Commonly known as the trots, the runs, skitters, rererere and runny tummy.

Diarrhoea is when your poos become runny or watery. You may need to go to the toilet often and with great urgency. It is usually more disruptive than dangerous and in most cases will clear up by itself within a few days.

Why does diarrhoea happen?

One of the important roles of the healthy bowel is to reabsorb water from your poo. With diarrhoea, the bowel is unable to do this. As a result, your poo becomes watery and excess fluid is lost from the body. This fluid loss can lead to dehydration.

People can become dehydrated very quickly if they do not drink enough fluids when they have diarrhoea, and children and elderly people are more at risk.

Seek immediate medical attention if:

What causes diarrhoea?

Diarrhoea is a symptom of other conditions or diseases – it is not a disease in itself. 

Diarrhoea is most often caused by a virus or bacterium in contaminated food or water (food poisoning), or a virus passed from person to person (gastroenteritis; this common problem can become serious in children).

Other causes of diarrhoea include rich food, too much alcohol, emotional stress, a reaction to medicines, or a food allergy or intolerance. Some long-term diseases can also cause diarrhoea.

What are the symptoms of diarrhoea?

Diarrhoea is experienced as watery bowel movements which may last a few days. You may also have painful stomach cramps, bloating, flatulence (wind), weakness, fever or vomiting. 

You should call your doctor if you also:

  • have blood or pus in your poo
  • have a fever above 39.5 ºC
  • have signs of dehydration (eg, thirst, dry mouth, lack of energy, passing less urine than normal, dizziness, confusion, or the skin on the back of the hand is slow to return to position after being pinched upwards)
  • have strong pain in your tummy or bottom
  • have a long-term medical condition (eg, diabetes needing insulin treatment or heart or kidney disease)
  • take certain medications, including the contraceptive pill (back-up methods are advised) or
  • have diarrhoea lasting more than two days.

Diarrhoea in children

If you have a baby aged under six months with diarrhoea, you should visit a doctor right away. Very young children can quickly become dehydrated and this can make them seriously unwell. 

Normally, when a tummy bug (like gastroenteritis) causes diarrhoea, you can expect your child to improve after a couple of days. You should visit your doctor if you have a child aged over six months who:

  • has a lot of diarrhoea (eight to 10 watery bowel motions, or two or three large motions per day)
  • is unable to keep fluids down
  • develops severe stomach pains, or
  • shows signs of dehydration.

What is the treatment for diarrhoea?

Drink lots of fluids

If you have diarrhoea, the most important treatment is to keep your fluid intake up. Try to drink small amounts of water often. Oral rehydration solutions (available from pharmacies) are useful because they also replace vital salts. Avoid fizzy or sugary drinks (including fruit juice) and milk. 

For 48 hours, try to eat bland, non-greasy foods or soups and avoid grains, uncooked fruits and vegetables, and alcohol. 


Antimotility medicines slow the movement (motility) of your gut and can help reduce any cramps and the frequency of toilet visits. The slowing down of motility may also help the body to absorb fluid. These medicines do not cure the cause of the diarrhoea. 

If the diarrhoea symptoms do not improve within 48 hours of using these medicines, see your doctor. They may require a stool sample to run some tests on. If these tests reveal the problem is caused by a particular type of bacterium or parasite, your doctor may prescribe a course of antibiotics.

Caring for children with diarrhoea

Making sure your child is drinking enough fluids is the main form of treatment. Offer them small amounts of fluid often (aim for about one-quarter of a cup every 15 minutes). Keep offering your child fluids even if they are vomiting.

Which fluids should I give my child?

  • If you are breastfeeding, continue this. You may need to feed more often and you may need to give extra fluid.
  • An electrolyte and fluid replacement solution is good to give your child when they are dehydrated – you can buy these child formulations from a pharmacy.
  • Milk formula at normal strength, or cows’ milk if the child is over one-year-old.
  • Clear, thin soups or flat, diluted lemonade (one part to five parts warm water).

Do NOT give undiluted soft drinks, fruit juice, sports drinks, Lucozade and Ribena, as too much sugar increases the diarrhoea and dehydration.

What foods can I give my child?

Children should be offered food if they are hungry (even if diarrhoea continues). Your child may refuse food at first – this is not a problem as long as fluids are taken. If possible, do not stop food for more than 24 hours. 

Avoid high sugar or fatty foods. Try giving foods such as bread/toast, rice, porridge, milk pudding, yoghurt.

Can I give my child antimotility medications?

Do not give a child medicines to reduce diarrhoea – they may be harmful to children. See your doctor if you are concerned about your child's symptoms. 

Learn more

Plunketline – phone 0800 933 922 – for information and advice on parenting and health issues for children under five years.
Healthline – phone 0800 611 116 – for advice about health concerns for people of all ages.

Both numbers are staffed 24 hours a day by registered nurses or other health professionals. Calls to either line (within New Zealand) are free and confidential.

Credits: Health Navigator Editorial Team, April 2014.