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Diarrhoea (gastroenteritis)

What is diarrhoea?

Diarrhoea is when your bowel movements (faeces) become more runny or watery; you may also need to go to the toilet frequently and urgently, and the faeces can have an offensive smell. You may also have painful stomach cramps, bloating, flatulence (wind), weakness, fever or vomiting. Some common names for diarrhoea are the 'trots', the 'runs', 'skitters', 'rererere', and 'tummy bug'.

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.

Is diarrhoea dangerous?

One of the important roles of the healthy bowel is to reabsorb water from the faeces. With diarrhoea, the bowel is unable to do this, hence the watery bowel movements. This fluid loss can cause the body to become dehydrated – this can happen quickly and is a serious problem if not attended to, particularly in the elderly and the very young.
If you have a baby aged under six months with diarrhoea, you should visit a doctor right away
. The younger the child, the easier it is for them to become dehydrated.

What can I do to help my recovery?

The most important thing is to keep your fluid intake up, even if vomiting. Avoid fizzy or sugary drinks (including fruit juice) and milk. Oral rehydration solutions, available from pharmacies, are useful in severe dehydration because they also replace vital salts (water alone may be inadequate). For 48 hours, try to eat bland, non-greasy foods or soups and avoid grains, uncooked fruits and vegetables, and alcohol.

Antimotility medicines that slow the motility (movement) of your gut can help reduce any cramps and the frequency of toilet visits. They should be used as well as fluid replacement. This ‘slowing down’ of motility can sometimes help the body to absorb fluid. If the diarrhoea symptoms do not improve within 48 hours of using these medicines, see your doctor.

These medicines do not cure the cause of the diarrhoea. However, if tests reveal the problem is caused by a particular type of bacterium or parasite, your doctor may prescribe a course of antibiotics.

You should talk to your doctor if you also:

  • have blood or pus in your faeces
  • have a fever above 38ºC
  • 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 abdomen or rectum
  • 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.
    See further below for advice for infants and children.

How to avoid spreading gastroenteritis

‘Gastro’ spreads very easily to others. It is spread when a person touches something that has been in contact with diarrhoea, then puts their hand to their mouth. Some viruses can live on items (including children’s toys) for up to 14 days.
You can help prevent spreading the illness by:

  • washing your hands thoroughly with warm soapy water – especially after using the toilet, before preparing food and after nappy changes, if a child is unwell
  • washing and rinsing soiled clothing separately
  • not sharing food and drinks.

Dehydration in children over six months

Normally, with gastroenteritis causing diarrhoea and sometimes vomiting, you can expect your child to improve after a couple of days. But the younger the child, the easier it is for them to become dehydrated (very short of water).
The important signs of serious dehydration are:

  • dry mouth, lips and tongue, or no tears
  • sunken eyes or fontanelle (the soft spot on top of a baby’s head)
  • cold hands and feet, or mottled bluish skin
  • unusual lack of energy, sleepiness or difficult to wake
  • fewer wet nappies than usual, or unable to drink.

If your child has these signs call your doctor or call 111 for an ambulance.

How to treat dehydration by giving fluids

  • Increasing fluid intake is the main form of treatment.
  • Giving small amounts of fluid often is better than giving a large amount all at once. Aim for one teaspoon per minute (or approximately one-quarter of a cup every 15 minutes).
  • Keep offering your child fluids even if they are vomiting.
  • Your doctor may give you specific advice, and may want to review your child regularly. 

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).


  • 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. 


  • Do not give a child medicines to reduce the vomiting or diarrhoea. They may be harmful to children.
  • It is important to keep your child away from other children, daycare, Kohanga Reo and school until the diarrhoea has stopped. Some centres have specific policies – so check.

You should revisit your doctor if:

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

Drinks if child is not dehydrated

The following are suitable drinks for a child with gastroenteritis who is not dehydrated.
These must be diluted with water as they contain too much sugar.

Drink Water added
Cordial or Raro/refresh Make up to normal drinking strength then dilute one part with five parts of water
Soup Add five cups of water to one cup of soup
Fruit juice Add five cups of water to one cup of juice
Fizzy drinks Add five cups of warm water to one cup of drink (warm water removes the bubbles)

CAUTION: Undiluted soft drinks, fruit juice, sports drinks, Lucozade and Ribena should not be given to infants and children with diarrhoea - too much sugar increases the diarrhoea and dehydration.

Further information and support

  • 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.

Original material provided by everybody, July 2009. Reviewed by everybody, July 2013. Latest review by Health Navigator, November 2014.


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