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Alternative Names
acute laryngotracheobronchitis

Croup is an infection of the tissues around the vocal cords in young children. It has a characteristic cough and can cause difficulty breathing.

What is going on in the body?
The symptoms of croup are caused by the swelling and inflammation of the tissues around the larynx and vocal cords. The diameter of the upper airway in young children is narrow to begin with, so this swelling further reduces the size of the airway. This makes breathing more noisy and laboured.

Croup generally affects young children between 3 months and 5 years of age. Boys are affected more often than girls. About 15% of children with croup have a family history of croup. Some children have repeated episodes of croup.

When a virus that can cause croup moves through a community, only some children will develop croup. Most children will have symptoms of a cold or laryngitis, such as congestion, cough, hoarseness, or sore throat.

What are the signs and symptoms of the infection?
Croup has a characteristic cough that sounds like a barking seal. This cough is what sets croup apart from other upper respiratory infections. Croup often begins abruptly, most often in the middle of the night. Typically, a young child will have some cold symptoms but will seem okay when put to bed. The parents are awakened in the middle of the night by the barking sound of the croupy cough. This often occurs in spasms and may even cause the child to vomit. The child often feels that he or she cannot breathe. This may cause the child and the parents to panic. This only makes breathing more difficult and causes additional distress.

Often the croupy cough is accompanied by a noise called "stridor." This noise is made when the child is breathing in, or inhaling. Stridor is actually a more worrisome symptom than the cough because it means that the airway has narrowed significantly. This is especially true if the child has stridor when he or she is at rest and is not upset or crying.

A child with croup may or may not have a fever.

What are the causes and risks of the infection?
Croup is caused by a viral infection. The parainfluenza virus is a family of viruses that accounts for 75% of cases of croup.

The major risk of croup is that the child's upper airway may swell so much that the child may not be able to breathe. This is called severe upper airway obstruction. As the diameter of the airway becomes more narrowed, the resistance to the flow of air increases. The child must exert more and more energy to supply enough air to his or her lungs. If the work of breathing is not somehow relieved, the child may become exhausted, go into a coma, and die. However, the majority of cases of croup do not reach this level.

What can be done to prevent the infection?
Croup is difficult to prevent. The viruses that cause it are common, especially in the winter months. Most young children are not immune to these viruses, and effective vaccines to them are not currently available. One exception is the vaccine for the influenza virus, which accounts for only a small percentage of croup cases.

Some things can be done:
  • Breast-feeding provides some protection to infants against these common infections. This is probably through the transmission of maternal antibodies in the breast milk.
  • Avoiding tobacco smoke may lessen the risk of infants and young children getting respiratory infections.
  • Children in day care or preschool have greater exposure to these viruses.
  • There is no solid evidence that multiple or large doses of vitamins prevent respiratory viral infections.
How is the infection diagnosed?
Croup is a clinical diagnosis. This means that it is diagnosed by observing a characteristic set of symptoms and physical signs.

There are several other conditions that must be investigated because their treatment is much different than croup. One is a foreign body lodged in the upper airway. In this case, the child may have stridor and respiratory distress, but have no recent cold symptoms.

Epiglottitis is a serious and rapidly progressive, bacterial infection of the epiglottis, a flap of tissue at the base of the tongue that seals off the airway during swallowing so that food or liquids do not go down the airway. Children with epiglottitis appear in great distress, have severe pain in their throats, and are unable to swallow even their own saliva. They do not have a "barking seal" cough.

What are the long-term effects of the infection?
Croup usually is a short-term illness without long-term effects. For some children it can be a recurrent illness. Sometimes, a child with severe croup requires inserting a breathing tube, called an airway intubation, or an emergency cutting of a hole in the trachea below the larynx, or voice box, to insert a tube for breathing, called a tracheostomy. This may lead to scarring of the trachea or vocal cords, which in turn, could affect the quality of the voice or narrow the airway.

What are the treatments for the infection?
Since croup is usually caused by a viral infection, antibiotics are not helpful in treating the infection. Relieving the swelling and respiratory distress are most helpful.
  • For milder cases, a cool mist vaporiser should be placed near the child's bed. This may help reduce the cough and airway irritation.
  • For the child who awakens at night coughing and in distress, the best thing to do is to "steam up" the bathroom. This can be done by running hot water in the shower. Parents should then have the child sit in the bathroom breathing in the steam. Parents should stay with the child until he or she settles down.
  • Once a child has settled down, he or she should be put back to bed with a vaporiser near the bed.
The child should have some relief from the above measures in about 10 to 15 minutes. If he or she is experiencing an alarming degree of respiratory distress, the ambulance should be called at 000 or the child should be taken to the hospital emergency department.

Emergency department treatment usually consists of giving the child oxygen, a special form of adrenaline that is inhaled, and a dose of steroids, either oral, inhaled or injectable. If the child does not respond to these measures, he or she will be admitted to the hospital.

After admission children will have their blood oxygen saturation level monitored. This is the amount of oxygen that is carried in the child's bloodstream. The child may be given frequent doses of the inhaled form of adrenaline and will be watched very closely for any changes in breathing. Other management may include a single dose of corticosteroids. In rare cases, a child may need a breathing tube inserted. This provides an adequate airway for several days until the airway swelling goes down.

What are the side effects of the treatments?
adrenaline can cause a temporary rapid heartbeat. A single dose of corticosteriods does not have any significant side effects. A child who requires intubation could have some vocal cord damage or airway scarring. This may be temporary or permanent.

What happens after treatment for the infection?
There is no special treatment needed after the child recovers from an episode of croup.

How is the infection monitored?
Younger children with a tendency to develop croup should be watched closely for early signs of croup whenever they develop signs and symptoms of an upper respiratory infection.

Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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