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.


Viral Bronchiolitis

Viral bronchiolitis appears in infants. Most cases of viral bronchiolitis are due to respiratory syncytial virus (RSV). Viral outbreaks occur every winter and affect children under the age of one.

Bronchiolitis Obliterans

Bronchiolitis obliterans is a rare and dangerous condition seen in adults. This disease causes scarring in the bronchioles. This blocks the air passages creating an airway obstruction that can’t be reversed.


Viral bronchiolitis and bronchiolitis obliterans have similar signs and symptoms. These include:

  • Shortness of breath
  • Wheezing
  • Bluish appearance of the skin from lack of oxygen
  • Crackling or rattling sounds heard in the lungs
  • Fatigue
  • Ribs that appear sunken during attempts to inhale (in children)
  • Nasal flaring (in babies)
  • Fast breathing
  • Cough

Exposure to certain chemicals may cause bronchiolitis to appear within two weeks to a month. A lung infection can take several months to several years to produce symptoms.


There are different causes of viral bronchiolitis and bronchiolitis obliterans.

Causes of Viral Bronchiolitis

Viruses that enter and infect the respiratory tract cause viral bronchiolitis. Viruses are microscopic organisms that can reproduce rapidly and challenge the immune system. The following are common types of viral infections that may cause bronchiolitis:

Respiratory Syncytial Virus (RSV)

RSV is the most common cause of bronchiolitis. RSV usually strikes children by the age of 2 but is most common in babies less than 1 year of age. Contagious infection can also cause inflammation, mucus, and swelling in the airways.


These viruses target mucous membranes. They cause about 10 percent of acute respiratory tract infections in children.

Influenza Viruses

These viruses cause inflammation in the lungs, nose, and throat. Influenza affects both adults and children. It’s especially dangerous for babies who don’t have strong immune systems.

Causes of Bronchiolitis Obliterans

This rare condition sometimes occurs for no known reason. Severe cases can lead to death if left untreated. A few cases have been identified and include:

  • Fumes from chemicals like ammonia, bleach, and chlorine
  • Respiratory infections
  • Adverse reactions to medications


Viral bronchiolitis can affect children up to 2 years old. It generally occurs in infants of 3 to 9 months of age. A few risk factors for viral bronchiolitis in babies and young children are:

  • Not being breastfed
  • Being born prematurely or born with a heart or lung condition
  • Having a suppressed immune system
  • Being exposed to cigarette smoke

Risks for Bronchiolitis Obliterans in Adults

  • Working conditions can expose you to dangerous chemicals
  • Having a heart, lung, or bone marrow transplant
  • Smoking tobacco containing nicotine
  • Having an autoimmune connective tissue disease


There are several ways to diagnose bronchiolitis. Imaging tests, including chest X-rays that help doctors to diagnose this bronchiolitis. A common tool used for adults is spirometry. This measures how much and how quickly you take in air with each breath. Arterial blood gas tests are used to test both types of bronchiolitis and measure how much oxygen and carbon dioxide are present in the blood. Samples of mucus or nasal discharge can help the doctor to diagnose the type of virus causing the infection. This testing method is common with babies and small children.


There are no specific vaccines or treatments for bronchiolitis. Antibiotics and cold medicines are not effective in treating bronchiolitis. Most cases go away on their own and can be treated at home. It is essential that your child drink plenty of fluids to avoid dehydration. To help your baby breathe, your doctor may recommend saline nasal drops. It's also an easy approach to clear your child's nasal passages using a suction bulb. If you have a fever, your doctor may prescribe acetaminophen. About 3% of youngsters with bronchiolitis will require hospitalization. Here the child can receive humidified oxygen and receive intravenous fluids to prevent dehydration. For more severe cases, a tube may need to be inserted into the windpipe to help the child breathe. Most children will be sent home in 2 to 8 days in the hospital.

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Frequently Asked Questions

1. What Causes Bronchiolitis?

A viral infection is nearly often the cause of bronchiolitis. In most cases, the culprit is a respiratory syncytial virus (RSV). RSV is a very common virus, and almost all children are infected by the age of 2.

2. Is bronchiolitis the same as pneumonia?

Both are lung conditions with similar symptoms, so it can be difficult to tell the difference. However, each of them affects different parts of the lungs: Bronchitis affects the bronchial tubes that carry air to the lungs. Pneumonia affects the air sacs, called alveoli, where oxygen passes into the blood.

3. Is bronchiolitis the same as asthma?

In many clinical studies, all wheezing illnesses other than asthma in children younger than 3 years have been diagnosed as bronchiolitis. Asthma is a chronic inflammation of the airways and, clinically, an acute asthma attack simulates bronchiolitis.