• Diarrhoea is an abnormal increase in the frequency and liquidity of the stools.
  • It is a common problem that is usually not serious and can be effectively treated.
  • Severe or persistent diarrhoea (longer than 2 weeks) requires specific diagnosis and treatment.
  • Diarrhoea is not itself a disease, but can be a symptom of several underlying diseases.
  • Dehydration is a serious risk of severe diarrhoea, particularly in small children and the elderly.


Diarrhoea is an abnormal increase in the frequency and liquidity of the stools. The amount of water in the stool each day is generally not more than 200 ml for an adult. When it is above this amount, it is called diarrhoea. Some authorities consider stool frequency of > 3times per day as abnormal. However, any change in the frequency and consistency of stool to what is normal for that particular individual is relevant. Diarrhoea is not itself a disease, but can be a symptom of several underlying diseases. If a stool takes the shape of the container it is in – this is considered a diarrhoeal stool. 

Diarrhoea can be acute or chronic. Acute diarrhoea by definition lasts for less than 2 weeks and is usually self-limiting. Chronic or persistent diarrhoea lasts for more than 4 weeks. This has a significant impact on quality of life and overall health and can be disabling and even life-threatening in vulnerable groups such as infants, children and the elderly.

Diarrhoea and intestinal functioning
The colon, or large intestine, absorbs fluid from digested food particles that pass through it, forming semi-solid stools. If the intestinal lining becomes irritated, the intestinal tract either fails to reabsorb fluid effectively or promotes the secretion of intestinal fluid in the lumen, resulting in a watery stool.

The intestinal tract produces 10 litres of fluid  (acid, enzymes, bile, lubricants) to aid digestion daily. Eight litres are reabsorbed by the small intestine and the remainder reaches the colon where 1.9 litres are reabsorbed. Only 0.1 litres of fluid is excreted in the stools.Slow rhythmic contractions propel the digested food along, allowing the absorption of nutrients.

Diarrhoea is caused by rapid transit through the intestine which does not allow for re-absorption of liquid, inflammation of the intestines which does not allow for absorption of nutrients or liquid and finally by excessive secretion of fluid from the intestinal lining and the presence of osmotically active substances, including certain medications,  in the luminal tract.

Often more than one of these mechanisms are active when a person has diarrhoea. The inflamed intestinal lining itself may also leak excess fluid, adding to the water lost through diarrhoea. Diarrhoea has a positive effect in that it helps to rapidly expel dangerous microbes from the digestive tract.


There are many causes of diarrhoea, including food poisoning, infection, malabsorption and inflammatory disease of the gut. Diarrhoea is often caused by viral stomach flu or food poisoning. For most people diarrhoea is due to a self limiting infection or food poisoning which is resolved after a few days, and has no serious consequences. Diabetes Mellitus can also be a cause of chronic diarrhoea.

Infectious Diarrhoea

Infectious diarrhoea is caused by ingesting microscopic viruses, bacteria or parasites which then live in the intestine. These microbes are usually passed from the diarrhoea of others. Infections can be passed on by infected people who don’t wash their hands after bowel movements and having casual contact, such as preparing food. These intestinal disorders, characterised by inflammation of the mucous membrane, are often referred to as dysentery.

Virus infection is probably the most common cause of short-term diarrhoea. Usually these infections clear up by themselves. A virus, such as rotavirus or Norwalk, damages the mucous membrane lining the intestine, and disrupts fluid absorption. Rotavirus is often the cause of diarrhoea in children under two years old. Norwalk virus is more common in adults, and usually results from drinking contaminated water or food.

Bacteria in contaminated food or water produce toxins that trigger intestinal cells to secrete salt and water, resulting in diarrhoea. This is a type of food poisoning. Salmonella and Campylobacter are the most common types of bacterial infection. These serious conditions require medical evaluation. Traveller's diarrhoea is caused primarily by E. coli. It most often occurs in visitors to developing countries where sanitation is poor. Cholera, which has acute diarrhoea as one of its symptoms, is contracted mainly by drinking contaminated water.

Parasites such as amoeba and giardia can attack the intestine. Giardia may occur in wild animals and contaminated water. Giardiasis usually infects young children, often in day care, where it is transmitted by direct contact, or by adults changing different children’s nappies without hand washing in between. Family members of affected children are also at risk. Giardiasis can last months without treatment and spread rapidly. Finding the source and testing all contacts is important, as some people spread the infection without having diarrhoea themselves.

In addition to all the above-mentioned infections HIV positive individuals are also at risk of other opportunistic infections that can cause diarrhoea, e.g. cryptosporidium and isospora belli

Non-infectious Diarrhoea

Food: Certain foods may cause diarrhoea in some people. Many people are intolerant of the milk sugar lactose, due to lactase deficiency. This is an enzyme that breaks down lactose to glucose, which is then readily absorbed  by the intestinal tract. Even small amounts of milk or dairy products can cause diarrhoea in individuals with lactase deficiency. Large amounts of alcohol, caffeine, artificial sweetener, fatty or spicy foods cause diarrhoea in others.

A baby's digestive system may not tolerate large amounts of milk, juice or fruit. Breast-fed babies are less likely to develop diarrhoea, due to the presence of antibodies in breast milk.

Medications: If diarrhoea occurs after taking a new medicine, contact your doctor. Diarrhoea can also develop up to a month after taking antibiotics. Antibiotics change the gut microflora and can predispose to infection with a bacteria called Clostridium difficile, resulting in diarrhoea that can range in severity from a mild illness to life-threatening disease necessitating colectomy.

Many people become dependent on chemical laxatives such as Milk of Magnesia, magnesium sulphate (Epsom salts), cascara and phenolphthalein. Magnesium can be inadvertently ingested in certain over-the-counter products. Sorbitol, an artificial sweetener used in some products such as jams, is also a laxative.

Diseases: Chronic (i.e. > 2 weeks duration) diarrhoea can be caused by certain intestinal disorders, which include Irritable Bowel Syndrome, Inflammatory Bowel Diseases, including ulcerative colitis and Crohn's disease, chronic pancreatitis, coeliac disease, colon cancers and certain tumours of the small intestine. Microscopic colitis is an unusual condition which causes diarrhoea in elderly people. These are serious diseases requiring medical attention.

Irritable Bowel Syndrome (IBS) is a very common cause of diarrhoea and occurs when the intestine does not contract smoothly and rhythmically. The contractions can be too strong, causing diarrhoea, or too weak, causing constipation. There may be alternating constipation and diarrhoea. IBS is associated with abdominal pain and bloating, but no blood in the stool or loss of weight. Emotional stress may aggravate these symptoms.


Diarrhoea is a problem if there are frequent loose stools, including nocturnal stools, blood and mucus in the stools, associated vomiting and the person cannot rehydrate themselves adequately (usually the elderly and very young). Symptoms such as high fever, severe abdominal pain, diarrhoea that doesn’t improve after 48 hours are serious, and medical attention should be sought.

In babies and young children, normal stools may be watery or contain mucus. Each baby has different bowel habits. Many breast-fed babies have a bowel movement with each feeding and sometimes between feedings. Unless there is a change in a breast-fed baby's normal habits, loose, frequent stools are not considered to be diarrhoea. Formula-fed babies with lactose intolerance may have loose, greenish stools, or hard stools.

For babies and children, mild to moderate diarrhoea can be described as fewer than six large, loose stools in 12 hours. Diarrhoea can occur with other infections such as measles. As diarrhoea worsens babies become more irritable and restless. Their skin have reduced turgor and late signs include weakness, floppiness and seizures.

Diarrhoea is severe if a child under four years old has large stools every one to two hours. Severe diarrhoea causes the body to lose large amounts of fluid quickly, increasing dehydration risk. A child whose stools are always loose and very dark or foul-smelling should be medically examined. The mother should take her child to a health worker if the child starts to pass many watery stools, has repeated vomiting, becomes very thirsty,  is eating or drinking poorly, develops a fever, has blood in the stool, or does not get better within a period of three days.

Diarrhoea may be accompanied by other symptoms such as abdominal cramps, nausea and weakness:


  • Cramping (spasmodic) abdominal pain is common with diarrhoea. When it is relieved by passing gas or stool, such pain is rarely cause for concern. After passing several loose stools, the abdominal muscles may feel sore, but this type of pain should let up after diarrhoea stops. Continuous abdominal pain not relieved by passing gas or stool, or that localises to a specific part of the abdomen may indicate a more serious problem.
  • A young child with severe abdominal pain may clutch his stomach, scream, or pull his legs up to his chest. Severe abdominal pain that starts suddenly, continues, and is not relieved by passing stools may indicate a serious problem, such as bowel obstruction.
  • Many babies have cramping abdominal pain that makes them irritable (usually in the evening) for two to three months. This condition, colic, is often associated with diarrhoea.

Diarrhoea with nausea, vomiting, fever and aches, which persists for one to three days, may indicate viral gastroenteritis (stomach flu).

Diarrhoea with fever, chills and sometimes blood or mucus in the stool may indicate bacterial infection. Vomiting is less common.

Symptoms of food or lactose intolerance commonly include diarrhoea, bloating, gas and cramps a few hours after eating the offending foods. There will be no other signs of illness.

Diarrhoea with cramping during times of stress may be caused by emotional distress.

In children, viral and bacterial infections can cause diarrhoea, vomiting and high fever. A fever lasting up to four days is usually not a concern, especially if it comes and goes and gradually decreases.


Almost everyone gets diarrhoea occasionally and adults average four bouts a year. Diarrhoea is more common in developing countries and areas, and is a serious risk for babies and young children.


Usually diarrhoea lasts only a few days and isn't serious. However, severe or persistent diarrhoea, especially in babies, requires medical attention.

Risk factors for diarrhoea

  • Age:  Diarrhoea in children aged three or younger can be highly dangerous, as they are particularly vulnerable to dehydration. Newborns to two-month-old babies are at highest risk. Elderly patients are also vulnerable to dehydration.
  • Environment: Poor sanitation and hygiene
  • Medications:Antibiotics
  • Comorbidities: Diabetes, kidney disease, history of intussusceptions


Treatment of diarrhoea aims to eliminate the underlying cause (if the cause is known), firm up the bowel movements, and treat any diarrhoea-related complications.

General treatment of acute diarrhoea includes rest, encouragement of fluid intake, and taking of oral opiate-containing agents. Intravenous fluid and electrolyte replacement may be necessary in infants and elderly people. Oral sugar-electrolyte solutions may be prescribed in certain cases.

Home Treatment

The following methods may help reduce symptoms of mild diarrhoea:

  • Avoid solid food for a few hours until you feel better.
  • Avoid dehydration. Take frequent, small sips of water or a rehydration drink. Adults should drink about two cups of water an hour unless they are vomiting. Children older than two years can drink up to about 2.25 litres a day. Ask your doctor what to give a child under two years. Apart from water, you may choose liquids such as clear broth, caffeine-free soft drinks, weak tea with sugar, sports drinks, iced lollies, fruit juices (except apple and prune juice), jelly, or a mixture of four teaspoons of sugar and one teaspoon of salt with four cups of boiled water.
  • Avoid very hot or cold liquids.
  • Avoid apple juice and milk, these can worsen diarrhoea.
  • Avoid alcohol.
  • Most mild cases of diarrhoea don't require antibiotics or over-the-counter anti-diarrhoea products, such as Imodium. These may slow the elimination of the infectious agent, so avoid these products at least for the first six hours. Use them only if there are no other signs of illness, such as fever, and if discomfort continues.
  • If the diarrhoea was caused by an infection:
  • Wash your hands after using the toilet, and before handling food.
  • Dry your hands with paper towels and discard these.

In young children, oral rehydration solutions (ORSs) can be used to correct dehydration. ORSs contain the right balance of minerals and sugar to help replace body fluids. The amount of ORS taken depends on dehydration severity.

For babies to one-year-olds:

  • Don't wait until signs of dehydration develop to replace lost fluids.
  • Increase frequency of feedings. Give ORS between feedings if signs of dehydration develop. If the baby is vomiting, your doctor may suggest that you stop milk feeding and only give clear fluids.
  • The amount of ORS needed depends on the baby's weight and the degree of dehydration. Continue giving ORS until the baby's stools return to normal.
  • Give the baby a half-strength feed if you are bottle-feeding.
  • If your baby has started eating, you may replace lost fluids with foods such as cereal, strained bananas and mashed potatoes after each diarrhoea stool.
  • Nappy rash is common after diarrhoea. Protect the nappy area with zinc oxide or any other suitable cream.

For one to three-year-olds:

  • ORS, half-strength juice, or water (if the child is eating food) may be used to replace lost fluids. Offer the child half to one cup of fluid after each loose stool. The child should drink as much fluid as he or she wants. If diarrhoea persists or the child is dehydrated, use ORS as the main replacement fluid. Give ORS until stools return to normal. Other drinks do not contain the right mixture of minerals and sugar to replace lost fluids and may worsen the diarrhoea.
  • Do not withhold food. Give the child at least six small meals daily of easily digestible foods such as rice, pasta, bread, cooked beans or carrots, mashed potatoes and bananas. Salted biscuits can help replace salt lost from diarrhoea.
  • Avoid foods and drinks high in sugar, such as juice, soft drinks and sweets.
  • If the child drinks cow's milk, he or she may continue to do so.
  • Do not give the child prescription or non-prescription medicine to stop diarrhoea, unless so instructed by a doctor.

When the diarrhoea starts to improve:

  • Begin eating bland, mild foods, such as rice, dry toast or banana. Avoid other fruits, spicy and fatty foods, alcohol and coffee until 48 hours after symptoms disappear, and dairy products for three days after symptoms disappear.
  • Eat small amounts of soft foods like cooked potatoes. Avoid meat, nuts and beans. Avoid foods that are hard to digest, such as raw fruits and vegetables, fried foods and sweets, whole-grain bread or bran cereal. As symptoms improve, start to eat low-fibre foods, such as soda crackers, toast, eggs, rice, or chicken and other tender cuts of meat.
  • Even if you feel ravenous, try not to overeat. Eat small meals at regular intervals.
  • Don't exercise strenuously until you are free of symptoms.

Previously reviewed by Dr David Epstein (MBChB) (DCH.) (FCP (SA) Cert Gastroenterology), July 2009

Reviewed by Dr Naayil Rajabally MBBCh (Wits), FCP (SA), Cert Gastroenterology (Phys)Division of Gastroenterology, Department of Medicine, Groote Schuur HospitalLast updated, October 2011

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