Pneumonitis is inflammation of lung tissue, often within the alveoli or tiny air sacs. People with pneumonitis may experience shortness of breath alongside a dry cough and fatigue. The condition often begins with the inhalation of an irritant that triggers the inflammation. Pneumonia is a specific type of pneumonitis. Pneumonitis has many possible causes, and it is often impossible to determine the triggering irritant.

Molds and Bacteria

Experts have proven that regular exposure to certain molds and bacteria may cause pneumonitis. This also includes the spores of some mushroom species. Doctors will often refer to specific varieties of these forms as “farmer’s lung” or “hot tub lung.” In some cases, it is not the irritants themselves that are responsible for the inflammation but a person’s specific hypersensitivity to the materials.

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Viral Infections

Certain viral infections can potentially have pneumonitis as a symptom. Viruses that may be responsible include adenoviruses, herpes simplex virus, influenza A and B viruses, and cytomegalovirus. Of these, the measles virus is perhaps the most notable example. Because pneumonia is a form of pneumonitis, some of the viruses responsible for pneumonia may also cause pneumonitis.

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Medications and Drugs

Some medications and drugs can cause pneumonitis. This includes antibiotics, a few chemotherapy medications, and some heart disease treatments. Some people develop pneumonitis after an overdose of aspirin. Additionally, allergic or adverse reactions to any medication could include pneumonitis along with their many complications.

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Radiation Treatment

People who undergo radiation therapy that targets the chest may develop pneumonitis. This type of radiation therapy is most common in treating breast or lung cancer. Individuals in need of a bone marrow transplant will receive whole-body radiation therapy to prepare them for the procedure. In rare cases, this may also result in pneumonitis.

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Risk Factors

Certain people have a higher risk of developing pneumonitis. Various farming operations expose workers to aerosols, mists, and pesticides. Additionally, working with moldy hay or grain leads to inhaling potentially dangerous particles. Individuals who handle birds like poultry or pigeons are also at risk because of the potential exposure to droppings, feathers, and other materials. Moldy hot tubs and humidifiers can also create a dangerous, inhalable mist.

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Doctors can use a variety of methods to diagnose pneumonitis. They may begin by listening to the lungs. Blood tests or imaging tests like X-rays or a CT scan can also provide important diagnostic information. Spirometry, a common pulmonary function test, may be necessary to determine how efficiently the lungs are working.

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Some experts separate pneumonitis into distinct classifications, depending on the triggering irritant. These include:

  • Hypersensitivity pneumonitis from organic dust like bacteria or mold
  • Acute interstitial pneumonitis from many different irritants
  • Chemical pneumonitis from toxic substances reaching the lower airways
  • Radiation pneumonitis from radiation treatment
  • Aspiration pneumonitis from inhaling harmful gastric contents

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Doctors recommend that people with hypersensitivity or chemical pneumonitis eliminate exposure to the irritant that is causing their condition. To treat pneumonitis, a physician may prescribe corticosteroids to suppress the immune system and reduce inflammation. They may also prescribe bronchodilators to open up the airways for better airflow. Oxygen therapy can help those with difficulty breathing. Some people require constant oxygen therapy, though others only need it while sleeping.

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If doctors do not discover the pneumonitis soon enough, it may develop into a serious complication. Recurrent pneumonia is common, as is pulmonary fibrosis. Some people experience flares causing respiratory distress that could be life-threatening. Rarely, the condition may result in a collapse of one of the lungs, known medically as pneumothorax.

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Assuming a doctor can identify and treat the condition before it worsens, people with pneumonitis have a good prognosis. A late diagnosis can lead to progressive, irreversible lung disease. Some lifestyle changes may be necessary if a hobby, career, or environment is responsible for the irritant that triggered the pneumonitis.

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