What is Eosinophilic Pneumonia?


Eosinophilic pneumonia is a rare inflammatory condition that affects your lungs. It is due to an abnormal level of eosinophils (a type of white blood cell) that causes inflammation and subsequently damage to your lung tissue. 

To understand eosinophilic pneumonia (“e-oh-sin-oh-fi-lic new-mo-nia”), we can break down the name. Eosinophilic refers to a higher than normal number of eosinophils, an immune cell in your body, and pneumonia is an inflammatory lung condition resulting from pathogens (germs that cause disease). From this, we can understand that pneumonia develops in the lungs due to this excess amount of eosinophils.

This article will go into depth about the types, causes, symptoms, and treatment of eosinophilic pneumonia, so read on to learn more.

What are eosinophils?

Eosinophils are one of the many types of white blood cells involved in the immune response to protect the body from foreign particles. Eosinophils make up approximately 1-4% of white blood cells on average, but this percentage can increase during inflammation. 

The immune system is large and complex, but eosinophils are involved in allergic reactions, parasitic infection defence, and chronic inflammation.1 When activated by the signs of a foreign pathogen in the body, eosinophils release signalling chemicals that help fight this and destroy unhealthy cells. 

However, in certain diseases, eosinophils can cause excess inflammation in the body. An excess build-up of eosinophils is a condition called eosinophilia. Eosinophilic pneumonia occurs following eosinophilia.

Eosinophilic pneumonia is an overarching term for a group of lung disorders that are characterised by elevated levels of eosinophils in the blood as well as either the lung tissue or bronchoalveolar lavage fluid (from a diagnostic technique where the airways are ‘washed’).

Types of eosinophilic pneumonia

Eosinophilic pneumonia is categorised as a primary eosinophilic disorder and can further be diagnosed as acute or chronic eosinophilic pneumonia, or Loeffler’s syndrome.

Acute eosinophilic pneumonia

This type progresses quickly within 2 weeks and has an intense onset of symptoms. It is characterised by eosinophils invading the:

  • Alveoli - the tiny air sacs in the lungs
  • Bronchial walls - your windpipe divides into two bronchi, airways that go into each lung
  • Interstitium (less common) - support tissues within the lungs, such as protective membranes

Damage to the alveoli is present in chest X-rays.

Chronic eosinophilic pneumonia

This type progresses more slowly over days and weeks but can become just as severe. It can often reoccur and develop into life-threatening symptoms if not treated

Loeffler’s syndrome

This type of eosinophilic pneumonia is due to a parasitic infection in the lungs. This condition can have mild to no symptoms and patients usually recover within 2 weeks after diagnosis.

Symptoms of eosinophilic pneumonia

All three types of eosinophilic pneumonia have a similar set of symptoms that may range based on severity. The most commonly reported symptoms are:

  • Consistent coughing
  • Dyspnea -  the feeling of running out of air
  • Fever 

Some less common symptoms include:

  • Malaise - a feeling of discomfort, sickness, or uneasiness
  • Myalgia - muscle aches and pains
  • Night sweats
  • Chills
  • Pheuritic chest pain - sharp pain in the chest when breathing deeply

Causes of eosinophilic pneumonia

This increase of eosinophils in the lung can be attributed to either an infectious or a non-infectious cause

Infectious causes of eosinophilic pneumonia are due to parasites. Some of these include:

Non-infectious causes of eosinophilic pneumonia include:

  • Environmental triggers, such as allergies
  • Tobacco smoking
  • Asthma
  • Pharmaceutical drugs, such as penicillin
  • Toxins, such as chemical fumes
  • Malignant tumours
  • Allergic bronchopulmonary aspergillosis - a reaction to a type of fungus in the airways
  • Can sometimes occur without triggers spontaneously

A study suggested that the highest percentage causes of eosinophilic pneumonia are smoking-related at 31% and medication-related at 17%.2 It is commonly understood that tobacco smoke can cause a plethora of health issues, not only in your lungs but nearly every organ. Regular smoking causes inflammation and damage throughout your entire body.

Management and treatment for eosinophilic pneumonia

Depending on the severity, type, and cause of eosinophilic pneumonia, the treatment can vary. In mild cases, some patients may recover without any interventions. 

If the eosinophilic pneumonia is attributed to a non-infectious cause, such as a pharmaceutical drug or smoking, ceasing this can alleviate the symptoms and prevent a relapse of the disorder.

In moderate to severe cases, glucocorticoids (a type of steroid hormone) and supplemental oxygen may be administered to manage symptoms. Glucocorticoids are used for inflammatory or autoimmune diseases to help to suppress the immune system. 

Often, it is best to administer glucocorticoids as soon as possible to see improvement within 12-48 hours. This treatment has been shown to be extremely efficient in resolving the symptoms within hours and eosinophil levels recover completely within a month. 

For chronic cases, longer treatment with a glucocorticoid may be required for up to 9 months.

Without treatment, there is a chance of progressive respiratory failure. This is when your lungs cannot oxygenate the blood. This is dangerous and can potentially lead to death. It is best to treat eosinophilic pneumonia before this occurs, but recovery is still possible with corticoids.


Before any testing is done, a medical history will be taken to suggest any cause associated with eosinophilia.

Diagnosis of eosinophilic pneumonia can be done through an eosinophil blood test and in some cases, a biopsy of the lung to check if they have infiltrated the lung tissue. A biopsy is a surgical procedure where a doctor takes a small chunk of lung tissue to analyse. In this case, they can slice and stain the tissue, looking for the immune cells.

In acute eosinophilic pneumonia, chest imaging is done on patients with progressively worsening respiratory symptoms to check for infiltration of immune cells in the lung tissue. For a diagnosis of acute eosinophilic pneumonia, the patient must have an eosinophil count above 25% in bronchoalveolar lavage fluid. 

A biopsy may not be required for diagnosis but may be done if there are conditions that suggest an alternative diagnosis.2 Additional testing may be done to exclude other disorders related to eosinophilia.

There are many types of tests that can confirm the type and severity of eosinophilic pneumonia. To be able to confidently diagnose this disorder rather than disorders with similar symptoms, your doctor or specialist will recommend some of the following tests:

  • Bronchoalveolar lavage - collecting a sample from the lungs by washing the airways with a solution to test for eosinophils and the pH
  • Blood test for complete blood count
    • Serum IgE elevation - elevated IgE (a type of antibody) indicates an allergic reaction
    • Iron levels
  • Checking for fluid in the area between the lungs and chest wall
  • Pulmonary function test - this tests how well the lungs are working
  • Chest X-ray to look at the structure of the lung
  • Erythrocyte sedimentation rate blood test - if the rate is elevated, this can be attributed to inflammation


Most eosinophilic pneumonia patients make a full recovery within a month of treatment. However, without properly managing the underlying cause, eosinophilic pneumonia can develop into respiratory failure and in some cases, death. There have also been reports of relapse after glucocorticoid therapy due to tobacco smoking.


How can I prevent eosinophilic pneumonia?

While not all cases of eosinophilic pneumonia can be prevented, you may be able to avoid some common causes. One of the most common is tobacco smoke. You should avoid smoking or being around others when smoking tobacco. Tobacco is a major irritant for the body and can cause a multitude of diseases including lung cancer. 

There are other environmental irritants that can lead to eosinophilic pneumonia such as fine dust or sand, cleaning gasoline tanks, woodpile moving, and renovating buildings to name a few. In these cases, you should take proper precautions to protect your lungs such as adequate face coverings.2

Who is at risk of eosinophilic pneumonia?

Eosinophilic pneumonia can happen at any age or gender. Chronic eosinophilic pneumonia is most commonly seen in those of Caucasian descent, assigned female at birth, and between the ages of 30-40, and asthma is present in 50% of cases. Acute eosinophilic pneumonia is more commonly seen in those assigned male at birth between the ages of 20-40.3 

When should I see a doctor?

Seek urgent medical care if you experience any symptoms listed earlier in the article, particularly if you are experiencing shortness of breath or chest pain.


Eosinophilic pneumonia is an inflammatory lung condition caused by an abnormal amount of eosinophils, a subcategory of white blood cells. The causes of this disease can be infectious from a parasite or non-infectious causes, such as environmental toxins, preexisting lung disorders, or it can happen without a known cause. 

Symptoms often include a persistent cough, fever, and breathlessness. If you think you may have eosinophilic pneumonia, your doctor will take a full medical history and blood sample for initial testing. Following this, they may recommend seeing lung specialists for a chest X-ray and a lung function test to confirm the diagnosis. 

In most mild cases, eosinophilic pneumonia can clear up without medical intervention. Treating acute and chronic eosinophilic pneumonia usually involves early administration of a glucocorticoid to suppress the inflammation. In severe cases, oxygen supplementation may be given. 

It is important to talk to your doctor to understand the cause of your eosinophilic pneumonia to prevent further relapses of this disorder.

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sara Nakanishi

Master’s of Science - Genes, Drugs, and Stem Cells - Novel Therapies, Imperial College London

Bachelor of Science - Biochemistry/Chemistry, University of California San Diego

Hello! My name is Sara and I have a diverse background in science, particularly in biochemistry and therapeutics. I am extremely passionate about heart health and mental illness. My goal is to break down complex scientific topics to share with those with non-scientific backgrounds so they can be well-informed about their conditions and ways to live a balanced life. I believe that education and awareness are key to leading a healthy lifestyle and I hope to inspire others through my writing.

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