Bronchiolitis Symptoms, Causes, and Risk Factors | American Lung Association

Bronchiolitis Symptoms, Causes, and Risk Factors

What Are the Symptoms of Bronchiolitis?

Not everyone with bronchiolitis will have symptoms. When symptoms do occur, they are usually related to inflammation in the small airways. Shortness of breath and coughing are most common. When caused by an irritating substance, people may experience irritation in other parts of the body, including the eyes, nose and throat. Bronchiolitis should be considered when these symptoms do not improve with treatment for common lung diseases, such as asthma or viral infection.

What Causes Bronchiolitis?

Bronchiolitis is the result of injury to the small airways in the lung. Different types of injury may cause different appearance of the small airways under the microscope after lung biopsy and a good way to think of bronchiolitis is that it is a general term to describe a pattern of lung damage that can occur for many different reasons. For example, bronchiolitis that occurs after inhaling a toxic substance is caused by direct damage to the small airways. Bronchiolitis that occurs with some forms of arthritis is caused by the immune system effect on the small airways.

What Are Risk Factors?

A person is at higher risk for developing bronchiolitis whenever they are exposed to a respiratory infection, inhaled irritant and medical condition where injury to the small airways may occur. Common categories of risk factors for bronchiolitis include:

  • Infections - including common cold viruses, influenza, measles and some forms of pneumonia.  Young children are most at risk for developing bronchiolitis caused by infections.
  • Inhaling toxic substances - including acid, chlorine, ammonia or smoke.
  • Medications - including gold, penicillamine, sulfasalazine and rituximab.
  • Arthritis - including rheumatoid arthritis and lupus.
  • Organ transplantation

When to See Your Doctor

You should consult with your healthcare provider if you experience coughing and breathlessness that does not go away or that occurs after a respiratory infection or inhaling a toxic substance.


    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


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