Diarrhoea happens when not enough water is removed from your stool, or too much fluid is secreted into the stool, making it loose. There are many different causes of diarrhoea. It can be caused by a short-term illness that clears up in a few days, or it may be a symptom of an ongoing problem or chronic condition. Short-term causes of diarrhoea Short-term diarrhoea is often due to infections, such as: viral gastroenteritis — for example, caused by rotavirus or norovirus-infection waterborne parasites, such as cryptosporidium and giardia bacteria that cause food poisoning, such as clostridium, salmonella, E. coli and campylobacter bacteria Other causes of short-term diarrhoea include: change in diet certain food ingredients, for example the artificial sweeteners sorbitol and mannitol, and the natural sugar fructose drinking too much alcohol stress Long-term causes of diarrhoea Diarrhoea can be caused by some long-term conditions, such as: inflammatory bowel disease (Crohn’s disease and ulcerative colitis) irritable bowel syndrome food intolerances, such as lactose intolerance diverticulitis malabsorption syndromes — for example, after bowel surgery encopresis / chronic constipation — where diarrhoea overflows around impacted stool stuck in the bowel People who are immunosuppressed or have weakened immune systems, such as those living with cancer, HIV/AIDS or who have had an organ transplant, are more likely to develop ongoing diarrhoea as a result of a bout of gastroenteritis. Treatments which can cause diarrhoea Some medical treatments may cause diarrhoea as a side effect: some medicines — for example, antibiotics laxatives, if too many are taken radiotherapy involving the abdomen or pelvis chemotherapy More information is available about specific causes of diarrhoea and their symptoms.