Pneumonitis (noo-moe-NIE-tis) is a general term that refers to inflammation of lung tissue. Technically, pneumonia is a type of pneumonitis because the infection causes inflammation. Pneumonitis, however, is usually used by doctors to refer to noninfectious causes of lung inflammation.

Common causes of pneumonitis include airborne irritants at your job or from your hobbies. In addition, some types of cancer treatments and dozens of drugs can cause pneumonitis.

Difficulty breathing — often accompanied by a dry (nonproductive) 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 symptom 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, which can result in scarring (fibrosis) in the lungs.

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, no matter what might be the cause.

Pneumonitis occurs when an irritating substance causes the tiny air sacs (alveoli) in your lungs to become inflamed. This inflammation makes it difficult for oxygen to pass through the alveoli into the bloodstream.

Many 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 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 and bacteria. Repeated exposure to some molds and bacteria can cause the lungs to become inflamed. 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.

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 pigeons 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 of irreversible lung disease.

Pneumonitis that goes unnoticed or untreated can cause irreversible lung damage.

In normal lungs, the air sacs stretch and relax with each breath. Chronic inflammation of the thin tissue lining each air sac causes scarring and makes the sacs less flexible. They become stiff like a dried sponge. This is called pulmonary fibrosis. In severe cases, pulmonary fibrosis can cause right heart failure, respiratory failure and death.

During the physical exam, your doctor will use a stethoscope to listen carefully to your lungs while you breathe. To distinguish pneumonitis from other lung disorders, you'll likely have one or more of the following tests.

Blood tests

Certain blood tests can be useful for pinpointing a diagnosis.

Imaging tests

Imaging tests are useful because 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 how well your lungs are working is to measure the oxygen in your blood with an oximeter — a device that painlessly clamps on your finger.

Bronchoscopy

A bronchoscopy is a procedure that uses a flexible tube threaded down your throat to view your airways and collect samples from your lungs.

During bronchoscopy, 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 scope 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 larger samples of tissue from several locations in your lungs that cannot be reached via bronchoscopy. A surgical procedure to obtain these samples may be necessary.

If you have hypersensitivity or chemical pneumonitis, your doctor will recommend eliminating exposure to the allergen or chemical irritating your lungs. This step should help lessen your symptoms.

In severe cases of pneumonitis, treatment may also include:

• Corticosteroids. These drugs work by suppressing your immune system, reducing inflammation in your lungs. Corticosteroids are usually taken as a pill. However, long-term corticosteroid use also increases your risk of developing infections and is associated with the thinning of bones (osteoporosis).
• 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.

A diagnosis of pneumonitis may mean that you'll have to make changes to your lifestyle to protect your health. You'll need to avoid known triggers as much as possible.

For example, if your job duties expose you to substances that irritate your lungs, talk to your doctor and supervisor at work about ways to protect yourself, such as wearing a pollen mask or personal dust respirator. If a hobby is causing the problem, you may have to find a different hobby.

While you may initially consult your family doctor, 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
• Detailed list of all jobs and exposures that may have accompanied these occupational activities
• 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 or have taken in the last few years?
• 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 jobs or hobbies have you had?
• How does the severity of your breathing symptoms relate to your work or hobby schedules?
• Do you have a hot tub or humidifier at home?
• Are you ever around pigeons or pet birds?