Diarrhea is a condition in which bowel movements are abnormally frequent and stools are abnormally fluid. It is not a disease in and of itself, but it is usually a symptom of some underlying disorder. Diarrhea may be a result of food poisoning, infection, diseases such as dysentery or cholera, emotional upset, or many other conditions.

What Is Diarrhea?

Diarrhea is very common and is a condition with which almost everyone is familiar. Usually it is little more than an unpleasant nuisance that briefly interferes with work or play. Sometimes, however, severe attacks can seriously endanger a person's health by causing dehydration * . Diarrhea can last different lengths of time; it may be acute (sudden onset and short term) or chronic (recurrent and long lasting).

Diarrhea develops in the small or large intestines. The intestines may become irritated and inflamed by an infection or by certain foods. The inflamed intestine does not reabsorb as much water from the stool (bowel contents) as it normally would. In some infections, the intestines actually add more water to the stool. This extra water makes the stools very loose.

Bouts of diarrhea that range from mild to severe can be caused by several types of infectious microorganisms * (my-kro-OR-gan-iz-ims) in contaminated food or water. Diarrhea can also result from the body having trouble digesting dairy products or other foods. Mild cases of diarrhea can be caused by eating spicy food or by anxiety about some stressful event, such as having to give a speech in front of a lot of people.

What Causes Diarrhea?

There can be many causes of diarrhea. Some of them include food poisoning, dysentery, cholera, giardiasis (jee-ar-DY-a-sis), traveler's diarrhea, lactose intolerance, malabsorption/maldigestion, and antibiotic-induced diarrhea.

Food Poisoning

Everyone has heard of a party at which a lot of people got sick after eating the same food. Foods that are not cooked thoroughly or are not kept refrigerated until just before serving can cause food poisoning. It is important to make sure raw meat or poultry does not come in contact with cooked foods, that hands are washed thoroughly before handling any foods, and that all dishes and utensils are washed thoroughly after they have been in contact with raw meat or poultry. These measures help prevent food poisoning.


Dysentery is an intestinal infection that causes severe diarrhea, often with blood, pus, and mucus in the stools. It is especially common in poor countries with inadequate sanitation facilities, which causes the food and water supply to be contaminated. The most common causes of dysentery are bacteria and amoebas * . Amoebic dysentery can cause chronic diarrhea.


Outbreaks of cholera often accompany natural disasters such as earthquakes and storms that disrupt sanitation and cause food and water to be contaminated. It also is widespread in refugee camps and during other wartime situations in which people live in severely overcrowded conditions. Food and water contaminated by the cholera bacteria cause a watery form of diarrhea that can rapidly lead to death from severe dehydration.


Giardiasis is mainly a tropical disease that can give rise to severe diarrhea. Caused by a parasite * , it usually enters the body in contaminated drinking water. Travelers to tropical countries can develop this form of diarrhea, but it can also be contracted in more temperate areas.

During the 1990s and into the next decade, giardiasis became increasingly prevalent in developed countries such as the United States, especially among preschool children. In settings such as households and day-care centers, where children are in close contact, giardiasis can be caught by touching stool-contaminated objects or from hand-to-hand contact.

Chronic Diarrhea

Causes of Diarrhea

Causes of Diarrhea
Table by GGS Information Services. © 2016 Cengage Learning®.
Traveler's Diarrhea

Traveling to foreign countries and drinking water or eating foods washed in the local water supply can cause digestive upsets that include diarrhea; these are sometimes called traveler's diarrhea.

Often, the exact cause of traveler's diarrhea cannot be determined. Likely suspects are certain viruses and strains of bacteria such as E. coli that are present in the local water supply. Sometimes parasites such as Giardia lamblia and amoebas such as Entamoeba histolytica may cause traveler's diarrhea. Diarrhea caused by such parasites usually lasts longer than traveler's diarrhea caused by other substances. Other causes of traveler's diarrhea may include changes in diet, excessive alcohol intake, and Salmonella or Shigella bacteria.

Traveler's diarrhea usually occurs about one week after a person enters the foreign country. People who travel to Latin America, Africa, and Southeast Asia have a high risk for developing traveler's diarrhea.

Lactose Intolerance

Sometimes people get diarrhea from eating dairy products such as milk, cheese, and ice cream. This condition occurs because there is a sugar in milk and milk products called lactose (LAK-tos) that some people cannot digest. To be able to digest this sugar, there must be an enzyme * in the body called lactase (LAK-tays). Some people do not make enough of this enzyme, and when they drink milk or eat milk products they get diarrhea.

Malabsorption and Maldigestion

Many diseases can interfere with the intestine's ability to digest (break down) foods or absorb (soak up) digested foods. Problems associated with breaking down foods are called maldigestion (mal-di-JES-chun). Failure to absorb digested foods is called malabsorption (mal-ab-SORP-shun). If foods are not properly digested and absorbed, diarrhea may occur. Problems with the pancreas, Crohn's disease, and lactose intolerance are some of the medical conditions that cause digestion or absorption problems.

Antibiotic-Induced Diarrhea

Antibiotics are medicines that kill bacteria, and diarrhea is a common side effect of antibiotics. This condition occurs because antibiotics kill both the bad bacteria that make people sick and the good bacteria that live in the large intestine. Good bacteria help keep unhealthy, disease-causing bacteria from growing too much. An overgrowth of certain unhealthy bacteria, such as Clostridium difficile, can cause diarrhea. Good bacteria also add thickness, or bulk, to the stools, which makes them less watery.

Diarrhea in Infants
Did You Know?

More people died from unsanitary conditions during the American Civil War than from bullets. Of the estimated 600,000 fatalities during the war, the majority were the result of epidemics of diarrhea-inducing diseases such as dysentery and typhoid fever. These diseases were caused by contaminated food and water in the encampments. A voluntary organization called the U.S. Sanitary Commission was founded to combat the conditions and provide medical assistance; it also held sanitary fairs to raise money.

Is Diarrhea Contagious?

Depending on the underlying cause, diarrhea can be extremely contagious. Many of the viral and bacterial infections that cause diarrhea can be transmitted from person to person, although proper hygiene (thoroughly washing hands after using the bathroom or before handling foods) will help to prevent transmission.

How Do People Know They Have Diarrhea?

Although diarrhea may occur by itself, often it is accompanied by abdominal pain, gurgling bowel sounds, nausea, vomiting, and general weakness. The stools, or bowel movements, are loose or watery and may contain blood, pus, mucus, or droplets of fat. Sometimes attacks of diarrhea alternate with periods of constipation.

How Do Doctors Diagnose and Treat Diarrhea?


Most cases of diarrhea are mild and do not require medical attention. A doctor should be consulted if the diarrhea lasts more than a few days, recurs, or has blood in the stool. For infants, medical advice should be sought if the diarrhea lasts more than 48 hours. Medical tests used in diagnosis may include examination and culture of stool samples (for bacteria, viruses, or parasites), x-rays, or the use of a colonoscope (ko-LON-oskope), which is an instrument for viewing the lining of the colon.


Changes in diet may be recommended to determine whether diarrhea is a result of a food allergy, or problems digesting or absorbing foods. For example, diarrhea symptoms may get better if a person with lactose intolerance avoids milk products.

Treatment of diarrhea consists mainly of drinking liquids to replace lost fluids and prevent dehydration. The World Health Organization's salt, sugar, and water formula is commonly used to hydrate (add water to) children with severe diarrhea. It is easy to use and is inexpensive, and has helped save the lives of millions of people around the world.

In some cases, doctors may prescribe medications that ease mild diarrhea symptoms. Treatment of severe diarrhea depends largely on the cause. For example, antibiotics may be prescribed for dysentery or certain kinds of food poisoning.

Milk products, greasy foods, and sweets can make diarrhea worse. Such foods and drinks should be avoided until after the diarrhea stops. Some doctors recommend that children who are recovering from diarrhea eat bananas, plain rice, applesauce, and toast (known to parents as the B-R-A-T diet). Adults may add other soft, nonspicy foods to their diet as symptoms lessen. Such foods include boiled potatoes and baked, skinless chicken.

Can Diarrhea Be Prevented?

Washing one's hands thoroughly after using the toilet or changing an infant's diaper is always important but especially so where contagious forms of diarrhea such as giardiasis can be spread. Also, people should wash their hands thoroughly before and after handling foods, especially raw meat and poultry. Travelers in foreign countries should drink bottled water (not tap water), even for brushing teeth, and avoid eating raw meats, fish, fruits, and vegetables. Medicines may be given to prevent traveler's diarrhea in persons at high risk for the condition or who have certain medical conditions that can be made worse by diarrhea or dehydration.

People should be cautious about eating foods that are left out of the refrigerator for a long time. Bacteria thrive in warm temperatures. Leftovers should be refrigerated quickly. All food preparation surfaces, including cutting boards and countertops, should be washed before and after food preparation.

See also Cholera • Food Poisoning • Giardiasis • Irritable Bowel Syndrome • Maldigestion and Malabsorption Syndromes: Overview • Travel-Related Infections: Overview


Books and Articles

Arranga, Teri, Claire I. Viadro, and Lauren Underwood, eds. Bugs, Bowels, and Behavior: The Groundbreaking Story of the Gut–Brain Connection. New York: Skyhorse, 2013.

Enders, Giulia. Gut: The Inside Story of Our Body's Most Underrated Organ. Vancouver, BC: Greystone Books, 2015.


American College of Gastroenterology. 6400 Goldsboro Rd., Suite 200, Bethesda, MD 20817. Telephone: 301-263-9000. Website: http://patients.gi.org (accessed December 5, 2015).

* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive loss of body fluids that are not replaced, and occurs through sweating, vomiting, or diarrhea.

* microorganisms are tiny organisms that can only be seen using a microscope. Types of microorganisms include fungi, bacteria, and viruses.

* amoebas (uh-MEE-buz) are small, one-celled animals that live in fresh- and saltwater. Amoebas can only be seen with a microscope.

* parasite (PAIR-uh-site) is an organism such as a protozoan (a one-celled animal), worm, or insect that must live on or inside a human or other organism to survive. An animal or plant harboring a parasite is called its host. A parasite lives at the expense of the host and may cause illness.

* enzyme (EN-zime) is a protein that helps speed up a chemical reaction in cells or organisms.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)