Pneumonitis refers to inflammation of the lungs. It is an immune system disorder that happens when an allergic reaction occurs in the lungs after inhaling certain substances.

Pneumonitis, also known as hypersensitivity pneumonitis (HP), is when an allergic reaction causes inflammation in the air sacs in one of both lungs.

The most common cause is repeated inhalation of certain allergens. Over 300 substances have been linked to pneumonitis and most of them are natural, such as mold and animal dander.

In this article, we take a look at the symptoms, causes, and treatments of pneumonitis.

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There are two types of pneumonitis, which are classified based on the duration, severity, and presentation of symptoms.

Acute HP is when symptoms appear 4-6 hours after being exposed to an allergen for a short, but intense, period of time. Symptoms may include:

Symptoms of acute HP typically go away after 1-2 days of avoiding the allergen.

Chronic HP is caused by repeated exposure to an allergen.

Around 5% of people with acute HP will develop chronic HP, which may also present the following symptoms:

It is important to get medical attention if a person has pneumonitis, as long-term lung damage may be life-threatening. For example, pulmonary fibrosis may stop the lungs from working properly and could reduce the amount of oxygen reaching the bloodstream.

Pneumonitis tends to occur when an irritating substance of any kind is introduced to the lungs. When this happens, tiny air sacs in the lungs become inflamed, making it difficult to breathe.

The causes behind pneumonitis vary and may include:

  • exposure to molds and bacteria
  • radiation treatment, usually when targeting the chest area
  • drugs and antibiotics, including some used in chemotherapy or to control the heartbeat
  • exposure to birds, bird feathers, or excrement

In most cases, the irritants that cause pneumonitis are never identified.

That said, some common irritants are associated with specific types of pneumonitis conditions, such as:

  • farmer’s lung
  • bird or pigeon fancier’s lung
  • humidifier lung
  • hot tub lung
  • cheese workers lung
  • bagassosis
  • mushroom workers lung
  • malt workers lung

The biggest risk factor associated with pneumonitis is a person’s environment.

The following groups of people have a higher risk of developing pneumonitis:

  • farmers
  • people who breed animals or birds
  • bird owners or handlers
  • veterinary workers
  • grain, wine, and flour processors
  • woodworkers

That said, only 5-15% of people working in these occupations develop pneumonitis.

Other risk factors associated with pneumonitis include:

  • lifestyle habits, such as smoking
  • genetics
  • age, as it usually affects people aged 50-70

Someone should see a doctor if their symptoms of acute HP do not go away after two days, or they worsen and become severe. In particular, any flu-like symptoms or signs of water in the lungs should be referred to a doctor immediately.

Pneumonitis may cause permanent damage to the lungs if it is not treated early. As a result, it is best to see a doctor before symptoms become severe or impossible to treat with self-care.

Pneumonitis causes similar symptoms to many other lung conditions. As such, it may take several tests before a definitive diagnosis is made.

A doctor will carry out a medical history and physical examination to establish whether the person has come into contact with any of the common substances that may cause pneumonitis.

Then, they may also request other tests, including:

To examine the lungs and collect samples of tissue or fluid, a doctor may use a device called a bronchoscopy.

This thin, flexible tube can be passed down the throat into the lungs. It has a light and a camera attached to it, allowing the user to look inside the lungs.

The first line of treatment for pneumonitis is to avoid the irritant that caused it. In cases of acute HP, this may be enough for the lungs to recover.

However, this may not always be possible for chronic HP, especially if the cause is related to chemotherapy or radiation treatments.

To help treat chronic HP, a doctor may prescribe medications to help reduce inflammation, such as:

In severe cases of permanent lung scarring, a lung transplant may be required.

Pneumonitis is largely prevented by avoiding the irritants that can cause the condition.

Taking preventative measures when dealing with irritants may help, such as wearing a face mask when dealing with birds, bacteria, or mold of any kind, or avoiding chemical irritants as much as possible.

Routine checking that heating, air-conditioning, and ventilation units are clean and working properly may also help prevent airborne irritants from causing pneumonitis.

Other lifestyle habits that may help prevent pneumonitis include:

Pneumonitis is a general term that describes inflammation in the lungs. When the inflammation is noninfectious, doctors typically refer to the problem as pneumonitis.

Pneumonia is a kind of pneumonitis because it causes lung inflammation.

That said, pneumonia is caused by a bacterial, fungal, or viral infection. As a result, pneumonia can be spread from person to person, while pneumonitis can not.

What is the main cause of pneumonitis?

Pneumonitis is an inflammatory lung condition that is caused by an allergic reaction to an environmental substance. There are over 300 allergens associated with pneumonitis. However, people most at risk of developing pneumonitis are those who are exposed to chemical irritants, work on farms or interact with birds and animals on a regular basis.

What are the early signs of pneumonitis?

The first signs of pneumonitis are flu-like symptoms, such as:

  • fever
  • chills
  • headache
  • cough
  • fatigue

Is pneumonitis serious?

Pneumonitis is a rare inflammatory lung condition. Most acute cases will resolve on their own if a person avoids the irritant that triggered symptoms in the first place. However, if left untreated, people may experience chronic cases of pneumonitis. This may have life-threatening complications, such as permanent lung scarring.

Pneumonitis can lead to severe complications if it is not treated, so people should be aware of the symptoms.

Fortunately, someone should be able to prevent the condition if they are aware of what substances could cause them to have an allergic reaction.

If anyone is experiencing the symptoms of pneumonitis and notices them getting worse at any point, they should contact their doctor.