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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:

• Occupational exposure to airborne particles, such as asbestos or silica
• Some drugs, particularly chemotherapy drugs
• Radiation therapy to the chest
• Exposure to poultry, pigeons or pet birds
• Many types of mold

Difficulty breathing — often accompanied by a cough — is the most common symptom of pneumonitis. But having these problems doesn't necessarily mean that you have pneumonitis. Specialized tests are necessary to make a diagnosis.

The most common signs and symptoms of pneumonitis are:

• Difficulty breathing
• Cough
• A fever, which can be low-grade

Chronic pneumonitis
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 an allergen 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
Give your doctor a call anytime you have difficulty breathing, with or without a cough — especially if your symptoms appear after you inhale dust or chemicals, or if you are taking a medication that might cause shortness of breath.

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

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.

Drugs
A variety of drugs used to treat other conditions can cause pneumonitis.

• Antibiotics. Nitrofurantoin, amphotericin B, minocycline, sulfasalazine and sulfadiazine have been linked to pneumonitis.
• Chemotherapy drugs. The types of cancer-fighting drugs most likely to cause pneumonitis include bleomycin, methotrexate, carmustine, busulfan and cyclophosphamide.
• Heart drugs. Medicines to keep your heartbeat regular, such as amiodarone, may cause pneumonitis in some people.

Fungi and other allergens
Specific varieties of pneumonitis have received nicknames such as "farmer's lung" or "hot tub lung." The lung irritants involved include:

• Mold
• Feathers or bird excrement

Radiation treatments
Some people who undergo radiation therapy to the chest for cancer may develop pneumonitis. This is most likely to occur in people being treated for:

• Lung cancer
• Breast cancer
• Leukemia
• Lymphoma

The most common cause of radiation-related pneumonitis, however, is the whole-body type of radiation needed to prepare a person for a bone marrow transplant.

Aspiration
Aspiration occurs if you inhale foreign matter into your lungs. Stomach contents, such as ingested food or liquid, can sometimes cause pneumonitis.

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.

Medical procedures

• Surgical anesthesia. Undergoing general anesthesia relaxes your throat muscles and increases your risk of inhaling stomach contents. That's why people need to fast for a number of hours before receiving general anesthesia.
• 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.

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
• Information about medical problems you've had
• Information about the medical problems of your parents or siblings
• All the medications and dietary supplements you take, including over-the-counter medications — especially a stool softener such as mineral oil
• 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?
• Does anything make your symptoms better or worse?

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 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) scan. 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.

Blood tests
Your doctor may order blood tests that will check the status of your overall health. Blood tests can also be helpful in diagnosing farmer's lung.

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 painlessly clamped onto 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. Your doctor will spray an anesthetic in the back of your mouth and throat and will give you medication through a vein in your arm to help you relax.

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 biopsy a sample of cells from the lung tissue.

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.

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, 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.
• 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 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 want to consider giving it up altogether.