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What causes diarrhoea?

Diarrhoea usually occurs when fluid cannot be absorbed from your bowel contents, or when extra fluid leaks into the bowel, causing watery stools (poo).

Conditions causing acute diarrhoea

Diarrhoea is usually a symptom of gastroenteritis, an infection of the bowel. Gastroenteritis may be caused by:

  • a virus, such as norovirus or rotavirus
  • bacteria, such as campylobacter, Clostridium difficile (C. difficile), Escherichia coli (E. coli), salmonella and shigella – these may all cause food poisoning
  • parasites, such as the Giardia intestinalis parasite that causes giardiasis and can come from contaminated water sources.

Diarrhoea caused by contaminated food or water from a foreign country is known as 'traveller's diarrhoea'.

Other causes of acute diarrhoea

Other short-term causes of diarrhoea include:

  • food poisoning (due to eating something contaminated or ‘off’)
  • emotional upset or anxiety
  • drinking too much alcohol
  • drinking too much coffee
  • food allergy
  • appendicitis
  • damage to the lining of the intestines due to radiotherapy or prescribed medications
  • damage to the intestines due to reduced blood supply, for example, because of a hernia.

Check your symptoms with healthdirect’s Symptom Checker to get advice on when to seek medical attention.

Conditions causing persistent (chronic) diarrhoea

Persistent or chronic diarrhoea is diarrhoea that has lasted longer than 4 weeks.

Conditions that can cause persistent diarrhoea include:

  • irritable bowel syndrome – a poorly understood condition where the normal functions of the bowel are disrupted
  • coeliac disease – a digestive condition where you are intolerant to the protein gluten
  • Chrohn's disease – a condition that causes inflammation of the lining of the digestive system
  • cystic fibrosis – an inherited condition that affects the lungs and digestive system
  • diabetes – a condition where there is too much glucose in the blood
  • diverticular disease – when small pouches (diverticula) form in the large intestine, causing symptoms such as diarrhoea
  • gastrectomy – a surgical procedure to remove part of the stomach, for example, to treat stomach cancer
  • lactose intolerance – lactose is a natural sugar that is found in milk
  • microscopic colitis – a type of inflammatory bowel disease that causes watery diarrhoea
  • chronic pancreatitis – inflammation of the pancreas, a small organ that produces hormones and digestive juices
  • ulcerative colitis – a condition that affects the colon (large intestine)
  • bowel cancer – cancer in the bowel can cause diarrhoea and blood in your stools.

If you have chronic or persistent diarrhoea see your doctor so it can be investigated.

Diarrhoea caused by medicines

Diarrhoea can also be a side effect of many different medicines, including:

  • antibiotics
  • antacid medicines that contain magnesium
  • some medicines used in chemotherapy
  • non-steroidal anti-inflammatory drugs
  • selective serotonin reuptake inhibitors
  • some antidepressants
  • statins (cholesterol-lowering medicines)
  • laxatives – a type of medicine that can help you empty your bowels if you are having trouble going to the toilet.

The consumer medicines information leaflet that comes with your medicine should state whether diarrhoea is a possible side effect. Or you can contact the Medicines Line on 1300 633 424 a national information service, that provides Australians with information about their medicines over the phone, Monday to Friday, 9am to 5pm EST. If you need an interpreter, you can ring the Translating and Interpreting Service (TIS National) on 131 450

Not sure what to do next?

If you are still concerned about your diarrhoea, check your symptoms with healthdirect’s online Symptom Checker to get advice on when to seek medical attention.

The Symptom Checker guides you to the next appropriate healthcare steps, whether it’s self care, talking to a health professional, going to a hospital or calling triple zero (000).

Last reviewed: July 2015

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