Gastroenteritis (gastro)

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    Gastroenteritis (gastro) is a bowel infection that causes diarrhoea (runny, watery poo) and sometimes vomiting. The vomiting may settle quickly, but the diarrhoea can last up to 10 days.

    Gastro can be caused by many different germs, although the most common cause of gastro is a viral infection. Most children do not need to take any medicine for gastro; however, it is important that they drink plenty of water to avoid becoming dehydrated.

    Gastro is spread easily, and is more common and severe in babies and young children. Babies under six months old can become dehydrated very easily and need to be checked by a GP if they have gastro.

    Signs and symptoms of gastro

    If your child has gastro, they may:

    • feel unwell, and not want to eat or drink
    • vomit in the first 24 to 48 hours (usually before diarrhoea begins)
    • have diarrhoea, which can last up to 10 days
    • have some stomach pain
    • have a fever.

    Care at home

    The main treatment is to keep your child drinking fluids often such as water, oral rehydration solution, breastmilk or formula. It is very important to replace the fluids lost due to the vomiting and diarrhoea.

    Gastrolyte, HYDRAlyte, Pedialyte and Repalyte are different types of oral rehydration fluid that can be used to replace fluids and body salts. These are the best option if your child is dehydrated. They are also available as icy poles, which children are often happy to have.

    If your child refuses water or oral rehydration fluids, try diluted apple juice. Do not give drinks that are high in sugar (e.g. flat lemonade or sports drinks), because they can make dehydration worse. You can give your child their usual milk; however, some children may not feel like drinking milk if they have gastro.


    If your baby is under six months old, they should always be seen by a doctor if they have gastro. For babies over six months:

    • If you are breastfeeding your baby, continue to do this but feed more often. Offer your baby a drink every time they vomit. You can also give an oral rehydration solution or water for the first 12 hours.
    • If you are bottle feeding your baby, replace formula feeds with oral rehydration solution or water for the first 12 hours, then give normal formula in small, but more frequent amounts. Offer your baby a drink every time they vomit. 

    Older children 

    • Give small amounts of fluid often – give a few mouthfuls every 15 minutes for all children with diarrhoea or vomiting. This is especially important if your child is vomiting a lot.
    • Your child may refuse food when they first get gastro. This is not a problem as long as they are drinking fluids.

    Do not give your child over-the-counter medicines that reduce vomiting and diarrhoea, as the medicines may be harmful for children.

    Children with gastro are infectious, so wash your hands thoroughly after contact with your child, particularly before feeding and after nappy changes. Keep your child away from other children as much as possible until the diarrhoea has stopped.

    When to see a doctor

    Babies under six months old should always be checked by a GP if they have gastro, because they are at higher risk of dehydration.

    Any child with gastro should see a GP if they:

    • are vomiting and have diarrhoea, and are not drinking
    • have a lot of diarrhoea (eight to 10 watery poos, or two or three large poos per day) or if the diarrhoea is not improving after 10 days
    • vomit frequently and seem unable to keep any fluids down
    • show signs of dehydration e.g. fewer wet nappies or not going to the toilet much, dark yellow or brown wee, feel lightheaded or dizzy, have dry lips and mouth
    • have a bad stomach pain
    • have any blood in their poo
    • have green vomit
    • are making you worried for any other reason.

    If your child is very dehydrated and cannot keep any fluids down, they may need to be admitted to hospital to have fluids by a tube through the nose into the stomach (a nasogastric tube) or directly into a vein through a drip (intravenous or IV therapy).

    Key points to remember

    • Babies under six months old with gastro can become dehydrated very easily and need to be checked by a GP.
    • Offer babies a drink every time they vomit. Keep breastfeeding. If bottle feeding, give oral rehydration solution for the first 12 hours.
    • Give children small amounts of fluid often.
    • Your baby or child is infectious, so regularly wash your hands thoroughly, particularly before feeding and after nappy changes.
    • Take your child to the doctor if they are becoming dehydrated, have bad stomach pain or you are worried.

    For more information

    Common questions our doctors are asked

    I’m concerned the fluids I am giving my child is making the diarrhoea worse. Should I give her less to drink?

    It is very important for fluids to be given, even if the diarrhoea seems to get worse. It is important to replace the fluids that are lost due to diarrhoea or vomiting to prevent dehydration.

    Should I be worried that my child doesn’t want to eat when he has gastro?

    When your child first gets gasto they may refuse food to start with. This is not a problem as long as they are drinking fluids. When your child becomes hungry again, give them the food they feel like eating.

    Can my child have dairy after a bout of gastro?

    Many children become sensitive to dairy following a bout of gastro. You can usually manage this by reducing their dairy intake for a period of three weeks following gastro. If the symptoms persist beyond this, take your child back to your GP.

    Developed by The Royal Children's Hospital General Medicine, Emergency and Gastroenterology departments, and Centre for Community Child Health. We acknowledge the input of RCH consumers and carers.

    Reviewed February 2018.

    This information is awaiting routine review. Please always seek the most recent advice from a registered and practising clinician.

    Kids Health Info is supported by The Royal Children’s Hospital Foundation. To donate, visit


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