What Is It?

Croup is a common respiratory illness in children that causes a hoarse voice and a brassy, barking cough. Doctors sometimes call croup laryngotracheitis because it usually involves inflammation of the larynx (voice box) and trachea (windpipe).

Croup often is divided into two broad categories: infectious croup and spasmodic croup.

Infectious Croup
Infectious croup is caused by an infection with a virus, bacterium or other germ. In the United States, most cases of croup are caused by the parainfluenza virus, which usually causes respiratory infections in the fall and winter when people spend more time indoors. Under these conditions, parainfluenza spreads easily through the tiny droplets expelled by coughs and sneezes. It also can travel on dirty hands and on items that have been soiled by fluids from a sick person’s nose or mouth. These include dirty tissues, shared toys and contaminated drinking glasses and eating utensils.

Once the parainfluenza virus enters the body, it usually begins to attack the upper parts of the respiratory tract. For this reason, a child with croup may first complain of cold symptoms, such as a runny nose or nasal congestion. The child also may have a low-grade fever or a mild sore throat. Later, as the virus spreads farther down the throat, the linings of the voice box and windpipe become red, swollen, narrowed and irritated. This triggers hoarseness, a barking cough, and loud, raspy breathing (stridor).

Spasmodic Croup
Spasmodic croup is thought to be caused by an allergic reaction to viruses, the same viruses that cause infectious croup. However, in spasmodic croup, the linings of the voice box and trachea are swollen but do not show signs of infection. In some cases, the airway irritation seems to be triggered by stomach acid that has come back up into the throat.

Spasmodic croup tends to start suddenly, without any cold symptoms. It usually does not cause a fever.

In the United States, infectious and spasmodic croup account for about 15 percent of all respiratory illnesses seen by pediatricians. Infectious croup is most common in children younger than age 6, and boys are affected slightly more often than girls. Spasmodic croup usually affects children who are between 3 months and 3 years old. Before the age of 3 months, a child’s risk of either type of croup is fairly low. This is probably because protective antibodies pass from the mother to the child before birth or in breast milk.


The classic symptom of croup is a harsh, brassy cough that sounds like a seal’s bark. This cough is often worse at night, and it usually occurs with hoarseness and loud, raspy breathing. Other symptoms vary, depending on whether the illness is infectious croup or spasmodic croup.

Infectious Croup
Children with infectious croup often have a low-grade fever and mild cold symptoms before a cough begins. In many cases, the sick child also has a history of being exposed to a family member, friend or classmate with a cough, runny nose or other signs of a respiratory infection.

Most children with infectious croup are mildly ill and never develop significant breathing problems. Among the few who do develop more severe forms of the illness, symptoms can include:

  • Rapid or labored breathing
  • Flaring nostrils
  • An abnormal sucking in of the chest and abdominal muscles (retractions) as the child struggles to take a breath
  • Unusual restlessness or agitation
  • A blue tint to the skin, especially at the lips and fingernails

Spasmodic Croup
A child with spasmodic croup often looks fairly healthy before coughing starts. Episodes of cough and loud, raspy breathing generally start without warning, typically in the middle of the night. These symptoms often will pass if the child is carried into cool night air or taken into a steamy bathroom. Symptoms from spasmodic croup usually improve within a few hours, although it is common for the symptoms to reappear several nights in a row.


After reviewing your child’s symptoms, the doctor will ask whether your child has been exposed to anyone with a cough or cold. The doctor also will review your child’s immunizations, especially immunizations for Haemophilus influenzae. These bacteria can cause epiglottitis, a potentially life-threatening infection that can block the windpipe suddenly. Symptoms of epiglottitis can be similar to those of croup.

Usually, your child’s doctor can diagnose croup based on your child’s history, symptoms and a physical examination. If your child’s symptoms are severe or unusual, X-rays or other tests may be needed to check for more severe illnesses of the lungs or throat, including epiglottitis. Rarely, when a child has severe breathing difficulties, hospital care is necessary.

Expected Duration

Symptoms of infectious croup usually go away within three to five days. However, some children have a mild cough that lasts a bit longer.

In children with spasmodic croup, several episodes of croupy cough may occur during one night. This pattern may repeat for four or five nights in a row.


To help prevent viral infections that can cause croup:

  • Wash your hands frequently, especially after you blow your nose. Also, wash your hands after you care for someone who has a cough, cold or sore throat.
  • If someone in your household has a respiratory infection, keep his or her eating utensils and drinking glasses separate from those of other family members. Wash these glasses and utensils thoroughly in hot, soapy water.
  • If a toddler with a respiratory infection has been chewing or sucking on toys, wash these toys with soap and water and then rinse them well.
  • Promptly dispose of dirty tissues from runny noses and sneezes.
  • Ask anyone with a cough or cold to avoid kissing or playing with your child.

Researchers are developing several potential vaccines against parainfluenza virus. In the future, one of these vaccines may be used to immunize children against croup.


If your child has croup, your doctor probably will recommend measures to make breathing easier until the infection goes away. These measures include:

  • Rest or quiet play
  • Ibuprofen (Advil, Motrin and other brand names) or acetaminophen (Tylenol) to relieve any discomfort
  • Drinking plenty of fluids, which will prevent dehydration and help to move mucus out of the airways
  • A cool mist vaporizer, because cool mist soothes and moistens the inflamed airways and helps mucus drain

In some cases, your doctor also may prescribe corticosteroid drugs, such as dexamethasone (Decadron) or prednisone (sold as a generic) to relieve airway inflammation.

Most children with croup have mild forms of the illness that can be treated at home. In particular, spasmodic croup often improves dramatically with only a cool mist vaporizer.

In rare cases, a child with croup can develop severe breathing problems that must be treated in a hospital. In this setting, the child can receive oxygen, epinephrine (a drug that opens the airways), corticosteroids and other measures to aid breathing.

When To Call A Professional

If your child appears to have severe breathing problems, either call for emergency help immediately, or take your child to an emergency room. Some danger signs to watch for include:

  • Labored breathing with flaring nostrils or retractions
  • Blueness of the lips or fingernails
  • Restlessness or confusion
  • Sleepiness or lethargy
  • Severe bouts of coughing that last for more than one minute and interfere with breathing
  • Excessive drooling
  • High fevers


The majority of children with croup recover fully without complications.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.