What is bronchiolitis?

Bronchiolitis is a viral infection that causes the airways (bronchioles) in the lungs to become narrow, which makes breathing difficult. It occurs most often in children under age 2 during winter and early spring. Very rarely, adults can get bronchiolitis.

For instance, there is a condition called bronchiolitis obliterans, which is sometimes known as “popcorn lung.” This condition is usually caused by breathing in irritating chemicals or other substances.

What’s the difference between bronchiolitis and bronchitis?

These two conditions not only sound similar, but they are similar in some ways. Both can be caused by a virus. Both affect the airways in the lungs, but bronchitis affects the larger airways (the bronchi). Bronchiolitis affects the smaller airways (bronchioles). Bronchitis usually affects older children and adults, while bronchiolitis is more common in younger children.

What causes bronchiolitis?

The viruses that cause most cases of bronchiolitis are the respiratory syncytial virus (RSV), the rhinovirus and the influenza (flu) virus. These viruses are very contagious and are spread from person to person by touching secretions from the mouth or nose or by respiratory droplets in the air. The droplets get into the air when someone sneezes or coughs.

What are the signs and symptoms of bronchiolitis?

Signs and symptoms of bronchiolitis resemble those of colds and flu. They include:

  • Runny nose.
  • Slight fever (under 101 F).
  • Cough.
  • Rapid or shallow breathing.
  • Wheezing. This might be the first time that your child has wheezing. In bronchiolitis, this follows 3 days or so of the first three symptoms.

Your child might show more severe signs, including:

  • Making grunting noises.
  • Having trouble sucking and swallowing, which makes feeding difficult on top of having a poor appetite.
  • Trying so hard to breathe that their chest retracts (the skin is drawn down tightly against the rib cage and looks like it is going inward).
  • Turning blue or gray in the lips, fingertips or toes.
  • Being sluggish.

If you see that these things are happening, call your healthcare provider immediately or take your child to an emergency room. This is also true if your child is showing signs of dehydration, such as dry mouth, not urinating often and crying without producing tears. Dehydration is very serious in a young child.

How can you tell the difference between bronchiolitis and other diseases with the same symptoms?

Bronchiolitis does have symptoms that are similar to other lower respiratory infections like bronchitis and pneumonia. It also may seem like asthma, which is known to cause wheezing and trouble breathing. You might wonder if your child has aspirated (breathed in) something other than air. Any time that you notice that your child has problems breathing, you should call your healthcare provider. They are the ones who will be able to tell one kind of breathing issue from another.

Last reviewed by a Cleveland Clinic medical professional on 05/30/2020.


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  • American Academy of Pediatrics. Bronchiolitis. Accessed 6/1/2020.
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