Croup is an inflammation of the larynx and trachea, mostly seen in young children. A barking cough, varying degrees of airway obstruction, and hoarseness are the defining symptoms.

A range of infectious conditions can lead to croup. It is also known as laryngotracheobronchitis.

The barking cough that is characteristic of croup results from swelling and inflammation around the vocal chords and windpipe. Symptoms normally improve within a few days, but hospitalization may be needed in severe cases.

Croup affects 3 percent of children between 6 months and 3 years of age in the United States.

Fast facts on croup

  • Croup is an infection of the larynx and trachea, occurring mostly in children.
  • It is characterized by a barking cough and can be caused by either viruses and bacteria.
  • There 17 stages for grading the severity of croup.
  • Symptoms will normally self-resolve. One dose of a corticosteroid drug called dexamethasone can help prevent the return of symptoms.
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Croup is categorized either by the cause or the specific symptoms that accompany the cough.

Viral croup

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Croup is recognizable by its distinctive barking cough.

Viral croup is the most common type.

Acute croup is most often caused by a virus, as is recurrent, or spasmodic, croup. They have a similar presentation, making it difficult to distinguish between the two for diagnosis.

Some researchers argue that spasmodic croup may be linked to allergens such as pollen or a bee sting, or that it may be an allergic reaction to viral antigens, rather than a direct result of a viral infection.

Bacterial croup

Bacterial croup is caused by a bacterial infection. This type is much rarer than viral croup and can be divided into bacterial tracheitis, laryngotracheobronchitis (LTB), laryngotracheobronchopneumonitis (LTBP), and laryngeal diphtheria.

The main symptom of croup is a “barking cough” that may begin suddenly during the night.

A child may also experience a runny nose, sore throat, congestion, and mild fever a few days before the start of cough symptoms. Croup is usually mild and lasts less than a week. Severe cases occur due to breathing difficulties caused by swelling of the upper part of the windpipe.

Symptoms are mild in 85 percent of children examined at the emergency room for signs of croup. Severe croup is rare and accounts for less than 1 percent of cases.

Other symptoms may include:

  • noisy breathing, or a rasping sound when breathing in, known as stridor
  • hoarse throat
  • other problems with breathing
  • the chest moving up and down more than normal during breathing
  • rash
  • eye redness
  • swollen lymph nodes
  • dehydration
  • low oxygen levels
  • blue-tinged skin on the fingers, toenails, earlobes, the tip of the nose, lips, tongue, and the inside of the cheek
  • rarely, a high fever will occur

Uncommon complications of croup include pneumonia, pulmonary edema, and bacterial tracheitis.

Croup can have several causes.

Viral croup

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Respiratory syncytial virus is one of the causes of viral croup.

Types 1, 2, and 3 of the human parainfluenza virus account for 80 percent of all cases of croup.

Human parainfluenza virus 1 (HPIV-1) is the most common cause of croup, with types 1 and 2 causing 66 percent of infections. Type 4 has been associated with milder illness but is not well understood.

The following viruses cause the remaining cases of croup:

Viral infection typically takes the following course to develop into croup:

  1. The virus infects the nose and throat.
  2. The virus spreads along the back of the throat to the larynx and trachea.
  3. As the infection progresses, the top part of the trachea becomes swollen.
  4. The space available for air to enter the lungs becomes narrower.
  5. Children compensate for this by breathing more quickly and deeply, leading to croup symptoms.
  6. The child may become restless or anxious as breathing becomes more difficult. This agitation can also narrow the throat, increase breathing difficulties and worsening the agitation.
  7. The effort required to breathe faster and harder is tiring, and, in severe cases, the child may become exhausted and unable to breathe on their own.

Croup also has genetic indications. Both spasmodic croup and acute croup are more common in children with a family history of croup. The risk of spasmodic croup may also be increased by a previous attack.

Bacterial croup

Bacterial infection usually affects the same areas as a viral infection but is typically more severe and requires different treatment.

Most instances of bacterial croup, more commonly called bacterial tracheitis, are due to secondary bacterial infection from Staphylococcus aureus (S. aureus). Other bacteria that cause croup include S. pyogenes, S. pneumonia,Haemophilus influenza, and Moraxella catarrhalis.

Diagnosis can confirm the type and severity of the condition.

It is most likely to occur in infants, toddlers, and young children between the ages of 3 months and 6 years.

As breathing passages are larger in older children and adolescents, upper respiratory tract swelling and inflammation usually do not result in croup symptoms. Although rare, children over 6 years can get croup.

A variety of scoring systems have been developed to evaluate the severity of croup. Below is a table demonstrating each level of severity using the Westly and Alberta Clinical Practice Guideline Working Group guidelines.

Level of severityCharacteristics
Mild Level 0 to 2
  • occasional barking cough
  • intermittent or absent airway obstruction
  • no chest wall retraction or cyanosis
  • normal physical appearance
Level 3 to 5
  • barking cough
  • persistent audible stridor at rest
  • some chest wall retraction
  • agitation that can be calmed
  • child still responds to caregivers and the surroundings
Severe Level 6 to 11
  • frequent barking cough
  • prominent airway obstruction at rest
  • marked chest wall retraction
  • significant agitation, distress, and lethargy
  • a fast heartbeat with severe obstructive symptoms
Impending respiratory failure Level 12 to 17
  • barking cough, but often not prominent
  • audible obstruction during rest that may occasionally be hard to hear
  • retractions of the chest wall
  • lethargy or decreased level of consciousness
  • darkened skin in the absence of oxygen.

Is it contagious?

Croup is caused by viruses that can spread through the mucus and droplets from coughing or sneezing. Children with croup should be considered contagious for 3 days after the illness begins or until any fever is gone.

An infection by a virus that causes croup in a young child may cause a cough or a sore throat in an older child or adult. It is unlikely to cause the breathing difficulties of croup. However, in rare cases, symptoms of croup can occur in teenagers or adults.

In cases severe enough to warrant medical attention, a doctor will recommend treatment options and will decide if admission to hospital is necessary.

Croup is often mild and can be managed at home. A single dose of oral dexamethasone may be prescribed. The doctor will advise a parent or caregiver on how to manage symptoms and when to seek further medical attention.


Dexamethasone is a corticosteroid drug.

Randomized controlled trials (RCTs) have found that a single dose of oral dexamethasone in children with mild croup reduces the number of children returning for medical attention in the following 7 to 10 days.

If a child is very young, has certain underlying medical conditions, or seems very ill, the doctor may recommend an evaluation before prescribing any medication.

Steroid medicines do not shorten the length of the illness but have anti-inflammatory effects and are likely to reduce the severity of breathing problems.

Home management

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Keeping a child calm is important for avoiding flare-ups of croup symptoms. Crying can make symptoms worse.

There is a range of strategies to help parents and caregivers manage symptoms of croup at home.

Remaining calm and reassuring is important for any caregiver looking after a child with croup. This is because small children with croup can easily become distressed, and crying can make symptoms worse.

Children with noisy breathing should be placed in an upright position.

When to seek medical help

Any caregiver who notices any of the following signs of symptoms should seek further medical help:

  • breathing becomes difficult for the child
  • the child is very pale or blue
  • the child becomes agitated, delirious, or restless
  • their breastbone is drawn back on breathing
  • the child has a high temperature and is drooling
  • the child is severely agitated alongside respiratory distress

Croup typically resolves within 48 hours. It may be followed by symptoms of upper respiratory tract infection (URTI).

Take a child to the doctor if any of the following symptoms are noticeable:

  • Breathing symptoms get worse, including breathing rapidly, needing more effort to breathe, and pulling in the chest or neck muscles with each breath.
  • The child becomes restless or agitated.
  • The child looks unusually pale.
  • A high fever persists despite giving acetaminophen or ibuprofen.

An emergency ambulance should be called if the child is:

  • blue
  • lethargic
  • struggling to breathe
  • drooling and unable to swallow

More information on managing croup

The following have been found to be effective in relieving the symptoms of moderate-to-severe croup in the hospital:

  • Oxygen: This should be reserved for children with low oxygen and significant respiratory distress.
  • Nebulized adrenaline, or epinephrine: This is required for severe croup only. It offers improvements up to 30 minutes after administration for acute croup. Nebulized adrenaline has been consistently demonstrated by studies to benefit children with moderate-to-severe croup
  • Glucocorticoids: Dexamethasone, budesonide, and prednisone have been shown to be effective up to 12 hours after treatment.
  • Intubation: This is a procedure involving the insertion of a tube into the airway. Intubation is only required in about 1 percent of croup cases when the airway obstruction is not relieved by conservative treatment, and the condition of the child continues to deteriorate.

Acetaminophen and ibuprofen can also be used to control fever and pain. Applying a damp sponge is not recommended for controlling fever.

It is also important to ensure adequate fluid intake. Humidifiers or cool mist vaporizers are often used to relieve croup, but they may not be as effective as previously thought.

Cough medicines and decongestants are not effective for relieving symptoms of croup.

Parents and caregivers should also note that, if symptoms occur suddenly at night, croup usually resolves by itself. Exposing the child to cool night air may relieve mild respiratory distress.

Antibiotics are not usually prescribed for viral croup as they are not effective unless there is a secondary bacterial infection.

Croup can seem distressing for a child, but it is often mild and short-lived.

Keeping your child comfortable and hydrated will often allow the illness to run its course without any other treatment except, in some cases, a single dose of dexamethasone.

Croup can lead to severe breathing problems, but this is uncommon.