What is Eosinophilic Asthma

Eosinophilic asthma is a subtype of asthma that is often severe. It is sometimes called eos asthma or e-asthma. Eos asthma can cause persistent asthma attacks and breathing problems that includes coughing, wheezing and shortness of breath.

Many adults who develop asthma later in life have eos asthma. However, young adults and children can also get the condition.

Eosinophilic asthma is a form of asthma driven by a Type 2 (Th2) immune response. Type 2 refers to an immune-based form of asthma where your body’s immune responses (certain cells and signals) cause inflammation (swelling) in the airways.

Eosinophilic asthma is characterized by:

  • High levels of eosinophils (ee-oh-SIN-oh-fills), which are white blood cells
  • Inflammation (swelling) in the lungs
  • More serious or harder-to-control asthma symptoms, even when using asthma treatments such as inhaled corticosteroids
Labeled diagram of an eosinophil cell showing cytoplasm, primary granule, mitochondria, Golgi apparatus, lipid bodies, sombrero vesicles, and a bi-lobed nucleus; logos at the bottom.

Eosinophilic asthma severity

Asthma is a chronic (long-term) lung disease. It causes inflammation (swelling) in the airways of the lungs. This chronic inflammation can cause:

  • Increased mucus in the airways
  • Wheezing
  • Coughing
  • Shortness of breath
  • Chest tightness

If you have uncontrolled asthma, symptoms can become dangerous if not treated. They can lead to an asthma attack.

A person stands against a light brick wall. Text reads: "10% of all asthma is categorized as severe." Logos for EOS Asthma Toolkit, Allergy & Asthma Network, and APFED are at the bottom.

People with eosinophilic asthma often have more frequent or severe symptoms that are harder to manage with regular asthma medications.

What is severe asthma?

When asthma is severe, it means a person’s symptoms do not get better, even with consistent treatments or high-dose controller medicines. People with severe asthma have long-term inflammation that is hard to treat. It is common for people with severe asthma to also have a history of having needed oral or injectable corticosteroids to treat their condition.

When diagnosing asthma, doctors look for what might be causing it. This can be from immune cells or specific triggers:

  • Eosinophilic Asthma: Characterized by high levels of eosinophils
  • Non-eosinophilic Asthma: Such as neutrophilic asthma, which involves different immune cells (neutrophils)
  • Allergic (IgE-mediated) Asthma: Often triggered by allergens like dust mites, pet dander, or pollen
Infographic about eosinophilic asthma, highlighting increased eosinophils in the respiratory tract, airway obstruction, and frequent sinus disease or nasal polyps. Includes icons of lungs, airflow blockage, and sinus pain.

Role of eosinophils in asthma

Eosinophils are white blood cells that help fight certain infections. They are involved in multiple medical conditions. Too many eosinophils can cause long-lasting swelling in the airways. This process is called eosinophilic airway inflammation.

In people with eos asthma, increased eosinophils can be found in the blood, lung tissue, and in sputum (the mucus you cough up). When the mucus has too many eosinophils (called sputum eosinophilia), it can block air coming in and make asthma symptoms hard to control. It can affect the entire breathing system from the nose down to the small airways in the lungs.  

Research shows that people with high eosinophil counts in their blood have a higher risk of future asthma attacks and more severe symptoms.

Eosinophilic asthma symptoms

People with eosinophilic asthma often have:

  • Wheezing: a whistling sound when breathing.
  • Coughing: occurring especially at night.
  • Shortness of breath: trouble breathing even during simple everyday activities like going up the stairs.
  • Chest tightness: a feeling of pressure or squeezing.
  • Extra mucus: thick fluid in the airways.
  • Lung function problems: when tests show that air moves slowly through your lungs.
  • Inflamed nasal lining.

Doctors may also look for:

  • Nasal polyps: small growths inside the nose.
  • High eosinophil counts: in blood or sputum samples.
  • High exhaled nitric oxide: a gas that is seen with airway swelling.

Comorbidities: other conditions linked to eosinophilic asthma

People with eosinophilic asthma often have other related health conditions (comorbidities). Managing these conditions is important because they can make asthma symptoms worse or harder to treat.

Common comorbidities include:

  • Nasal polyps. Also related to chronic rhinosinusitis with nasal polyps (CRSwNP). These are small, non-cancerous growths inside the nose that can block airflow and increase inflammation. They’re common in people with eos asthma.
  • Aspirin-exacerbated respiratory disease (AERD). Some people with eos asthma have a severe reaction when they take aspirin or similar pain relievers.
  • Asthma-COPD Overlap (ACO). This is when someone has both asthma and chronic obstructive pulmonary disease (COPD). It can lead to worse symptoms and difficulty managing asthma.
  • Fungal sensitization. Some people with eos asthma have an allergic-type reaction to fungi or mold in the environment, which can make symptoms worse.
  • Obesity. Carrying extra weight can increase inflammation, making it harder to manage asthma. 

If you have any of these conditions, talk to your doctor. Proper treatment can help improve your asthma control and your quality of life.

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Are there different types of eosinophilic asthma?

Eosinophilic asthma is a phenotype of asthma. A phenotype is a set of traits that make one disease type different from another. Even if there is only one type of eosinophilic asthma, it can differ from person to person. Some people have allergies with asthma, while others do not. Symptoms can also vary in how severe or frequently they occur.

Some people with eos asthma may not get better when using high doses of inhaled corticosteroids. In these cases, other treatments such as biologic medicines may be needed to control their asthma.

What is eosinophilic asthma vs. allergic asthma?

Eosinophilic asthma and allergic asthma are two kinds of asthma. They both involve the immune system, but they often have different triggers and symptoms.

Eosinophilic asthma is caused by too many eosinophils, a type of white blood cell that causes swelling in the airways. It’s not usually triggered by common allergens like pollen, mold, dust mites or pet dander. Some people with eos asthma also have allergic asthma, allergic rhinitis and/or eczema.

Allergic asthma is a type of asthma that’s triggered by allergens — pollen, mold, pet dander, dust mites, cockroaches and mice. When people with allergic asthma inhale these allergens, their immune system treats them like a threat and releases chemicals such as histamine. The chemicals cause swelling in the airways and other allergy symptoms like itching, sneezing or a runny nose.

Knowing the type of asthma you have can help your doctor provide a personalized treatment plan.

Causes of eosinophilic asthma

While the exact cause is still being studied, current research shows about 50% of people with severe asthma have eosinophilic asthma.

Some people have high eosinophils in their airways without any clear cause. Others find that irritants, like smoke or strong smells, lead to flares. Certain infections might also play a role.

Doctors believe a mix of things can cause eosinophilic asthma to develop, including:

  • Genetics. Certain genes can raise the chance of having high eosinophil levels or type 2 inflammation.
  • Environmental factors. Irritants like smoke, strong smells, pollutants, allergens, and respiratory infections can trigger flare-ups.
  • Other factors. Psychological stress and even obesity can play a role.
A doctor speaks with a concerned young woman who is touching her chest. The doctor holds a medical device and gestures reassuringly, suggesting a medical consultation or examination is taking place.

How common is eosinophilic asthma?

  • About 10% of all asthma cases are classified as severe.
  • Approximately 50% of severe asthma is eosinophilic.
  • Eosinophilic asthma is most often diagnosed in adults aged 35–50, though it can also be seen in older adults and children.
  • Unlike some asthma types, eosinophilic asthma affects males and females equally.

Can you live a long life with eosinophilic asthma?

Most people with eosinophilic asthma can lead a long and normal life with the right management plan. Eos asthma is a chronic condition that does not go away over time. But regular treatment and checkups can keep symptoms under control. Even if you sometimes feel better and have few or no symptoms (remission), the condition can still be present.

Key tips include:

  • Follow your treatment plan. Take your medicines as prescribed and see your doctor regularly.
  • Avoid triggers. Stay away from smoke, strong fumes, and other irritants.
  • Develop healthy habits. Stay active, eat well, and manage stress.
  • Advanced treatments. For those with uncontrolled asthma, new biologic treatments may help.

Uncontrolled asthma can be scary and make it hard to go to school, work, or do everyday activities. That’s why it’s important to manage your asthma effectively.

Questions and answers (Q&A) about eosinophilic asthma

Eosinophilic asthma is a severe form of asthma. It may require more advanced treatments. You may need to see an asthma specialist such as a board-certified allergist or pulmonologist. Here are some common questions we’re asked about eosinophilic asthma along with their answers. If there’s a question you feel should be added, please email our editor.

Common physical signs include wheezing, coughing, shortness of breath, chest tightness and increased mucus. Doctors also look for high eosinophil counts in blood or sputum (mucus) and changes in lung function tests that point to airway swelling. They will also look for nasal polyps, which are small noncancerous growths in the nose.

Standard or “regular” asthma can flare up for many reasons, such as due to a respiratory virus, exercise or allergens like pollen or mold. This type of asthma is often treated with inhaled medications, including a quick-reliever and a daily controller.

With eosinophilic asthma, there are too many eosinophils (white blood cells) in the breathing tubes. These extra cells cause increased airway inflammation, making breathing even harder than in most other types of asthma. People with eosinophilic asthma often need stronger and more advanced medicines, beyond the inhalers for standard asthma.

Eosinophilic asthma is not an autoimmune disease. An autoimmune disease is when the body attacks its own healthy parts. In eosinophilic asthma, symptoms are caused by having too many eosinophils (white blood cells that should fight germs). This leads to increased inflammation in the airways.

When a patient has severe asthma, doctors may look to see if a certain type of white blood cell is causing swelling in the lungs. There are two main types of white blood cells that can affect asthma: eosinophils and neutrophils.

Neutrophilic asthma is caused by high levels of neutrophils. This type is harder to treat with standard asthma medications but it does respond to certain biologics.

Eosinophilic asthma is caused by too many eosinophils. These cells lead to inflammation, making it hard to breathe. This type usually responds well to inhaled corticosteroids and biologic medicines. 

There is no way to fully lower eosinophils naturally and without treatment. However, these tips may help reduce overall swelling and improve your asthma control:

  • Stay active. Exercise helps the lungs work better.
  • Avoid smoke. Cigarette smoke and strong fumes can trigger attacks.
  • Manage stress. Stress can worsen asthma symptoms. Techniques like deep breathing or relaxation help you stay calm.
  • Eat a balanced diet. Fruits, vegetables, and lean protein support health.
  • Get enough sleep. Good rest may help prevent flare-ups.

Even with these steps, you may still need asthma medications to control eos asthma.

Eosinophilic asthma can be triggered by many of the same things that affect allergic asthma, but also non-allergic triggers. Common ones include:

  • Respiratory infections, like a cold or the flu
  • Allergens, like dust mites, pollen, mold, or pet dander
  • Air pollution, smoke, or strong smells
  • Cold air or sudden changes in weather
  • Exercise, especially in cold or dry air
  • Stress

Sometimes there are no clear triggers. Some people with eosinophilic asthma don’t react to anything specific. Their immune system becomes overactive for reasons doctors don’t always fully understand. Even without known triggers, eosinophilic asthma can still cause serious symptoms.

Uncontrolled comorbidities, such as chronic sinus disease or nasal polyps, may also play a role. Research shows these factors can cause airway inflammation without the typical allergy (IgE) response seen in allergic asthma.

Work with your doctor to learn what affects your asthma. Avoiding your triggers and taking your medications as prescribed can help keep your asthma under control.

Many options are available to treat eosinophilic asthma. It will depend on the level of asthma severity.

Some people with asthma respond well to traditional medications, such as a quick-relief albuterol inhaler and a daily controller medication like inhaled corticosteroids. Inhaled corticosteroids are sometimes combined with long-acting beta-agonists in a single inhaler to help people with severe asthma. Other medications include leukotriene modifiers that block chemicals that start airway inflammation.

If these medications do not work for severe asthma patients, then your doctor may recommend biologic treatments. These are advanced medications designed to treat moderate to severe asthma with an eosinophilic phenotype. Multiple biologics are available, each designed to target eosinophils and reduce or control their levels.

Talk with your doctor about which medication is right for you.

“EOS” is short for eosinophils. These are white blood cells. When eosinophil levels are high in the blood or mucus, it can be a sign of eosinophilic airway inflammation.

Yes, genetics can play a part in the development of eos asthma. Some families pass down genes that make high eosinophil levels or Type 2 inflammation more likely.

Not everyone with eosinophilic asthma has a family history of the condition, though. Environmental factors like irritants, infections or stress can also contribute to eos asthma.

Severe eosinophilic asthma is asthma that is hard to control even when taking prescribed treatments. People with severe eos asthma tend to have ongoing symptoms and frequent asthma attacks that make it hard to do everyday activities. These patients may need more advanced treatments such as biologic therapies.

Eosinophilic asthma is a chronic, long-term condition that does not typically go away. Some people may experience periods where they have few or no symptoms, but the disease can come back. Regular checkups, taking medications as prescribed, and following the treatment plan can help keep eosinophilic asthma under control.

The 4 levels of asthma refer to how often asthma symptoms happen and how serious they are. The levels are intermittent, mild persistent, moderate persistent and severe persistent.

Severe persistent asthma involves symptoms most of the time, frequent intense flare-ups, and major limits on daily life.

Intermittent asthma occurs less than twice a week with rare flare-ups. 

Mild persistent asthma happens more than twice a week but not every day. Sometimes causes night-time awakenings. 

Moderate persistent asthma brings daily symptoms that can affect everyday activities, plus more frequent night-time flare-ups. 

Yes, a severe attack can be life‑threatening if medical help is not given quickly. About 10 people a day from the disease. It’s important to keep your quick-relief inhaler with you at all times and use it at the first sign of symptoms. Follow your Asthma Action Plan and call 911 if you are still struggling with breathing after using quick-relief medicine.

Reviewed by:
William E. Berger, MD, FACAAI, is a board-certified allergist and immunologist who serves as a media spokesperson and Chair of the Medical Advisory Council for Allergy & Asthma Network. He is a Distinguished Fellow and Past President (2002-03) of the American College of Allergy, Asthma & Immunology (ACAAI).

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