"Pneumonitis" is a general term for lung inflammation. It may be caused by exposure to environmental substances (allergens), certain medicines, chest radiation therapy, or inhaling acidic stomach contents (aspiration).

Pneumonia is an infectious condition caused by a germ invading the lung tissue and causing injury. Like pneumonitis, pneumonia has different causes—for example, viral, bacterial, or fungal pneumonia or aspiration pneumonia (a bacterial lung infection that occurs after inhaling stomach contents).  

This article will review the differences between pneumonitis and pneumonia, including their underlying biologies, complications, risk factors, and treatments. 

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Inflammation in Pneumonitis vs. Pneumonia

There are several types of pneumonitis, depending on the substance that you inhale or are exposed to. While some experts might consider pneumonia a type of pneumonitis because it causes lung inflammation, it's crucial to understand that pneumonia is an infectious process, whereas pneumonitis is a noninfectious one.

Symptoms of Pneumonitis vs. Pneumonia

Pneumonitis and pneumonia can cause acute (sudden and short-term) or chronic (persistent and long-term) symptoms and complications.

Acute Symptoms

Acute pneumonitis symptoms may include:

Acute pneumonia symptoms may consist of:

  • Shortness of breath
  • Productive cough (one that brings up green or yellow mucus/phlegm)
  • Fever and/or chills
  • Fast breathing rate and heartbeat
  • Sharp chest pain with breathing deeply (pleuritic chest pain)

Keep in mind that children and older adults with pneumonia may not always exhibit the above symptoms. Less common symptoms like diarrhea, nausea, shaking chills (rigors), or confusion are sometimes more prominent. 

While most people recover well from pneumonia, those who are at high risk (e.g., those who smoke or have diabetes) have a greater risk of developing short-term complications.

These complications include:

  • A lung abscess is a collection of pus (thick fluid containing bacteria, tissue debris, and dead infection-fighting cells) in the infected lung. Persistent fever and pleuritic chest pain are common symptoms.
  • Parapneumonic effusion occurs when fluid develops between the lung tissue and the inner lining of the chest wall adjacent to the pneumonia. Pleuritic chest pain and cough with phlegm are common symptoms.
  • Acute respiratory distress syndrome (ARDS) occurs when fluid accumulates in the lungs, preventing oxygen from reaching vital organs. Symptoms include severe breathlessness and low blood oxygen levels (hypoxemia).
  • Sepsis occurs when an infection, like pneumonia, enters the bloodstream and spreads throughout the body. It's associated with low blood pressure, high heart rate, and warm, flushed skin.

Chronic Symptoms

Chronic pneumonitis develops when the initial pneumonitis is left undetected or untreated.

In addition to a persistent dry cough and trouble breathing, symptoms of chronic pneumonitis may come and go or develop slowly over months to years.

They can include:

  • Unusual tiredness
  • Loss of appetite
  • Unintentional weight loss
  • Finger clubbing (when the tissue beneath the fingernails swells, causing the nails to bulge and curve down)

Severe or persistent cases of chronic pneumonitis can lead to pulmonary fibrosis—a condition associated with non-reversible scarring (fibrosis) of the lung tissue.

Specifically, this scarring damages the air sacs (alveoli) in the lungs, which transfer oxygen to the bloodstream. Hallmark symptoms are a gradually worsening dry cough, shortness of breath, and fatigue.

Other complications of chronic pneumonitis include right-sided heart failure, respiratory failure, and possibly death.

Chronic pneumonia symptoms may include productive cough, chest pain when breathing, shortness of breath, loss of appetite, and unintentional weight loss.

Possible long-term complications of pneumonia include an elevated risk of pulmonary fibrosis and cardiovascular disease (heart and blood vessel disease).

Who Gets Pneumonitis vs. Pneumonia

Certain factors increase a person's chances of developing pneumonitis vs. pneumonia.

Risk Factors for Pneumonitis

Several possible causes of pneumonitis exist, meaning multiple substances can irritate and inflame the lungs of a susceptible person. The substances causing the inflammation help to categorize pneumonitis into different types.

These types include:

  • Bird-fancier's lung is caused by inhaling specific proteins found in bird feathers and droppings.
  • Hot tub lung is caused by breathing in the bacterium Mycobacterium avium complex (MAC), which can grow in hot tubs.
  • Farmer's lung is caused by breathing in the mold growing on hay, straw, and grain.
  • Humidifier lung is caused by breathing in the fungus growing in humidifiers, air conditioners, or heating systems.

Other types of pneumonitis include:

  • Aspiration pneumonitis is caused by inhaling acidic stomach fluid.
  • Drug-induced pneumonitis is caused by taking certain medications, like some types of chemotherapy, Cordarone/Pacerone (amiodarone), and the antibiotic Macrobid (nitrofurantoin).
  • Radiation-induced pneumonitis is caused by radiation to the chest (used to treat certain cancers, like breast or lung).

Exposure to the above substances—for example, working on a farm, being a bird breeder or veterinarian, or undergoing chest radiation—increases a person's risk of developing pneumonitis.

With aspiration pneumonitis, the risk is high in people who are unconscious, bedridden, have alcohol use disorder, or have difficulties swallowing due to conditions like Parkinson's disease or stroke.

Risk Factors for Pneumonia

Factors that increase a person's risk for pneumonia include:

Lifestyle factors like smoking cigarettes or living in crowded living quarters like nursing homes or military barracks also increase a person's risk for pneumonia.

Risk factors for aspiration pneumonia are the same as those for aspiration pneumonitis (e.g., problems swallowing) in addition to dental or gum disease.

How Pneumonitis vs. Pneumonia Appears on X-Ray

In most cases, pneumonia can be diagnosed with a chest X-ray, whereas pneumonitis requires additional tests.


With pneumonitis, the chest X-ray can be normal or exhibit nodules (dense spots), ground glass nodules (dense spots with halos surrounding them), or airway plugging.

While not an exhaustive list, other tests used to diagnose pneumonitis include:

  • A high-resolution computed tomography (HRCT) scan creates a three-dimensional (3D) image of the lungs.
  • Blood tests can detect antibodies to culprit antigens.
  • Pulmonary function tests help determine how well a person's lungs are functioning.
  • A lung biopsy is when a sample of lung tissue is removed and examined under a microscope by a pathologist.


The distinguishing features of pneumonia on a chest X-ray are called infiltrates. These white spots indicate that the alveoli are filled with pus. The accumulation of pus-filled alveoli creates a visually denser area than the surrounding lung tissue—this area is called a consolidation.

Certain pneumonia complications can also be seen on a chest X-ray. For example, a lung abscess, which may occur with aspiration pneumonia, appears on a chest X-ray as an irregularly round cavity (space) with both a liquid and gas component.

Treatment Variations Between Pneumonitis vs. Pneumonia

The treatment of pneumonitis varies on the type but generally consists of avoiding the offending allergen or drug. Sometimes, corticosteroids (drugs that calm the immune system) are prescribed.

For aspiration pneumonitis, aggressive pulmonary care is vital to protect the lungs as they heal and prevent further aspiration. Strategies may include:

  • Suctioning to remove fluids/mucus in the nose and throat
  • Placing a person on a breathing machine (mechanical ventilation)

The treatment of pneumonia depends on the germ causing the infection. Antibiotics are prescribed for bacterial infections, while antifungal drugs are prescribed for fungal infections.

The treatment plan for pneumonia also includes getting lots of rest, drinking fluids, and controlling fever.

Keep in mind that while most cases of pneumonia can be managed at home, severe or chronic forms may require hospitalization for oxygen therapy and medications and fluids given intravenously (within a vein).


There is no definitive way to prevent pneumonitis or pneumonia. That said, you can take steps to be healthy and hopefully avoid these conditions.

Regarding pneumonitis, you can:

  • Ensure thorough cleaning and maintenance of hot tubs, humidifiers, heating systems, and air-conditioners.
  • Promptly repair any water damage within your home or working environment.
  • See a healthcare provider for regular checkups and report any symptoms immediately if you have a history of radiation or are taking a potential culprit drug.

Regarding pneumonia, you can:

  • Wash your hands frequently and maintain keep your vaccinations up-to-date, especially the pneumonia vaccine, COVID-19 vaccine, and flu vaccine.
  • Avoid smoking and boost your immune system by eating nutritiously and staying active.
  • Under the guidance of treating healthcare providers, control underlying medical conditions that put you at risk, including asthma and diabetes.


Pneumonitis is lung inflammation that may be caused by exposure to naturally occurring substances in the environment, certain drugs, radiation therapy, or aspiration (inhalation of acidic stomach contents).

Common symptoms include cough and shortness of breath, and treatment depends on the type of pneumonitis (e.g., avoiding the offending substance/drug, corticosteroids, or aggressive pulmonary care).

Pneumonia is a lung infection caused by a germ invading and injuring the lung tissue. Aspiration pneumonia is a type of bacterial pneumonia caused by breathing in stomach contents.

Common symptoms include a cough that brings up green or yellow phlegm and shortness of breath. As with pneumonitis, with pneumonia, treatment depends on the type of pneumonia you have, for example, antibiotics for bacterial pneumonia. Rest and fluids are also essential components of the treatment plan.

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