Diarrhoea is when your bowel movements become loose or watery. The definition of diarrhoea is passing loose or watery bowel movements 3 or more times in a day (or more frequently than usual).
Diarrhoea occurs when the lining of the intestine is unable to absorb fluid, or it actively secretes fluid. There are many causes, including infection and inflammation.
Many cases of diarrhoea are self-limiting and don’t need specific treatment. However, it’s important in any case of diarrhoea to stay hydrated by drinking plenty of liquids.
Symptoms of diarrhoea
In addition to frequent, watery bowel movements, the stool may also contain mucus, pus, blood or excessive amounts of fat.
Diarrhoea can be accompanied by:
- painful abdominal cramps;
- bloating; and
- generalised weakness.
Diarrhoea can cause dehydration, especially in young children and older people. Symptoms of dehydration in adults can include:
- lack of energy;
- passing less urine than normal;
- dizziness or light-headedness; and
- the skin on the back of your hand being slow to return to position after being pinched upwards.
Symptoms of mild to moderate dehydration in children can include:
- dry mouth;
- passing less urine than usual (often noticed as fewer wet nappies in babies and toddlers);
- listlessness; and
- less tears when crying.
Signs of severe dehydration in children include sunken eyes, cheeks or belly, or a sunken fontanelle (the soft spot on the top of the head in babies and toddlers).
People with diarrhoea, especially the very young and the very elderly, are at risk of becoming rapidly dehydrated. This requires immediate medical attention.
Diarrhoea may have many different causes including the following.
- Infection (with a virus, bacteria or parasite). Infectious diarrhoea is most commonly caused by viruses passed from person to person, or by eating or drinking food or water contaminated with viruses, bacteria – such as Salmonella, or a parasite – such as Cryptosporidium.
- A change in diet.
- Food intolerance (e.g. lactose intolerance). Some people have diarrhoea after eating foods containing fructose (a type of sugar) or artificial sweeteners such as sorbitol and mannitol.
- Drinking excess alcohol.
- Bowel conditions such as inflammatory bowel disease (ulcerative colitis or Crohn’s disease), coeliac disease or irritable bowel syndrome (IBS).
- Malabsorption (e.g. due to problems with the pancreas).
- Surgery (e.g. when part of the bowel has been removed).
- Some medicines can cause diarrhoea as a side effect. Antibiotics are a common example. They can disrupt the balance of bacteria in your gut, which can lead to diarrhoea. Other examples of medicines that can cause diarrhoea include some antacids and diabetes tablets.
Diarrhoea in very young children is often caused by viral infections. Rotavirus infections were a common cause, but this risk is reduced by the rotavirus vaccine, which can prevent gastroenteritis (or reduce the risk of severe gastroenteritis) caused by rotavirus infection. Many other viruses still commonly cause diarrhoea in infants and toddlers.
When to see your doctor about diarrhoea
Most people have experienced an episode of diarrhoea at some time in their lives. Generally, this resolves after a few days.
You should seek medical advice if:
- A child or elderly person has severe diarrhoea, as they may become rapidly dehydrated.
- Diarrhoea lasts more than 5 days in an otherwise healthy adult.
- Your diarrhoea has not improved with self-care measures.
- There is bright red blood in the faeces, or stools are dark and tarry.
- You have diarrhoea that contains mucus.
- The faeces have high fat content, which may be seen as pale, greasy, foul smelling stools that are difficult to flush.
- Symptoms include fever, rash or stomach cramps, or a general feeling of being unwell.
- You have vomiting, weakness and dizziness.
- You have associated weight loss.
- You have symptoms of dehydration (thirst, lack of energy, passing less urine than normal, dizziness or the skin on the back of your hand being slow to return to position after being pinched upwards).
- Constipation alternates with the diarrhoea.
- The diarrhoea was acquired while travelling overseas.
- The diarrhoea is associated with use of a medication and is not improving.
- If you have a pre-existing medical condition such as type 1 diabetes, heart failure or kidney failure.
If your child has diarrhoea, take them to a doctor straight away if they have:
- symptoms of dehydration;
- diarrhoea lasting for more than 48 hours;
- vomiting that is stopping them from keeping down fluids;
- blood or pus in their stool;
- an associated rash;
- a fever above 38 degrees Celsius;
- severe pain in their abdomen; or if
- they are lethargic, cool, floppy, pale or unwell looking.
Diagnosis and tests
Your GP (general practitioner) will ask about your symptoms and how long you have had diarrhoea and ask about your diet and any medicines you are taking. They will want to examine you, looking for signs of dehydration and possible causes of diarrhoea.
Your doctor may recommend sending a stool sample to a laboratory for testing. Blood tests may also be recommended.
Depending on your symptoms, your doctor may refer you to a gastroenterologist (specialist in conditions of the digestive tract) for further evaluation and tests.
Most adults will experience diarrhoea at some time. Most people do not need any specific treatment for infectious diarrhoea as it usually improves on its own in a couple of days. However, it is important to drink plenty of liquids to keep well hydrated. This is especially important for children and babies.
The treatment for non-infectious diarrhoea will depend on the cause.
If you have diarrhoea you should drink plenty of fluids. Suitable fluids include:
- Water. However, if dehydration is sufficiently severe, water alone is inadequate.
- Oral rehydration fluids (available from pharmacies) contain not only the water replacement that is required in diarrhoea or vomiting-induced dehydration, but also important electrolytes that must be replaced. Available products include Gastrolyte, Hydralyte, Pedialyte and Repalyte. These should be mixed exactly to the manufacturer’s directions. It is very important to comply with the expiry dates of the rehydration solutions once they have been opened or made up.
- Diluted cordial (one part cordial concentrate to 20 parts water).
- Diluted soft drink or juice (one part juice or soft drink to 5 parts water).
Do not drink undiluted lemonade or other undiluted soft drinks, as the high glucose content may draw fluid into the gut, causing more diarrhoea. Also, do not use sports rehydration drinks.
If you have nausea, try taking small sips of fluid often. Even if you vomit after drinking, you will likely absorb some fluid. If you don’t drink you will only get more dehydrated.
Severe dehydration needs to be treated in hospital with intravenous fluids (fluids given into a vein, via a drip).
Restrict your food intake if you have gastroenteritis with vomiting. However, do not limit fluid intake.
While you have diarrhoea, avoid caffeine (tea, coffee, cola drinks), alcohol and foods that are fatty, very sweet or high in fibre. Dairy products may aggravate symptoms, but yoghurt (which contains less lactose than milk) may be tolerated.
Resume eating solid food slowly and choose foods that are bland, low in fat and low in fibre. This includes crackers, boiled potatoes, plain rice, or toast. Restrict consumption of fatty, sweet or spicy foods for 48 hours.
Some people may experience lactose intolerance (inability to digest milk sugars) for some time after the diarrhoea has settled. If this persists beyond a week or 2 you should seek medical assistance.
Anti-motility medicines (sometimes called anti-diarrhoeal medicines) can help slow down the diarrhoea. These medicines may be useful in relieving symptoms of mild or moderate diarrhoea if short term control is needed, for example during travel. These medicines can be obtained from pharmacies.
Anti-motility medicines should not be used if you have severe or bloody diarrhoea and may be dangerous in this instance. They should never be used to treat diarrhoea in infants and children.
Available products include:
- loperamide (e.g. Gastro-Stop, Imodium, Stop-It); and
- diphenoxylate and atropine (e.g. Lomotil, Lofenoxal).
These medicines may worsen bacteria-induced diarrhoea, and may cause drowsiness. Alcohol should be avoided.
Antibiotics are prescribed only in some cases of diarrhoea that is caused by bacteria or parasites. Your doctor may request a stool sample to test for bacteria or parasites before starting antibiotic treatment.
If you’ve had an episode of gastroenteritis, you may benefit from taking probiotics.
Diarrhoea and your medicines
Diarrhoea can affect the way that some medicines (such as the contraceptive pill) are absorbed. If you take the contraceptive pill and develop diarrhoea, you should use a back-up method of contraception, such as condoms, until your next menstrual period because the diarrhoea may make the pill less effective.
If you are taking any other regular medicine, talk to your doctor about the effects that diarrhoea may have had on its effectiveness.
Some types of diarrhoea can very easily be passed on. It is important that children do not go to school or childcare when they have diarrhoea.
Likewise do not prepare food for people if you are suffering from diarrhoea. You may go on being infectious for a time after you feel better, so keep strict food hygiene precautions for a week after any diarrhoeal illness.
Wash your hands thoroughly with warm water and soap after going to the toilet and before food preparation — teach your children to do the same. Hand sanitisers are useful when you are not near a sink.
There is a vaccine available that can prevent gastroenteritis (or reduce the risk of severe gastroenteritis) caused by rotavirus infection. Rotavirus vaccine is given as part of the routine childhood immunisation schedule.