Eosinophilic Asthma: Causes, Symptoms, and Effective Treatments
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What Is Eosinophilic Asthma? Diagnosis, Causes, Complications, and Treatment

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Published on January 7, 2025
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There are different types of asthma, including allergic, nonallergic, and exercise-induced. Eosinophilic asthma (also called eos asthma) can happen if you have high levels of eosinophils, a type of white blood cell, in your airways.


Eos asthma is classed as a severe asthma and can result in long-term airway damage.

Eosinophils help your body fight infection. But if too many are present in your airways they can overreact, leading to swelling and other asthma symptoms. The symptoms may be more severe than with other types.

According to the Asthma and Allergy Foundation of America (AAFA) 10 percent of people with asthma in the United States have severe symptoms that are hard to manage. Many of these people, they say, may have eosinophilic asthma.

People with asthma don’t always know if it’s eos asthma or not, as an episode can have the same triggers as other types of asthma, and symptoms can be similar. Your doctor can find out by doing tests.

What Is Eosinophilic Asthma?

Asthma is a condition in which airway inflammation makes it hard to breathe. This can result from allergic and nonallergic causes.

“Asthma is characterized by airflow obstruction and limitation of airflow that’s associated with inflammation,” says Michael Wechsler, MD, a codirector of the Cohen Family Asthma Institute at National Jewish Health in Denver. “There’s a subset of asthma patients in whom that inflammation is caused by eosinophils.”

Eosinophils are white blood cells that play an important role in the immune system. They are bigger than most cells and account for less than 5 percent of all your white blood cells.

These cells help your body fight infections, such as bacteria, parasites, and viruses. But, they can also contribute to other diseases, including asthma.


When your immune system fights a pathogen, such as an infection, you’ll notice certain reactions, such as inflammation and swelling. These reactions are a healthy and necessary part of the immune response.

But if your immune system overreacts, symptoms can occur more often and be more severe.

Present throughout the body, normally eosinophils tend to occur in high levels in certain organs, such as the gastrointestinal tract, with lower concentrations in the airways.

High levels of eosinophils in your airways can cause your immune response to be too strong, leading to severe inflammation.

As the Cleveland Clinic website explains, your airways become “clogged” with inflamed eosinophils.

Causes and Risk Factors

It’s not clear why some people have higher eosinophil levels in their airways, but they may have one or more of the following risk factors.

  • An allergic reaction
  • A parasitic disease
  • A drug reaction
  • Genetic factors
  • Stress
  • Exposure to pollutants
  • A respiratory infection
Experts believe these factors may trigger an immune response that leads to persistently high levels of eosinophils and chronic inflammation.

Usually, high numbers of eosinophils that occur during an immune response die off and leave the body when they’re no longer needed. For some reason, however, this doesn’t always happen, and levels remain high.

Eos Asthma and Other Asthma Types

Eos asthma can resemble other types of asthma, but there are also differences.

Age

Eos asthma usually appears in adults rather than children. It commonly starts at 35 to 50 years of age, but it can also affect older people and children.


Allergies

People with eos asthma may not have a history of other allergies, but exposure to environmental substances, such as dust mites, can sometimes trigger it.



Symptoms

In addition to other asthma symptoms, people with eos asthma may also have persistent inflammation in the nose and sinuses and nasal polyps.

Response to Treatment

Doctors categorize severe asthma as either type 2 or non–type 2, depending on how symptoms respond to specific treatments. Eos asthma is a type 2 inflammatory asthma, along with allergic asthma.

Type 2 asthma, such as eos asthma, responds to inhaled corticosteroids and biologic drugs. Non–type 2 asthma may not respond to these drugs.

Symptoms of Eosinophilic Asthma

The symptoms of eosinophilic asthma can resemble those of other asthma types, but there may be additional symptoms.

They include:


  • Wheezing
  • Coughing
  • Shortness of breath or breathing difficulty
  • Chest tightness
  • Airflow obstruction, affecting how well the lungs work
  • Persistent rhinosinusitis
  • Nasal polyps
  • Inflamed mucous membrane in the nose
People with high eosinophil levels in their airways may also have a risk of developing chronic obstructive pulmonary disease (COPD).

Diagnosis of Eosinophilic Asthma

To diagnose eos asthma, a doctor will likely ask about:


  • Your symptoms
  • Any history of asthma
  • Any allergies
  • Other medical history

They will also carry out a physical examination.

If the doctor suspects eos asthma, they may also do tests to see if you have high levels of eosinophils.

Tests for Eos Asthma

Three tests are used to diagnose eos asthma:

  • A blood test: A health professional will use a needle to take a small blood sample, usually in a doctor’s office. They’ll then send it to a laboratory for testing. Eosinophil levels of 150 cells per microgram (mcg) or over may be a sign of eos asthma.

  • A sputum test: You’ll need to cough up a mucus sample, usually in a doctor’s office. Your doctor will send it to a pathologist to examine under a microscope. An eosinophil count of 2 percent or higher in sputum may indicate eos asthma.

  • A bronchial biopsy: A specialist lung doctor (pulmonologist) will apply local anesthesia and put a narrow tube (bronchoscope) down your throat and into your lungs. The device will collect small samples of tissue and fluid. The doctor will examine this to see if the samples contain eosinophils. You may need to do this in a hospital.

Dr. Wechsler notes: “It’s really important for people with severe asthma to ask, 'What kind of asthma do I have? Do I have eosinophils? What is the subtype of asthma?'” He adds, “New treatments released over the past three years can help with the eosinophilic subtype.”

The right diagnosis will help you get the right treatment.

Treatment and Management of Eosinophilic Asthma

You can often manage eos asthma with a combination of the usual asthma medications and some special drugs to reduce eosinophil levels in the airways.

Common Asthma Drugs That May Help

Common asthma medications include:

  • Bronchodilators, which relax and open the airways
  • Corticosteroids and other anti-inflammatory medications
  • Options combining both bronchodilators and anti-inflammatory drugs
Some treatments are for long-term use, to prevent attacks. They include inhaled corticosteroids and long-acting beta-agonists.

Others, known as rescue medications, help manage symptoms when they arise. Rescue drugs include short-acting albuterol inhalers and oral corticosteroids.

These drugs help many people with eos asthma but not everyone.

Long-Term Drugs and Biologics for Eos Asthma

If the usual asthma drugs don’t help, your doctor may suggest other long-acting options such as leukotriene modifiers or a biologic drug.

Leukotriene Modifiers

Your body releases leukotrienes as part of the immune response. They can lead to coughing, airway inflammation, and other asthma-like symptoms.

Leukotriene modifiers block the action of leukotrienes and stop these symptoms from happening. They can help with various types of asthma.

Here are some examples:

  • montelukast (Singulair)
  • zafirlukast (Accolate)
  • zileuton (Zyflo)

Biologics

Also known as targeted therapies, biologic drugs reduce inflammation by targeting specific cells and pathways in your body. Doctors will prescribe them alongside other treatments.

Research suggests various biologics can help reduce episodes and improve lung function in people with EOS asthma.

Examples of biologics for eos asthma include:

  • benralizumab (Fasenra): Delivered as an injection, you can use this drug from the age of 12 years. It reduces inflammation by lowering eosinophil levels.
  • mepolizumab (Nucala): Also delivered as a shot, this is suitable for those 6 years and older. It reduces eosinophil levels, which decreases inflammation.
  • reslizumab (Cinqair): This intravenous drug is suitable for people with eos asthma aged 18 or above. It lowers eosinophil levels and reduces inflammation.
  • dupilumab (Dupixent): Delivered as a shot, this drug helps reduce flares in people aged 6 and over with moderate to severe eos asthma or oral corticosteroid-dependent asthma. It can also help manage severe eczema (atopic dermatitis) and chronic sinusitis with nasal polyposis.
Scientists continue to investigate new options for managing eos and other severe types of asthma.

According to Wechsler, “This treatment doesn’t necessarily eliminate attacks or exacerbations, but in some people it does, and in other people it reduces them dramatically.”

Complications of Eosinophilic Asthma

Eosinophilic asthma can lead to complications. It can also occur with or possibly increase the risk of other conditions.

Persistent inflammation with eos asthma may lead to cell changes in the airways, resulting in tissue damage, scarring, and long-term changes to airway structure. This damage may not be reversible.

Other complications or comorbidities include:

  • Nasal polyps
  • Persistent sinusitis, rhinitis, or both, known as rhinosinusitis
  • Aspirin-exacerbated respiratory disease (AERD) due to a higher sensitivity to aspirin
  • Sensitivity to other nonsteroidal anti-inflammatory drugs (NSAIDs)

Early treatment for eos asthma may reduce the risk of complications.

Living With Eosinophilic Asthma

Eosinophilic asthma can be challenging, but medication and lifestyle choices can help you manage it.

Here are some tips for living well with eos asthma:

  • Find a specialist doctor you can trust. You may need an allergist, pulmonologist, or both. The American College of Allergy, Asthma & Immunology has an allergist locator on their website to help you find specialist care, and Apfed has one for a range of specialties.
  • With your doctor, work out a treatment plan and follow it carefully. This includes finding the right medication, using it correctly, and attending follow-up visits.
  • Learn more about eosinophilic asthma. The more you know about your condition, the more in control and less anxious you'll feel. For instance, you can sign up for a newsletter from dedicated sites such as Apfed.
  • Keep a log of your symptoms and use it to pinpoint any triggers. Then do your best to avoid them.
  • Speak with loved ones or seek counseling if living with eos asthma is causing anxiety, depression, or otherwise affecting your mental well-being.
You might also consider joining a clinical trial to find new treatments for eosinophilic asthma. During a clinical trial, you’ll have access to highly specialized professionals. You may also have a chance to try new medications free or charge and before they become widely available.

The Takeaway

  • Eosinophilic asthma, also called eos asthma, is a type of asthma that can happen when you have too many eosinophils, a type of white blood cell, in your airways.
  • Eosinophils help protect the body from infections and other invaders, but too many can result in an overactive immune response and persistent inflammation.
  • This form of asthma can be severe, and treatment is essential. Early treatment can prevent long-term damage and complications.
  • Eos asthma symptoms don’t always respond to the usual asthma treatments. If so, biologic or leukotriene therapy can often help manage this condition.

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Jon E. Stahlman, MD

Medical Reviewer
Castle Connolly Top Doctor

Jon E. Stahlman, MD, has been a practicing allergist for more than 25 years. He is currently the section chief of allergy and immunology at Children’s Healthcare of Atlanta's Scottish Rite campus and the senior physician at The Allergy & Asthma Center in Atlanta. He served as the president of the Georgia Allergy Society, has been named a Castle Connolly Top Doctor, and was listed as a Top Doctor by Atlanta magazine. His research interests include new therapies for asthma and allergic rhinitis as well as the use of computerized monitoring of lung function.

He received his bachelor's and medical degrees from Emory University. He completed his pediatric residency at Boston Children’s Hospital and his fellowship in allergy and clinical immunology at Harvard University’s Boston Children’s Hospital and Brigham and Women’s Hospital. After his training, Dr. Stahlman conducted two years of clinical research at Boston Children’s Hospital and was part of the faculty at Harvard Medical School, where he taught medical students and allergy and immunology fellows.

Stahlman is board-certified and recertified in allergy and clinical immunology. He served as a principal investigator on phase 2 through 4 studies that are responsible for most of the U.S. Food and Drug Administration–approved therapies for allergies and asthma available today.

Outside of the office, he centers his interests around his wife and three daughters, coaching soccer for many years, and his hobbies include cycling and triathlons.

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Yvette Brazier's career has focused on language, communication, and content production, particularly in health education and information. From 2005 to 2015, she supported learning in the health science department of a higher education establishment, teaching the language of health, research, and other language application skills to paramedic, pharmacy, and medical imaging students.

From 2015 to 2023, Yvette worked as a health information editor at Medical News Today and Healthline. Yvette is now a freelance writer and editor, preparing content for Everyday Health, Medical News Today, and other health information providers.

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