12 min read

What is croup?

Croup is a childhood condition that affects the windpipe (trachea), the airways to the lungs (the bronchi) and the voice box (larynx).

A child with croup has a distinctive barking cough and will make a harsh sound, known as stridor, when they breathe in.

A blocked airway can also cause a hoarse voice and breathing difficulties.

Croup can usually be diagnosed by a doctor and treated at home. However, if your child’s symptoms are severe and they are finding it difficult to breathe, take them to the nearest hospital’s accident and emergency (A&E) department.

Read more about the

symptoms of croup
diagnosing croup

Why does croup happen?

Commonly, croup is caused by a viral infection. In 80% of cases, the parainfluenza virus is responsible.

In some cases, croup may be caused by an allergic reaction.

There are two types of croup:

  • viral croup (laryngotracheitis), which develops over several days and is caused by an infection
  • spasmodic croup, which involves repeated, short-lasting episodes of croup that can be caused by an allergic reaction

The same treatments are recommended for both viral croup and spasmodic croup.

Read more about the

causes of croup

Who is affected?

Croup usually affects young children aged between six months and three years, with most cases occurring in two-year-olds. However, croup can sometimes develop in older children up to 15 years of age.

About three in 100 children will suffer from croup every year. The condition is more common during the late autumn and early winter months.

It tends to affect more boys than girls.

It is occasionally possible for a child to experience croup more than once during childhood.

Treating croup

Most cases of croup are mild and get better on their own, without the need for treatment. Sitting your child upright and comforting them if they are distressed is important, because crying may make symptoms worse. Your child should also drink plenty of fluids to prevent dehydration.

More severe cases of croup may need to be treated with steroids to reduce the swelling in the throat.

If your child has breathing problems, hospital treatment, such as adrenaline and an oxygen mask may be required.

Read more about

treating croup


Around 60% of croup cases clear up within 48 hours. However, in some cases symptoms can last for up to two weeks.

It is very rare for a child to die from croup.

There are a number of conditions that can follow croup, such as

middle ear infection

Read more about the

complications of croup

Preventing croup

Croup is spread in a similar way to the common cold, so it is difficult to prevent.

Good hygiene is the main defence against croup, such as regularly washing hands and cleaning surfaces.

A number of your child's routine vaccinations also protect against some of the infections that can cause croup. These include:

  • MMR - protection from measles, mumps and rubella
  • DTaP/IPV/Hib - protection from diphtheria, tetanus, whooping cough, polio and Haemophilus influenzae type b

Signs of croup

A child can get croup at any time of the year, although it's more likely to occur during late autumn or early winter.

This may be because there are more

and viruses around at this time of year.

Initial symptoms of viral croup are similar to those of a cold. They can include a:

Over 1-2 days, specific symptoms that are characteristic of croup will develop. These include:

  • a bark-like cough
  • a hoarse or croaky voice
  • difficulty breathing
  • a harsh grating sound when breathing in called stridor
  • difficulty swallowing

Symptoms of spasmodic croup are similar to those mentioned above. However, a bark-like cough and stridor tend to occur suddenly, usually at night.

Stridor is often most noticeable when the child cries or coughs. However, in more severe cases of croup it can also occur when the child is resting or sleeping.

Symptoms tend to be worse at night. Although they usually only last for a few days, they can occasionally last up to two weeks.

When to seek medical advice

Croup can usually be diagnosed by a doctor and mild cases can be treated at home.

However, seek immediate medical attention if your child has any of the following symptoms:

  • severe breathing difficulties
  • an increased breathing rate (they're too breathless to feed or talk) or 'silent chest' (you're unable to hear sounds of breathing)
  • a worsening cough or rasping sound (stridor)
  • distress and agitation
  • dark, blue-tinged or pale skin
  • the skin around their ribs and chest appears to be pulled in and tight, making the bones of their chest and ribs more visible
  • abnormal drowsiness and sleepiness
  • a rapid heartbeat or a falling heart rate

You should take them to your nearest hospital's accident and emergency (A&E) department or call for an ambulance.

Some of these symptoms may indicate a potentially life-threatening underlying condition called

(inflammation and swelling of the epiglottis).

The symptoms could also indicate tracheitis (inflammation of the windpipe), which also requires immediate medical attention.

Croup causes

Croup usually develops as the result of a viral infection. The infection causes the larynx (voice box) to become swollen and the trachea (windpipe) to become blocked.

Parainfluenza virus

The parainfluenza virus is the most common cause of croup. Four strains of the virus are responsible for around 80% of croup cases. These are:

  • parainfluenza I
  • parainfluenza II
  • parainfluenza III
  • parainfluenza IV

Parainfluenza I is responsible for most cases of croup.

The virus can be transmitted through close contact with infected people, as well as contaminated objects and surfaces. As with many airborne viruses, the parainfluenza virus is often spread by breathing in droplets from infected coughs or sneezes.

Other viruses

A number of other viruses can also cause croup. These include:

  • influenza A and B (flu viruses)
  • the
    virus, in children who have not been immunised against measles
  • the
    herpes simplex virus
    (cold sore virus)
  • the
    varicella-zoster virus
    (chickenpox virus)
  • the adenovirus
  • the rhinovirus
  • enteroviruses
  • the metapneumovirus
  • the respiratory syncytial virus (RSV), which can cause severe breathing problems and
    in babies

Other causes

Less common causes of croup include:

  • an allergic reaction to substances such as pollen or dust mites
  • inhalation of irritants, such as chemicals
  • acid leaking back out of the stomach and into the throat (
    acid reflux

How is croup diagnosed?

A doctor can diagnose croup by studying your child's symptoms, particularly the sound of their cough. They may also check your child's temperature for a fever and ask whether they have recently had a cold or viral infection.

In some cases, a pulse oximetry test may be carried out. This involves clipping a sensor onto your child's earlobe or finger, in order to determine their level of oxygen intake. The test determines whether your child is absorbing enough oxygen into their blood.

A throat swab may also be taken, in order to identify the virus or bacteria responsible for the condition.

Your doctor will decide whether hospital admission is required or whether your child's croup is safe to treat at home.

You should not try to check your child's throat yourself, because it could trigger a spasm (sudden narrowing) of the airway. This could cause the airway to swell even more, making breathing even more difficult.

Ruling out other conditions

Although croup can usually be diagnosed by studying your child’s symptoms. Your doctor may want to rule out other conditions that can cause similar symptoms.

Other possible causes for your child’s symptoms are:

  • an abnormality of the airway, which has been present from birth
  • an
    in the tissues in the back of the throat
  • inhaled material
  • swelling of the deeper layers of the skin (angio-oedema)

In very rare cases,

(inflammation of the epiglottis) or tracheitis (inflammation of the windpipe) can cause similar symptoms to croup. In these cases, however, your child will usually feel very unwell generally, rather than just having the specific symptoms of croup.

Differentiating these causes from croup may require further tests.

Further investigation

If your child is admitted to hospital with severe croup, or if treatment proves unsuccessful, further investigations may be needed to examine their neck and chest area for a possible obstruction.

An X-ray may be recommended if it is thought something may have been inhaled and is obstructing your child’s airway.

Treatment for croup

Treatment of croup depends on how severe the symptoms are. Most cases do not need treating as the condition usually gets better on its own after a short period of time.

However, if your child has severe croup, they will need to be admitted to hospital urgently.

Comforting your child

Comforting your child is important because their symptoms may worsen if they are agitated or crying.

If your child is distressed, sitting them upright on your lap will help to comfort and reassure them.

Treating mild croup

Mild cases of croup can be managed at home. If your child has a fever,

children's paracetamol
will help lower their temperature.

Your child should also drink plenty of fluids to ensure they remain well hydrated.

While there is little scientific evidence to support it, some people have found that allowing their child to breathe in steam from a hot bath or shower in a closed room has eased symptoms.

Steam treatment should only be used under careful supervision as there is a risk of scalding your child.

You should seek urgent medical advice if you notice your child’s symptoms getting worse.


Painkillers, such as paracetamol and

, are available in liquid form, which makes them ideal for young children. You can get liquid paracetamol over the counter from pharmacies and some supermarkets.

Children under 16 years of age should not be given aspirin.

Speak to your pharmacist or doctor if you are unsure about what type of painkiller is suitable for your child.

Cough medicines or decongestants do not help ease the symptoms of croup and should not be used. These treatments often have drowsy side effects, which can be dangerous when a child has breathing difficulties.

More severe croup

If your child has more severe croup, your doctor may decide to prescribe

to help ease their symptoms. Corticosteroids reduce inflammation (swelling) in the throat.

Dexamethasone or prednisolone are often used to treat croup.

This type of medication can be taken as a tablet or inhaled using a nebuliser (an inhaler device).

Potential side effects of these corticosteroids include:

  • restlessness
  • vomiting
  • upset stomach
  • headache

Hospital treatment

Breathing problems, such as shortness of breath, are a major symptom of severe croup.

You should dial 999 immediately for an ambulance if your child is struggling to breathe.

If your child has severe croup, they will be given adrenaline through a nebuliser. This will help improve symptoms within 10 to 30 minutes and the effects should last for up to two hours.

If your child is very distressed and are finding it difficult to breathe, they will be given oxygen through an oxygen mask.

An oral corticosteroid will also be given to help reduce any inflammation (swelling) in your child’s airways. Dexamethasone or prednisolone is usually prescribed for cases of severe croup.

However, if your child is unable to tolerate the side effects of this treatment, they may be given another type of corticosteroid called budesonide. If necessary, a nebuliser can be used to administer the medication.

In less than 1% of croup cases that require hospitalisation, a child may need intubation. During intubation a tube is inserted either through a nostril or the mouth and passed down into the windpipe. This will help your child breathe more easily.

Intubation is usually performed under

general anaesthetic
. This means your child will be completely unconscious throughout the procedure so they do not experience pain or distress.

Complications of croup

Complications that develop as a result of croup are rare, with less than 5% of children needing a hospital visit.

Airway obstruction

If an obstructed airway is not treated promptly, it can lead to:

  • severe breathing difficulty (respiratory distress)
  • respiratory arrest (where breathing stops but the heart continues beating)

Always call for an ambulance if your child is struggling to breathe.

Your child may find it difficult to drink fluids as a result of an obstruction in their airway. However, it is important they have plenty of fluids to avoid


If your child refuses fluids, try not to force them. This could distress your child and make the condition worse.

Secondary infection

A secondary infection can sometimes develop following the initial viral infection that caused croup. A secondary infection can potentially cause:

  • pneumonia
    , which is swelling of the tissue in one or both lungs, usually caused by an infection
  • bacterial tracheitis, which is a serious and potentially life-threatening infection that can occur after a viral respiratory infection

Other complications

Although rare, other possible complications of croup can include

middle ear infection
and lymphadenitis, an infection of the glands of the immune system (lymph nodes).

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.