Bronchiolitis is swelling and mucus buildup in the smallest air passages in the lungs (bronchioles), usually due to a viral infection.


Bronchiolitis usually affects children under the age of 2, with a peak age of 3 - 6 months. It is a common, and sometimes severe illness. Respiratory syncytial virus (RSV) is the most common cause. More than half of all infants are exposed to this virus by their first birthday.

Other viruses that can cause bronchiolitis include:

You can catch the virus if you come into direct contact with nasal fluids or airborne droplets from someone who has the illness. This may happen if the person sneezes or coughs near you.

Bronchiolitis is seasonal and appears more often in the fall and winter months. It is a very common reason for infants to be hospitalized during winter and early spring.

Risk factors for bronchiolitis include:

  • Being around cigarette smoke
  • Age younger than 6 months old
  • Living in crowded conditions
  • Not being breastfed
  • Prematurity (being born before 37 weeks gestation)


Some children may have few or minor symptoms.

Bronchiolitis begins as a mild upper respiratory infection. Over a period of 2 - 3 days, the child develops more breathing problems, including wheezing and a "tight" wheezy cough.

Symptoms include:

  • Bluish skin due to lack of oxygen (cyanosis) - emergency treatment is needed
  • Breathing difficulty including wheezing and shortness of breath
  • Cough
  • Fatigue
  • Fever
  • Muscles around the ribs sink in as the child tries to breathe in (called intercostal retractions)
  • Nasal flaring in infants
  • Rapid breathing (tachypnea)

Exams and Tests

The health care provider will perform a physical exam and listen to the lungs. This may reveal:

  • Wheezing and crackling sounds heard through stethoscope exam of chest

Tests that may be done include:

  • Blood gases
  • Chest x-ray
  • Culture of a sample of nasal fluid to determine the virus causing the disease


Sometimes, no treatment is necessary. Antibiotics do not work against viral infections. Most medications do not help treat bronchiolitis.

Supportive therapy can include:

  • Drinking plenty of fluids. Breast milk or formula are okay for children younger than 12 months. Electrolyte-balanced drinks, such as Pedialyte, are also okay to use in infants.
  • Breathing moist (wet) air to help loosen sticky mucus. You can use a humidifier to moisten the air your child is breathing. Follow the directions that come with the humidifier.
  • Getting plenty of rest.
  • Not letting anyone smoke in the house, car, or anywhere near your child.

Children in the hospital may need oxygen therapy and fluids given through a vein (IV).

Rarely, antiviral medications, such as ribavirin, may be used to treat extremely ill children.

Outlook (Prognosis)

Usually, the symptoms get better within a week. Breathing difficulty usually gets better by the third day.

Possible Complications

  • Airway disease, including asthma, later in life
  • Respiratory failure
  • Additional infection, such as pneumonia

When to Contact a Medical Professional

Call your health care provider immediately, or go to the emergency room if the child with bronchiolitis:

  • Becomes extremely tired
  • Has bluish color in the skin, nails, or lips
  • Starts breathing very fast
  • Has a cold that suddenly worsens
  • Has difficulty breathing
  • Flares nostrils or retracts chest muscles in an effort to breathe


Most cases of bronchiolitis are not easily preventable because the viruses that cause the disorder are common in the environment. Careful attention to hand washing, especially around infants, can help prevent the spread of respiratory viruses.

Family members with an upper respiratory infection should be especially careful around infants. Wash your hands often, especially before handling the child.

At this date, there is no RSV vaccine available. However, there is an effective product, called palivizumab (Synagis), for infants who are at high risk of developing severe disease from RSV. Ask your child's doctor whether this medication is right for your child.


Watts KD, Goodman DM. Wheezing, bronchiolitis, and bronchitis. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 383.

American Academy of Pediatrics Subcommittee on the Diagnosis and Management of Bronchiolitis. Diagnosis and management of bronchiolitis. Pediatrics. 2006;118:1774-1793.

Updated: 4/2/2012

Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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