Increased fluidity, frequency, or volume of bowel movements. It may be acute or chronic. Diarrhoea can be very serious in infants and elderly people because of the risk of severe, potentially fatal, dehydration. Acute diarrhoea is usually a result of consuming food or water contaminated with certain bacteria or viruses (see food poisoning). Infective gastroenteritis also causes diarrhoea and may be acquired as a result of droplet infection. Other causes of acute diarrhoea include anxiety and, less commonly, amoebiasis, shigellosis, typhoid fever and paratyphoid fever, drug toxicity, food allergy, and food intolerance. Chronic diarrhoea is generally repeated attacks of acute diarrhoea. It may be the result of an intestinal disorder such as Crohn’s disease, ulcerative colitis, cancer of the colon (see colon, cancer of), or irritable bowel syndrome. Diarrhoea that recurs, persists for more than a week, or is accompanied by blood requires medical investigation. The water and electrolytes (salts) lost during a severe attack of diarrhoea need to be replaced to prevent dehydration. Ready-prepared powders of electrolyte mixtures can be bought (see rehydration therapy). Antidiarrhoeal drugs, such as diphenoxylate and loperamide, should not be taken to treat attacks of diarrhoea due to infection; they may prolong it. Drugs may help if the diarrhoea is disabling or if there is abdominal pain. Viral gastroenteritis in a child can damage the lining of the intestine, which may lead to lactose intolerance and further diarrhoea. Seek medical attention if diarrhoea in an infant persists for more than 48 hours. Call a doctor urgently if the infant is dehydrated. (See also rehydration therapy.)


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