Diarrhoea can be caused by viruses, bacterial infections, food poisoning or side-effects of medications, including antibiotics.
Gastroenteritis (infection of the intestine), causing diarrhoea with or without vomiting, affects about 20 per cent of the UK population every year. Norovirus (the so-called winter vomiting bug) can lead to diarrhoea, with up to a million people in the UK catching it annually.
Food poisoning can be caused by bacterial contamination of food. The bugs to blame include salmonella, campylobacter and E. coli.
A longer-term common cause of diarrhoea is irritable bowel syndrome (IBS), a collection of gut symptoms which also include constipation, bloating and cramping pains.
Other longer-term causes include: inflammatory bowel disease (IBD), an autoimmune condition where antibodies attack the lining of the gut; coeliac disease, where the body produces antibodies to gluten (a protein found in wheat, barley and rye); and bile acid absorption, where the body doesn't recycle enough bile acid and produces watery diarrhoea.
Diarrhoea can be a symptom of bowel cancer, particularly if it's a new symptom and you're over 50; other symptoms include blood in the stools and lower abdominal pain or bloating.
Diarrhoea causes frequent bowel movements (more than three times a day) and soft or watery stools. It can also cause stomach pains, nausea, loss of appetite, fever, and dehydration. In rare cases, damage to the bowel or digestive tract can lead to blood in the stools.
Most cases will clear up on their own within two to four days (up to seven for children), but if your symptoms carry on beyond this, you have severe and ongoing pain, or experience blood in your stools, you should visit a doctor for further investigation.
Your doctor may also take a stool sample and perform blood tests. These will show what bacteria is causing your diarrhoea or in some cases give clues to what underlying condition may be to blame. Where a more serious underlying cause is suspected, such as inflammatory bowel, disease you should be referred to a gastroenterologist.
Who gets it?
Diarrhoea affects everyone. Stomach bugs, for instance the norovirus and the rotavirus in children, are extremely common, as is eating food contaminated with bacteria such as salmonella.
Travelling to other countries can increase your risk of diarrhoea as your body is exposed to different food, environments and toxins. Because of this, it usually happens within the first week. The majority of cases of 'travellers' diarrhoea' are mild, but about three per cent have 10 or more trips to the toilet a day. The best way to avoid this is to drink bottled water, wash your hands regularly and, if possible, carry antibacterial gel or wipes.
About a third of people with IBS have a form called IBS-D (IBS where diarrhoea is the predominant symptom) that causes watery stools in over 25 per cent of bowel movements.
Cancer treatment, including chemotherapy and radiotherapy, can also damage the digestive tract and therefore increase your chances of diarrhoea.
Treatment for acute diarrhoea (after a stomach bug or food poisoning) includes keeping fluids topped up, using rehydration salts and taking the anti-diarrhoea medication loperamide, which slows down muscle contractions in the gut so more water is absorbed from stools and they become firmer. Alcohol, fried food, dairy, and sugary drinks can all make your symptoms worse. Not only can they aggravate your digestive tract further, but some of these can make you even more dehydrated.
Take special care with children and the elderly who can become dehydrated very quickly. For mild to moderate dehydration in children, it's recommended to give small amounts of rehydration solution regularly over a four-hour period. In severe cases of dehydration, you may have to be admitted to hospital for rehydration on a drip.
Zinc supplements have been found to reduce stool volume by up to 30 per cent as well as cutting the duration of diarrhoea episodes by a quarter.
If your diarrhoea is caused by IBS, you might be asked to keep a food diary to help identify which foods are more likely to trigger your symptoms. If coeliac disease is suspected, you may be tested and if diagnosed, told to avoid eating foods containing gluten.
A number of studies have found the probiotic Saccharomyces boulardii (S.boulardii) is both a safe and effective way to treat and prevent gastrointestinal problems, including diarrhoea.