Written by Brindles Lee Macon and Matthew Solan | Published on July 25, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP


Bronchiolitis is a viral respiratory condition that affects the smallest air passages in the lungs, the bronchioles. The job of these small, branching bronchioles is to control airflow in your lungs. When they become infected or damaged, they swell or become clogged. This blocks the flow of oxygen. Although it is generally a childhood condition, adults can be affected as well.  

Types of Bronchiolitis

There are two types of bronchiolitis.

Viral bronchiolitis is the most common and appears primarily in babies.

Bronchiolitis obliterans is a rare and dangerous condition seen in adults. In this condition, it is scarring, rather than swelling, that blocks the air passages and causes this condition.

What Causes Bronchiolitis?

Viral bronchiolitis is caused by viruses that enter and infect the respiratory tract. Viruses are microscopic organisms that can reproduce rapidly and challenge the immune system. The following are common types of viral infections that may bring on bronchiolitis.

Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus is the most common cause of bronchiolitis. RSV usually strikes babies less than 1 year of age. This contagious and dangerous viral infection produces inflammation, mucous, and swelling in the airways.


These viruses target mucous membranes and cause approximately 10 percent of all respiratory tract infections in children.

Influenza Viruses

These viruses produce inflammation in the lungs, nose, and throat. Influenza affects both adults and children, but is especially dangerous for babies whose immune systems are not strong.

Causes of Bronchiolitis Obliterans

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

  • fumes from chemical agents like ammonia, bleach, and chlorine
  • respiratory infections
  • adverse reactions to medications

Who is at Risk for Bronchiolitis?

Viral bronchiolitis affects children younger than 2 years, but generally manifests in infants 3 to 6 months of age. A few risk factors for viral bronchiolitis in babies and young children are:

  • not being breast-fed
  • being born prematurely or born with a heart or lung condition
  • having a depressed immune system
  • being exposed to cigarette smoke
  • being exposed to crowded environments, such as daycare centers, where the virus may be present

Common risk factors for bronchiolitis obliterans in adults are:

What are the Symptoms of Bronchiolitis?

Both viral bronchiolitis and bronchiolitis obliterans present similar symptoms. These include:

  • shortness of breath
  • bluish appearance to the skin from lack of oxygen
  • crackling or rattling sounds heard in the lungs
  • fatigue
  • ribs appear sunken as child attempts to inhale
  • nostrils flair in babies
  • fast breathing
  • racking or whooping type cough
  • wheezing or whistling sound when breathing

Symptoms for bronchiolitis obliterans can occur two weeks to a little over a month after exposure to chemicals. A lung infection can take several months to several years to produce symptoms.

How is Bronchiolitis Diagnosed?

There are several ways to diagnose both types of bronchiolitis. Imaging testing, including chest X-rays, is typically used to diagnose both adults and children. A common tool used in adults is spirometry, which measures how much, and how quickly, air is taken in with each breath. Blood gas tests for both bronchiolitis conditions measure how much oxygen and carbon dioxide are in the blood.

Samples of mucous or nasal discharge can be used to diagnose what type of virus is causing the infection. This testing method is commonly used with babies and small children.

How is Bronchiolitis Treated?

Viral bronchiolitis requires different treatments than bronchiolitis obliterans.

Treatments for Viral Bronchiolitis

Many cases of viral bronchiolitis are so mild that they clear up on their own without treatment. However, as this condition most often affects infants, hospitalization may be required for more severe cases. A hospital can provide any oxygen and intravenous fluid treatments that may be needed. Antibiotic medications are useless against viruses but some medications can be used to help open your baby’s airways.

Treatments for Bronchiolitis Obliterans

Although there is no cure for the scarring in bronchiolitis obliterans, corticosteroids can help rid the lungs of mucous, reduce inflammation, and open up the airways. Oxygen treatments and medications to boost the immune system may be necessary. Breathing exercises and stress reduction can help ease breathing difficulties. In the most severe cases of lung damage, a lung transplant may be the best recourse.

Home Care

Both conditions require extra rest and an increase in fluid intake. Keeping the air in the home clear of smoke and chemicals is very important. A moist-air humidifier may also help.

What is the Long-Term Outlook?

Children and babies with viral bronchiolitis usually improve in three days to a week with prompt, proper treatment. In obliterans, the prognosis varies depending on when the condition was found and how far it has progressed.

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