Mayo Clinic Health Library


Updated: 06-03-2011


Pneumonitis (noo-moe-NIE-tis) is a general term that refers to inflammation of lung tissue. Although pneumonia is technically a type of pneumonitis because the infection causes inflammation, most doctors are referring to other causes of lung inflammation when they use the term "pneumonitis."

Factors that can cause pneumonitis include exposure to airborne irritants at your job or while you participate in your hobbies. Some types of cancer treatments as well a dozens of drugs also can cause pneumonitis.

Difficulty breathing — often accompanied by a cough — is the most common symptom of pneumonitis. Specialized tests are necessary to make a diagnosis. Treatment focuses on avoiding irritants and reducing inflammation.



The most common sign of pneumonitis is shortness of breath, which may be accompanied by a dry cough. If pneumonitis is undetected or left untreated, you may gradually develop chronic pneumonitis. This is especially common in cases of hypersensitivity pneumonitis, in which you may be continually exposed to a lung irritant without realizing it. Signs and symptoms of chronic pneumonitis include:

  • Shortness of breath
  • Cough
  • Fatigue
  • Loss of appetite
  • Unintentional weight loss

When to call a doctor
Call your doctor anytime you have difficulty breathing.



Pneumonitis occurs when some irritating substance causes the tiny air sacs (alveoli) in your lungs to become inflamed. This inflammation can interfere with the delivery of oxygen to your bloodstream.

A variety of irritants, ranging from airborne molds to chemotherapy drugs, have been linked to pneumonitis. But for most people, the specific substance causing the inflammation is never identified. Pneumonitis causes may include:

  • Drugs. A variety of drugs used to treat other conditions can cause pneumonitis, including some antibiotics, several types of chemotherapy drugs and medications that keep your heartbeat regular. An overdose of aspirin can cause pneumonitis.
  • Molds. Specific varieties of mold-related pneumonitis have received nicknames, such as "farmer's lung" or "hot tub lung."
  • Birds. Exposure to feathers or bird excrement is a common cause of pneumonitis.
  • Radiation treatments. Some people who undergo radiation therapy to the chest, such as for breast or lung cancer, may develop pneumonitis. Pneumonitis also can occur after whole-body radiation therapy, which is needed to prepare a person for a bone marrow transplant.

Risk factors

Occupations or hobbies
Some occupations and hobbies carry higher risks of pneumonitis, including:

  • Farming. Many types of farming operations expose workers to aerosolized mists and pesticides. Inhaling airborne particles from moldy hay is one of the most common causes of occupational pneumonitis. Mold particles also can be inhaled during harvests of grain and hay.
  • Bird handling. Poultry workers and people who breed or keep pet birds are often exposed to droppings, feathers and other materials that can cause pneumonitis.
  • Hot tubs and humidifiers. Moldy conditions in hot tubs can trigger pneumonitis, because the bubbling action makes a mist that can be inhaled. Home humidifiers are another common reservoir for mold.

Cancer treatment
Some chemotherapy drugs can cause pneumonitis, as can radiation therapy to the lungs. The combination of the two increases the risk.



Pneumonitis that goes unnoticed or untreated can cause irreversible lung damage. Normally, air sacs within your lungs stretch and relax with each breath. Chronic inflammation of the thin tissue lining each air sac can make the air sacs scar and become inflexible — stiff like a dried sponge. This is called pulmonary fibrosis. In severe cases, pulmonary fibrosis can cause heart failure, respiratory failure and death.


Preparing for your appointment

While you may initially consult your family physician, he or she may refer you to a pulmonologist — a doctor who specializes in lung disorders.

What you can do
You may want to write a list that includes:

  • Detailed descriptions of your symptoms, including when they began and if anything seems to make them worse or better
  • Information about medical problems you've had and their treatments
  • Information about the medical problems of your parents or siblings
  • All the medications and dietary supplements you take
  • Questions you want to ask the doctor

What to expect from your doctor
A thorough medical history and physical exam can provide important clues about what might be causing your symptoms. Your doctor may ask some of the following questions:

  • Do you now or have you ever smoked tobacco?
  • What types of occupations have you had?
  • Do you have a hot tub or humidifier at home?
  • Are you ever around pigeons or pet birds?

Tests and diagnosis

To distinguish pneumonitis from other lung disorders, you'll likely have one or more of the following tests.

Imaging tests
In most cases, pneumonia affects only a small, localized portion of your lungs, while the effects of noninfectious pneumonitis are often spread throughout all five lobes of your lungs.

  • Chest X-ray. This painless test causes a small amount of radiation to pass through your chest to produce images of your lungs. X-rays take only a few minutes to perform.
  • Computerized tomography (CT). CT scans combine X-ray images taken from many different angles into detailed cross-sectional images. This painless test involves lying on a narrow table that slides into a large, doughnut-shaped machine. CT scans typically take less than 15 minutes to perform. Computerized tomography gives much greater detail of changes in your lungs than what a chest X-ray can provide.

Pulmonary function tests
A test called spirometry measures the amount of air that you're able to inhale and exhale in a specific period of time. Your doctor may also measure how efficiently your lungs transfer gases from the air into the bloodstream during exercise.

Another way to assess the efficiency of your lungs is to measure the oxygen saturation in your blood with an oximeter — a device that painlessly clamps on your finger.

A bronchoscopy is a procedure that uses a flexible tube threaded down your throat to view your airways and collect samples from your lungs. Once the tube is in place, your doctor may flush a section of your lung with a saltwater solution to collect lung cells and other materials. This flushing procedure is known as a lavage. Your doctor may also insert a tiny tool through the bronchoscope to remove a small sample of cells from the lung tissue for testing.

Surgical lung biopsy
In some cases, your doctor may want to examine a larger sample of tissue from several locations within your lungs that cannot be reached via bronchoscopy. A surgical procedure to obtain these samples may be necessary.


Treatments and drugs

If you have hypersensitivity or chemical pneumonitis, avoiding allergens is a common-sense approach to treatment. By eliminating exposure to the allergen or chemical irritating your lungs, you'll likely notice that your symptoms lessen.

In severe cases of pneumonitis, treatment may include:

  • Corticosteroids. Drugs that reduce inflammation, such as prednisone, can help relieve the symptoms of pneumonitis. Corticosteroids are usually taken as a pill. These drugs work by suppressing your immune system, reducing inflammation in your lungs. However, long-term corticosteroid use also increases your risk of developing infections and is associated with the thinning of bones (osteoporosis).
  • Antibiotics. If you have a bacterial infection in your lungs, your doctor may prescribe an antibiotic, which may be given through a vein in your arm or taken as a pill, depending on the severity of the infection.
  • Oxygen therapy. If you're having a lot of trouble breathing, you may need oxygen therapy through a mask or plastic tubing with prongs that fit into your nostrils. Some people need oxygen therapy constantly, while others might need it only during exercise or sleep.

Lifestyle and home remedies

A diagnosis of pneumonitis may mean that you'll have to make changes to your lifestyle in order to improve your health.

For example, if your job duties expose you to substances that irritate your lungs, talk to your doctor and supervisor at work about options to protect yourself, such as wearing a pollen mask or personal dust respirator. If a hobby, such as owning birds, is causing the problem, you'll have to consider giving it up altogether.