The passage of loose or watery stools and/or an increase in the frequency of bowel movements

  • Poor food hygiene is a risk factor
  • Age, gender, and genetics are not significant factors

Diarrhoea is the production of stools that are more watery, more frequent, or greater in volume than is normal for a particular individual. Although it is not a disease in itself, diarrhoea may be a symptom of an underlying disorder.

In some cases, diarrhoea is accompanied by abdominal pain, bloating, loss of appetite, and vomiting. Severe diarrhoea can also lead to dehydration that may be life-threatening, particularly in babies (see Vomiting and diarrhoea) and elderly people.

Short bouts of diarrhoea, especially if they are associated with vomiting, are often due to gastroenteritis or food poisoning. Diarrhoea that lasts more than 3–4 weeks usually indicates that there is an intestinal disorder and requires medical attention.

What are the causes?

Diarrhoea that starts abruptly in a person who is otherwise healthy is often caused by contaminated food or water and may last a few hours to 10 days. This sort of diarrhoea often occurs during travel in a developing country, where food hygiene and sanitation may be poor. Diarrhoea can also be caused by a viral infection that is spread by close personal contact. For example, infectious gastroenteritis is a common cause of diarrhoea in babies and young children.

People with reduced immunity, such as those with AIDS (see HIV infection and AIDS), are more susceptible to infectious gastroenteritis, which also tends to be more severe in these people. People taking drugs such as antibiotics may develop sudden diarrhoea if the drugs disturb the normal balance of bacteria in the colon.

Persistent diarrhoea may result from long-standing inflammation of the intestine due to disorders such as ulcerative colitis or Crohn’s disease or some conditions in which the small intestine is unable to absorb nutrients (see Malabsorption). Lactose intolerance, a disorder in which lactose (a natural sugar present in milk) cannot be broken down and absorbed, can also cause diarrhoea.

Infections with protozoal parasites, such as giardiasis and amoebiasis, can cause persistent diarrhoea. Irritable bowel syndrome may produce abnormal contractions of the intestine, which result in alternating episodes of diarrhoea and constipation.

What might be done?

In most cases, diarrhoea clears up after a day or two. Other symptoms that can accompany diarrhoea, such as headache, weakness, and lethargy, are most often caused by dehydration. The symptoms of dehydration disappear as soon as lost fluids and salts are replaced (see Preventing dehydration).

If your diarrhoea lasts longer than 3–4 days, you should consult your doctor, who may request a sample of faeces to look for evidence of infection. If the diarrhoea persists for more than 3–4 weeks or if there is blood in the faeces, your doctor will probably arrange for you to have investigations, such as contrast X-rays of the intestines, sigmoidoscopy, or colonoscopy.

Specific treatments given for diarrhoea depend on the underlying cause. If you need to relieve your diarrhoea quickly, your doctor may prescribe an antidiarrhoeal drug, such as loperamide. However, antidiarrhoeal drugs should be avoided if your diarrhoea is due to an infection because they may prolong the infection. Antibiotics are only needed to treat persistent diarrhoea that has a known bacterial cause.

Self-help: Preventing Dehydration

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

Back to top