Diarrhoea

What causes acute diarrhoea?

Infection of the gut

This is the most common cause. This is of sudden onset and is called acute infectious diarrhoea:

• Gastroenteritis. Many bacteria, viruses and other germs can cause diarrhoea. Sometimes the germs come from infected food (food poisoning). Infected water is a cause in some countries. Sometimes it is just 'one of those germs going about'.

• Viruses are easily spread from one person to another by close contact, or when an infected person prepares food for others.

• Examples of infectious diarrhoea include norovirus, Clostridioides difficile, Escherichia coli, campylobacter, salmonella and cryptosporidium.

Other causes

Other causes that are uncommon include drinking lots of beer, side-effects from some medicines and anxiety.

Gut disorders

Gut disorders that cause persistent (chronic) diarrhoea may be mistaken for acute diarrhoea when they first begin - for example, diarrhoea caused by ulcerative colitis.

The rest of this leaflet deals only with infectious causes of acute diarrhoea. There are also other leaflets that give more details about some of the different germs (microbes) that cause infectious diarrhoea. See also the separate leaflet called Acute Diarrhoea in Children.

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Bile acid diarrhoea

Bile acid diarrhoea is common, especially in people who are thought to have irritable bowel syndrome. Bile acid diarrhoea may be caused by a problem with the bowel. Much more often there is no medical problem causing the diarrhoea. Bile acid diarrhoea responds very well to treatment with a medicine called a bile acid binder. The outcome is usually very good if there is no other problem with the bowel.

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What are the symptoms of diarrhoea?

Diarrhoea is, itself, a symptom. It means loose or watery poo and frequent bowel movements (typically occurring at least three times a day). Other symptoms that can appear alongside diarrhoea, particularly with acute infectious diarrhoea, include:

• Being sick (vomiting).

• Blood or mucus can appear in the stools with some infections.

• Crampy pains in your tummy (abdomen) are common. Pains may ease for a while each time you pass some diarrhoea.

• A high temperature (fever).

• Headache

• Aching limbs.

If vomiting occurs, it often lasts only a day or so but sometimes longer. Diarrhoea often continues after the vomiting stops and commonly lasts for several days or more. Slightly loose stools may persist for a week or so further before a normal pattern returns. Sometimes the symptoms last longer.

Symptoms of lack of fluid in the body (dehydration)

Diarrhoea and vomiting may cause dehydration and they need rapid medical attention. Severe dehydration is more common in babies and is a medical emergency. Read about symptoms to look out for in the Gastroenteritis leaflet. For symptoms to look out for, read the separate Gastroenteritis leaflet.

How long does diarrhoea last?

If diarrhoea is due to an acute infection (gastroenteritis), it usually stops within five to seven days, although sometimes it can take a week or two to settle. Diarrhoea that lasts longer than two weeks could suggest another cause, like an infection that hasn't cleared, or another gut problem.

How to treat diarrhoea

Symptoms often settle within a few days or so as your immune system usually clears the infection. Rarely, admission to hospital is needed if symptoms are severe, or if complications develop (see below).

The following diarrhoea treatments are commonly advised until symptoms ease.

Drink lots of water

The aim is to prevent lack of fluid in the body (dehydration), or to replace lost fluids in the body. (Note: if you suspect that you are dehydrated, you should contact a doctor.)

• As a rough guide, drink at least 200 mls after each bout of diarrhoea (after each watery stool (faeces).

• This extra fluid is in addition to what you would normally drink. For example, an adult will normally drink about two litres a day but more in hot countries. The above advice of 200 mls after each bout of diarrhoea is in addition to this usual amount that you would drink.

• If you have been sick (vomited), wait 5-10 minutes and then start drinking again but more slowly. For example, a sip every 2-3 minutes but making sure that your total intake is as described above.

• You will need to drink even more if you are dehydrated. A doctor will advise on how much to drink if you are dehydrated.

For most adults, fluids drunk to keep hydrated should mainly be water. It is best not to have drinks that contain a lot of sugar, such as cola or pop, as they can sometimes make diarrhoea worse.

Rehydration drinks

Rehydration drinks are recommended for people who are frail, or over the age of 60, or who have underlying health problems. They are made from sachets that you can buy from pharmacies (eg, Dioralyte®). (The sachets are also available on prescription.) You add the contents of the sachet to water.

Rehydration drinks provide a good balance of water, salts and sugar. They do not stop or reduce diarrhoea. However, the small amount of sugar and salt helps the water to be absorbed better from the gut into the body.

In children with gastroenteritis, diluted fruit juice (especially apple juice) can be useful, and may be as good as rehydration drinks in some cases. Apple juice should be diluted 50:50 with water. Children often prefer the taste of this to water or rehydration drinks, and so it can be easier to get them to take small amounts regularly.

Salt/sugar mixtures

Home-made salt/sugar mixtures are used in developing countries if rehydration drinks are not available but they have to be made carefully, as too much salt can be dangerous. Rehydration drinks are cheap and readily available in the UK and are the best treatment.

Anti-secretory medicines

These are designed to be used with rehydration treatment. They reduce the amount of water that is released into the gut during an episode of diarrhoea. They can be used for young children who are older than 3 months of age, and for adults.

Eat as normally as possible

It used to be advised to not eat for a while if you had infectious diarrhoea. However, now it is advised to eat small, light meals if you can. Be guided by your appetite. You may not feel like food and most adults can do without food for a few days.

Eat as soon as you are able - but don't stop drinking. If you do feel like eating, avoid fatty, spicy or heavy food at first. Plain foods such as wholemeal bread and rice are good foods to try eating first.

Medication

Antidiarrhoeal medicines are not usually necessary. See the separate leaflet called Diarrhoea Medicine for further information.

Can diarrhoea be prevented?

Diarrhoea can't always be prevented, but you can reduce your risk greatly with simple hygiene measures. You can find out more in the separate leaflet called Gastroenteritis.

Preventing spread of infection to others

Some infections causing diarrhoea are very easily passed on from person to person. If you have acute diarrhoea, the following are also recommended to prevent the spread of infection to others:

• Wash your hands thoroughly after going to the toilet. Ideally, use liquid soap in warm running water but any soap is better than none. Dry properly after washing.

• Don't share towels and flannels.

• Don't serve or prepare food for others.

• Regularly clean the toilets that you use. Wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles with hot water and detergent at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).

• Stay off work, college, etc, until at least 48 hours after the last episode of diarrhoea or being sick (vomiting).

• Food handlers: if you work with food and develop diarrhoea or vomiting, you must immediately leave the food-handling area. For most, no other measures are needed, other than staying away from work until at least 48 hours after the last episode of diarrhoea or vomiting. Some special situations may arise and sometimes longer time off is needed. Specialist advice may be needed for some uncommon causes of infectious diarrhoea. If in doubt, seek advice from your employer or GP.

• If the cause of acute diarrhoea is known to be (or suspected to be) a germ called Cryptosporidium spp., you should not swim in swimming pools for two weeks after the last episode of diarrhoea.

Are there any complications that may occur from diarrhoea?

Complications are uncommon in the UK. They are more likely in the very young, in pregnant women, or in the elderly. They are also more likely if you have an ongoing (chronic) disease such as diabetes, or if your immune system may not be working fully. For example, if you are taking long-term steroid medication or you are having chemotherapy treatment for cancer.

Possible complications include the following:

Lack of fluid (dehydration) and salt (electrolyte) imbalance in your body

See the leaflet on gastroenteritis for more details.

Reactive complications

Rarely, other parts of the body may react to an infection that occurs in the gut. This can cause symptoms such as joint inflammation (arthritis), skin inflammation and eye inflammation (either conjunctivitis or uveitis). Reactive complications are uncommon if you have a virus causing infectious diarrhoea.

Spread of infection

The infection can spread to other parts of your body such as your bones, joints, or the meninges that surround your brain and spinal cord. This is rare. If it does occur, it is more likely if diarrhoea is caused by Salmonella spp. infection.

Persistent syndromes of diarrhoea

This rarely develops.

Irritable bowel syndrome (IBS)

IBS is sometimes triggered by a bout of infectious diarrhoea.

Lactose intolerance can sometimes occur

Lactose intolerance can sometimes occur for a period of time after infectious diarrhoea. This is known as secondary or acquired lactose intolerance. Your gut lining can be damaged by the episode of diarrhoea. This leads to lack of an enzyme (chemical) called lactase that is needed to help your body digest a sugar called lactose that is in milk.

Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the gut lining heals. It is more common in children.

Haemolytic uraemic syndrome

This is another potential complication. It is rare and is usually associated with infectious diarrhoea caused by a certain type of Escherichia coli infection. It is a serious condition where there is anaemia, a low platelet count in the blood and kidney failure. It is more common in children. If recognised and treated, most people recover well.

Reduced effectiveness of some medicines

During an episode of infectious diarrhoea, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because the diarrhoea and/or vomiting means that reduced amounts of the medicines are taken up (absorbed) into your body.

Examples of such medicines are medicines for epilepsy, diabetes and contraception. Speak to your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have acute diarrhoea.

Do I need any tests for diarrhoea?

Most people with diarrhoea do not need to see a doctor or seek medical advice. Symptoms are often quite mild and commonly get better within a few days without any medical treatment.

However, in some circumstances, you may need to see a doctor (see below about when to seek medical advice). The doctor may ask you various questions - for example, about:

• Recent travel abroad.

• Whether you have been in contact with someone with similar symptoms.

• Whether you have recently taken antibiotics.

• Whether you have recently been admitted to hospital.

This is to look for possible causes of your diarrhoea. The doctor will also usually examine you, especially looking for signs of dehydration.

Tests are not usually needed. However, if you are particularly unwell, have bloody stools (faeces), have recently travelled abroad, are admitted to hospital, or your symptoms are not getting better, your doctor may ask you to collect a stool sample. This can then be examined in the laboratory to look for the cause of the infection.

When should I seek medical advice?

Seek medical advice in any of the following situations, or if any other symptoms occur that you are concerned about:

• If you suspect that you are becoming lacking in fluid in the body (dehydrated).

• If you are being sick (vomiting) a lot and unable to keep fluids down.

• If you have blood in your diarrhoea or vomit.

• If you have severe tummy (abdominal) pain.

• If you have severe symptoms, or if you feel that your condition is becoming worse.

• If you have a persisting high temperature (fever).

• If your symptoms are not settling - for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days.

• Infections caught abroad.

• If you are elderly or have an underlying health problem such as diabetes, epilepsy, inflammatory bowel disease (IBD), kidney disease.

• If you have a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, HIV infection.

• If you are pregnant.