Merck Manual

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Quick Facts



The Manual's Editorial Staff

Last full review/revision Sep 2021| Content last modified Sep 2021
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What is bronchiolitis?

Bronchioles are small airways in your lungs. "-Itis" means inflammation. So bronchiolitis is inflammation of the small airways in the lungs. The inflammation makes it hard for children to breathe. Bronchiolitis happens in babies and children under age 2 years.

  • Bronchiolitis is caused by an infection from a virus

  • Your child may have a runny nose, fever, cough, wheezing, and sometimes trouble breathing

  • Most children get better at home in 3 to 5 days, but some need to be hospitalized

  • Bronchiolitis is most common in babies under 6 months

What causes bronchiolitis?

Doctors think bronchiolitis may be more common and more serious for babies whose mothers smoke cigarettes, especially if their mothers smoked during pregnancy.

What are the symptoms of bronchiolitis?

At first, your baby has symptoms of a cold, such as:

  • Runny nose

  • Sneezing

  • Coughing

  • Slight fever (100° to 101° F or 37.8° to 38.3° C)

The cough may last for 2 to 3 weeks or more.

After 3 to 5 days, your baby may have:

Many babies with bronchiolitis have only mild symptoms.

With severe bronchiolitis, your baby or child may have a lot of trouble breathing and symptoms like:

How can doctors tell if my child has bronchiolitis?

Doctors can usually tell if your child has bronchiolitis based on the symptoms. Doctors may also:

  • Measure the oxygen level in your child’s blood using a sensor on your child's finger (pulse oximetry)

  • Take a cotton swab of mucus from the nose to test for viruses

  • Sometimes, do a chest x-ray

How do doctors treat bronchiolitis?

Doctors will have you treat children with mild symptoms at home:

  • Give small amounts of clear fluids such as water or juice often during the day

If your child has a lot of trouble breathing, your child may have to be admitted to the hospital. Usually doctors will:

  • Give your child extra oxygen through a face mask

  • Give fluids through an IV (into the vein)

Antibiotics don't help bronchiolitis.

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