Merck Manual

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Rajeev Bhatia

, MD, Phoenix Children's Hospital

Reviewed/Revised Jan 2022 | Modified Sep 2022
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Croup is an inflammation of the windpipe (trachea) and voice box (larynx) typically caused by a contagious viral infection that causes cough, a loud squeaking noise (stridor), and sometimes difficulty with breathing in (inspiration).

  • Croup is caused by viruses.

  • Symptoms include fever, runny nose, and a typical bark-like cough.

  • The diagnosis is based on symptoms.

  • Most children recover at home, but those who require hospitalization receive fluids, oxygen, and drugs.

Croup primarily affects children 6 months to 3 years of age.

Most children have only a single episode of croup, but a few have repeated episodes (called spasmodic croup), initiated by viral infections, that gradually decrease in frequency and severity. Allergies or airway reactivity (such as occurs in asthma Asthma in Children Asthma is a recurring inflammatory lung disorder in which certain stimuli (triggers) inflame the airways and cause them to temporarily narrow, resulting in difficulty breathing. Asthma triggers... read more Asthma in Children ) may play a role in spasmodic croup.

Causes of Croup

Croup is caused by a viral infection that leads to swelling of the lining of the airways, particularly the area just below the voice box (larynx).

The most common cause of croup is

  • Parainfluenza viruses

Although croup occurs throughout the year, seasonal outbreaks are common. Croup caused by parainfluenza viruses tends to occur in the fall, and croup caused by RSV and influenza viruses tends to occur in the winter and spring. The infection usually is spread by breathing in airborne droplets containing viruses or by having contact with objects contaminated by these droplets.

Symptoms of Croup

Croup usually starts with symptoms of a cold—runny nose, sneezing, mild fever Fever in Infants and Children Normal body temperature varies from person to person and throughout the day (it is typically highest in the afternoon). Normal body temperature is higher in preschool-aged children and highest... read more Fever in Infants and Children , and some coughing Cough in Children Cough helps clear materials from the airways and prevent them from going to the lungs. The materials may be particles that have been inhaled or substances from the lungs and/or airways. Most... read more . Then the child develops hoarseness and a frequent, unusual-sounding cough, which is described as brassy or barking. Croup ranges widely in its severity. Sometimes swelling of the airway causes difficulty breathing, which is most noticeable when breathing in (inspiration). In severe croup, there may be a loud squeaking noise (stridor Stridor Stridor is a gasping sound during inhalation resulting from a partial blockage of the throat (pharynx), voice box (larynx), or windpipe (trachea). Stridor is usually loud enough to be heard... read more ) heard with each inspiration. About 50% of children have a fever. All symptoms are typically much worse at night and may awaken children from sleep. Symptoms often seem to lessen in the morning and worsen again the next night.

The worst of the symptoms usually lasts 3 to 4 days, and the cough continues but changes to a looser-sounding cough. This change can cause concern for parents who think the infection has moved to the chest. However, it is the normal progression of the illness.

Diagnosis of Croup

  • Sound of the cough

  • Neck x-rays

A doctor distinguishes croup by its characteristic symptoms, especially the sound of the cough.

Prognosis for Croup

Most children with croup recover completely.

Treatment of Croup

  • For mild illness, fluids and humidified air

  • For severe illness, hospitalization, oxygen, epinephrine, and corticosteroids

If a child develops a croupy breathing pattern, the parents should contact the doctor because children with croup can become very ill very quickly.

Mildly ill children may be cared for at home and usually recover in 3 to 4 days. The child should be made comfortable, given plenty of fluids, and allowed to rest because fatigue and crying can worsen the condition. Home humidifying devices (for example, cool-mist vaporizers or humidifiers) may reduce drying of the upper airways and ease breathing. The humidity can be raised quickly by running a hot shower to steam up the bathroom. Carrying the child outside to breathe cold night air or to the kitchen to breathe cold air from the freezer also may open the airways. Although these remedies are harmless, there is little scientific evidence that they make any difference in how children feel.

Did You Know...

  • Breathing humidified air in a steamy bathroom or cool air from the freezer may help lessen croup symptoms.

For sicker children, the doctor may recommend a single dose of a corticosteroid to prevent worsening of symptoms. Children with worsening symptoms should be seen immediately by a doctor who will likely recommend corticosteroids and may hospitalize the child for observation and care.

Children who have increasing or continuing difficulty in breathing, rapid heart rate, fatigue, dehydration, or bluish skin discoloration need to be given oxygen, as well as fluids by vein. Doctors usually treat children with epinephrine given in a nebulizer and corticosteroids given by mouth or injection. These drugs help shrink swollen tissue in the airways. Children who improve with these treatments may be sent home, but children who are very ill should remain in the hospital.

Antibiotics are used only in the rare situation when a child with croup also develops a bacterial infection. Rarely, a ventilator Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more (a breathing machine that helps air get in and out of the lungs) is needed.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
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