Croup factsheet


Croup is a childhood illness that is caused by common viruses.

Croup happens when a virus causes the airways to swell and produce too much mucus. 

The airways affected by croup include the:

  • larynx – the voice box
  • trachea – the windpipe.

Swelling and mucus make it harder for your child to breathe in and out. This causes the trachea to collapse in on itself. Children with croup will have a rough, bark-like cough.

Croup is most common during winter. It usually affects children between six months and three years old. This is because their airways are smaller and softer.

 Signs and symptoms

Symptoms of croup include:

  • a raspy voice
  • wheezing
  • stridor - a harsh, high-pitched noise when your child breathes in and out
  • a bark-like cough
  • chest retractions - where the chest pulls in as your child coughs and breathes
  • difficulty breathing, especially when upset.

Croup is caused by viruses like the common cold, so your child may also have symptoms like:

  • a sore throat
  • fever
  • red eyes
  • runny nose.

Croup can last from a few days to a week. Symptoms will generally be worse during the first few days and at night.

The croup cough can sometimes last longer but will not usually cause any permanent damage.


Your child’s doctor can diagnose croup based on their signs and symptoms.


Breathing difficulties can be a medical emergency in children. See your local doctor as soon as possible, or present to your nearest emergency department.

Most children do not need to be admitted to the hospital and can go home from the emergency department once they have been treated.

Your child’s doctor may give some medications to reduce the swelling and help your child breathe more easily. These medications are usually given using a nebuliser. A nebuliser is a device that turns medications into a mist that your child can breathe in.

Antibiotics do not treat croup because it is caused by a virus.


Looking after your child at home

There is no evidence that steam can treat croup and cold symptoms. Steam can cause burns if it is not used properly. 

Your child might become stressed and upset when they have difficulty breathing, which can make their breathing issues worse. 

Try to calm and comfort your child, encouraging them to rest and drink plenty of fluids.

Spasmodic croup

Some children have croup episodes that happen suddenly at night and settle after an hour. This is known as spasmodic croup.

Spasmodic croup is more common in children with asthma or a family history of asthma and allergies.

When to seek help

If your child has any of the following symptoms, take them to a local doctor or your closest emergency department straight away.

  • breathing is becoming more difficult
  • cyanosis after coughing - a blue, green, or grey colour in the skin around places like the mouth, nail beds and gums
  • being restless, irritable, or delirious 
  • chest retractions – when the skin around the ribs pulls in as your child breathes 
  • high fever that does not respond to treatment 
  • dribbling or drooling more than usual
  • dehydration, or not having enough fluid
  • stridor noise when breathing, even when your child is resting
  • you are concerned for any other reason.
Last updated Tuesday 7th May 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024