Bronchiolitis is an inflammatory respiratory condition. It’s caused by a virus that affects the smallest air passages in the lungs (bronchioles). The job of the bronchioles is to control airflow in your lungs. When they become infected or damaged, they can swell or become clogged. This blocks the flow of oxygen. Although it’s generally a childhood condition, bronchiolitis can also affect adults.


There are two main types of 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 1 year old.

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.

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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. This contagious and dangerous viral infection produces 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 they’re left untreated. A few causes have been identified and include:

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

Viral bronchiolitis affects children up to 2 years old. But it generally occurs in infants 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 depressed immune system
  • being exposed to cigarette smoke
  • being in crowded places where the virus is present, like day care centers

Common risk factors for bronchiolitis obliterans in adults are:

  • working conditions that expose you to dangerous chemicals
  • having had a heart, lung, or bone marrow transplant
  • smoking tobacco containing nicotine
  • having an autoimmune connective tissue disease

Both 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

After exposure to certain chemicals, bronchiolitis obliterans symptoms can appear within two weeks to a month. A lung infection can take several months to several years to produce symptoms.

There are several ways to diagnose both types of bronchiolitis. Imaging testing, including chest X-rays, helps doctors diagnose 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 for both bronchiolitis types measure how much oxygen and carbon dioxide are in your blood.

Samples of mucus or nasal discharge can help your doctor diagnose the type of virus causing the infection. This testing method is common with babies and small children.

Viral bronchiolitis requires different treatments than bronchiolitis obliterans.

Treatments for viral bronchiolitis

Many cases of viral bronchiolitis are mild and clear up without treatment. For more severe cases in infants, hospitalization may be necessary. A hospital can provide oxygen, a nebulizer, and intravenous fluid treatments. Antibiotic medications don’t work against viruses, but some medications can help open your baby’s airways.

Treatments for bronchiolitis obliterans

There’s no cure for the scarring of bronchiolitis obliterans. Corticosteroids can help clear the lungs of mucus, reduce inflammation, and open up the airways. You may need oxygen treatments and immunosuppressant medications to regulate your immune system. Breathing exercises and stress reduction can help ease breathing difficulties. Sometimes a lung transplant may be the best option in the most severe cases.

Recovery from both conditions requires extra rest and increased fluid intake. Keeping the air in your home clear of smoke and chemicals is very important. A humidifier to keep the air moist may also help.

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