What Is Eosinophilic Asthma?

Reviewed by: HU Medical Review Board | Last reviewed: January 2023

Less than 10 percent of people with asthma have severe asthma. Severe asthma is hard to control with inhaled corticosteroids and other treatments. A common type of severe asthma is "eosinophilic asthma."1,2

Eosinophilic asthma is caused by high levels of certain immune cells called eosinophils. High eosinophil levels can cause airway inflammation. Having an inflamed airway can lead to asthma symptoms and asthma attacks.3,4

What does eosinophilic asthma mean?

Eosinophilic asthma is a type of severe asthma. Symptoms are hard to control, even with strong medicines.2,4

Severe asthma causes heavy physical, emotional, and social burdens. Your symptoms may be frequent and hard to predict. They can interfere with your daily activities. And the side effects of asthma drugs can be significant.2,4

Eosinophilic asthma usually starts in adulthood. It can be either allergic or nonallergic asthma. This means that allergens may or may not trigger symptoms. It is often linked to chronic (long-term) sinus disease and nasal polyps.2,5

What causes eosinophilic asthma?

Doctors do not know why certain people develop this type of asthma. We do know it is caused by high levels of eosinophils. Eosinophils are a type of white blood cell that helps fight infections. Too many of them can lead to inflammation around the body.3

In eosinophilic asthma, eosinophil levels are too high in the blood, lungs, and mucus. High eosinophil levels cause the airways to swell and become narrow. This makes it hard to breathe, leading to symptoms of asthma.4,5

How is eosinophilic asthma diagnosed?

If your asthma symptoms are hard to control, your doctor may check to see if you have severe asthma. They may have to first confirm you have asthma and not another condition.2

This is an important step because severe asthma can look like other conditions. For example, eosinophilic asthma can be confused with chronic obstructive pulmonary disease (COPD).2

To confirm you have asthma, doctors will use a combination of:2

  • Symptom history
  • Overall health history
  • Physical exams
  • Lung function tests, such as spirometry

If your doctor suspects you have eosinophilic asthma, they may order more tests, including:2

  • Blood, mucus, or saliva tests to count numbers of eosinophils
  • Testing your breath for exhaled nitric oxide gas
  • Allergy testing

Your doctor will also check whether other things are making your asthma symptoms hard to control. These things can include:2

  • Using your inhaler incorrectly
  • Using your asthma drugs too often or not often enough
  • Other conditions that also cause problems with breathing
  • Risk factors and triggers, such as ongoing exposure to smoke
  • Side effects from medicines you take

If any of these things are making your asthma harder to control or worsening your symptoms, your doctor will try to find ways to help you make changes. You may try each change for a few months. If your symptoms are still uncontrolled, your doctor may refer you to a specialist to diagnose severe asthma.2

How is eosinophilic asthma treated?

Treatment for eosinophilic asthma begins with the same techniques used to manage all types of asthma. These include:2,4,5

  • Avoiding triggers
  • Using quick-relief medicines such as short-acting beta agonists
  • Using daily control medicines such as inhaled corticosteroids

But typical asthma treatments often do not work well for people with eosinophilic asthma. Your doctor may suggest adding a targeted biologic drug to your treatment. Each of these drugs targets a specific protein that contributes to severe asthma. Some examples include:2,3

  • Nucala® (mepolizumab)
  • Fasenra® (benralizumab)
  • Cinqair® (reslizumab)
  • Dupixent® (dupilumab)
  • Tezspire® (tezepelumab-ekko)

Blocking these proteins lowers the number of eosinophils. Xolair® (omalizumab) is another biologic. It is useful for some types of severe allergic asthma. But it is not useful for eosinophilic asthma.2,5

If you have asthma, talk to your doctor about creating an asthma action plan.

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