Hypersensitivity Pneumonitis Symptoms and Diagnosis

What Are the Symptoms of Hypersensitivity Pneumonitis?

Hypersensitivity pneumonitis is typically divided into two types based on how long you have been affected and how severe your symptoms are.

An attack of acute hypersensitivity pneumonitis usually occurs four to six hours after a short period of intense exposure to the substance you are allergic to. You may feel as if you have caught the flu when an acute attack occurs. Common symptoms include fever, chills, muscle aches, headache and cough. These symptoms may last for as little as 12 hours to a few days and will resolve if further exposure is avoided.

Chronic hypersensitivity pneumonitis develops after numerous or continuous exposures to small amounts of the allergen. Symptoms may include shortness of breath, tiredness, coughing that lasts weeks or months and weight loss that gets progressively worse. Over time, some people with chronic hypersensitivity pneumonitis develop clubbing of fingers and toes and irreversible pulmonary fibrosis.

How Hypersensitivity Pneumonitis Is Diagnosed

If you suspect your symptoms are hypersensitivity pneumonitis, schedule an appointment with your doctor. Because of the risk of progressive chronic disease, it is important to get a prompt diagnosis. Your doctor will ask about your exposures, perform a physical examination and listen to your lungs with a stethoscope. Individuals with hypersensitivity pneumonitis may have abnormal lung sounds or crackles. Your doctor may also use a small instrument called a pulse oximeter that is placed on the finger to check the oxygen levels in your blood.

Some specific questions that your doctor may ask are:
  • Have you been exposed to any water damage in your house or at work, especially from humidifiers, heating systems or air conditioners?
  • What types of substances are you regularly exposed to in your work?
  • Do you have a hot tub at home?
  • Have you have been exposed to bird droppings/do you have any birds as pets/do you have any feather cushions or down pillows?

If your physician is unsure of your diagnosis, they may order additional tests. These include:

  • Chest X-ray and CT scan which may be able to show early stages of the disease and if there is any scarring.
  • Lung function tests to measure how well you breathe to see if your lungs are working correctly.
  • Blood tests to find out if you have developed antibodies to any substances that might be causing an allergic reaction.
  • Bronchoscopy, which is when a bronchoscope (small flexible tube about the size of a pencil with a video camera attached at its end) is passed either through your nose or mouth. The scope is then passed into your vocal cords, windpipe and the air passages. This tool can be used to collect tissue samples from your lung for further testing.

Surgical lung biopsy, which is performed by a cardiothoracic surgeon under general anesthesia. It is another way to get lung tissue for further testing.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: November 17, 2022

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