large, bad-smelling stools that float in water
  • Other symptoms: Unintended weight loss, lack of energy, lack of growth in children

Food Allergy
Symptoms of classic Ig-E mediated food allergy begin within minutes to hours of eating a trigger food. It is possible to be allergic to any food, but a few foods cause the most common food allergies.

  • How long diarrhea lasts: Usually less than 24 hours
  • Triggered by: A specific food
  • Symptoms appear within: 2 hours
  • Appearance: Watery, may contain blood
  • Other symptoms: Hives; vomiting; swelling of face, tongue or throat; eczema

Food Intolerance
Food intolerance is caused by a lack of the enzymes needed to digest a specific food. Lactose intolerance, the inability to digest the sugars in milk, is the most common.

  • How long diarrhea lasts: More than 4 weeks
  • Triggered by: A specific food
  • Symptoms appear within: 2 to 12 hours
  • Appearance: Watery, sometimes contains mucous
  • Other symptoms: Gassiness, abdominal cramps or pain

Inflammatory Bowel Disease
Inflammatory bowel disease includes Crohn's disease and ulcerative colitis, both of which have chronic diarrhea as a symptom. Both are incurable chronic diseases of the digestive tract that may be treated with surgery or managed with medication.

  • How long diarrhea lasts: More than 4 weeks
  • Triggered by: Not related to a specific food
  • Appearance: Blood or mucous in stool
  • Other symptoms: Abdominal pain, fever, weight loss, delayed growth in children

Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) describes chronic diarrhea, constipation, and abdominal pain that does not have a known disease as a cause. If you have been diagnosed with IBS, discuss the possibility of celiac disease with your doctor. The American College of Gastroenterology recommends that anyone diagnosed with IBS and diarrhea be tested for celiac disease.

  • How long diarrhea lasts: At least six months
  • Triggered by: Not related to a specific food, though certain foods may aggravate symptoms
  • Appearance: Small, frequent stools
  • Other symptoms: Chronic abdominal bloating or distention, constipation. Pain is relieved by bowel movement

Milk/Soy Protein Intolerance
Infants usually show signs of protein intolerance within a few months of birth. Some infants may react to food proteins present in breastmilk, while others may react to formulas based on either cow’s milk or soy.

  • How long diarrhea lasts: More than two weeks
  • Triggered by: Dairy or soy products, sometimes by egg or other proteins
  • Symptoms appear within: 2 hours or more
  • Appearance: Streaks of mucous or blood
  • Other symptoms: Distended belly, crying, failure to thrive

Some medications, in particular antibiotics and chemotherapy, can cause diarrhea. You may have a reaction to the medication itself or an additive, such as a flavoring. The medication can also alter the balance of bacteria in your gut, causing abdominal pain and diarrhea. Talk to your doctor if you have diarrhea after starting a new medication.

Other Causes of Diarrhea

There are many other possible causes of diarrhea. For more information, check your symptoms with our symptom checker.

What Your Doctor Will Ask About Your Diarrhea

In order to figure out the cause of your diarrhea, your doctor is likely to ask you these questions:

  • How long have you had diarrhea? While not an absolute rule, diarrhea that started suddenly in the last 24 hours may indicate an infection or virus. If it has been going on for months or years, you may have a food intolerance or inflammatory bowel disease.

  • When did it begin? You doctor will want to know if you were traveling out of the country recently or if you ate any foods you suspect are causing your diarrhea. Food allergy symptoms begin immediately after eating a food, while diarrhea caused by intolerances or infections may be delayed by 12 hours or more.

  • How many stools a day are you having? The number of stools a day that healthy people have averages between 2-3 per day and 2-3 per week. Three or more unformed stools a day is the cutoff for diarrhea.

  • What does it look like? Diarrhea may be loose stools, watery, mucousy, or dark colored. Black or bright red diarrhea may mean there is blood in your stool, which is a serious condition that needs immediate medical care.

Treatment for Diarrhea

You can care for most diarrhea using at-home treatments, but some symptoms need immediate medical care.


American Gastroenterological Association. Understanding Food Allergies and Intolerances. Accessed 11/5/2010. http://www.gastro.org/patient-center/diet-medications/food-allergies-fructose-intolerance-and-lactose-intolerance

Center for Disease Control and Prevention. Guidelines for the Management of Acute Diarrhea. Accessed 11/5/2010. http://emergency.cdc.gov/disasters/hurricanes/pdf/dguidelines.pdf

Jutabha, R.,MD, Etiology of lower gastrointestinal bleeding in adults. UpToDate.com, accessed 11/5/2010. http://www.uptodate.com/patients/content/topic.do?topicKey=~hakksDf4t24eq&source=see_link

Medline Plus. Diarrhea. Accessed 11/5/2010. http://www.nlm.nih.gov/medlineplus/ency/article/003126.htm

Merck Manual Online. Accessed 11/5/2010. http://www.merck.com/mmpe/sec02/ch008/ch008c.html

Sicherer, Scott H. Clinical Aspects of Gastrointestinal Food Allergy in Childhood. Pediatrics 2003;111;1609-1616

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