What Is Eosinophilic Asthma (E-Asthma)?

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Eosinophilic asthma, also known as e-asthma, is one of the most common subtypes of asthma diagnosed in adulthood. Eosinophilic asthma occurs when a high number of eosinophils, a type of white blood cell, inflame the lungs. Why this occurs is unknown. Because lung samples can be difficult to obtain, elevated numbers of blood eosinophils are often used a surrogate for diagnosis in patients with difficult to control asthma. Allergic asthma is not the same as eosinophilic asthma. Eosinophilic asthma can occur in some atopic patients (meaning those patients that have a tendency toward allergies) but it can also occur without atopic predisposition.

Inflammation from eosinophilic asthma occurs as part of an allergic or immune system response, which releases a specific white blood cell called eosinophils. When you have an increase in white blood cells, you will typically have an inflammatory response, which leads to thickening of your airways. The fluid and mucus that results may lead to spasms in your airways (bronchioles) and cause your asthma symptoms.

senior woman using inhaler
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Asthma is an inflammatory disorder of the airways that can make it difficult to breathe. About one out of 13 people suffer from this chronic illness, and poor control of asthma can lead to risk for life-threatening asthma attacks.

Know that most of these exacerbations are preventable if the asthma is properly managed. While originally thought to be a single disorder, asthma actually has many subtypes that can alter how your asthma can best be controlled.

About 5% to 10% of people with asthma have severe asthma. While the prevalence of having eosinophilic asthma is relatively unknown, studies suggest that around 50% percent of cases of severe asthma are eosinophilic asthma.

If you are older than 35 when you are diagnosed with severe asthma you have a higher risk of being diagnosed with eosinophilic asthma. Your risk is the same regardless of your gender, and you have a lower risk of being diagnosed with eosinophilic asthma in your childhood and teenage years.


Many of the symptoms of eosinophilic asthma are the same as other forms of asthma, including:

There are a few symptoms that may also be present that are not typically associated with asthma including:

While eosinophilic asthma is an immune response related to allergies, many people diagnosed with it do not suffer from allergies to mold, mildew, or other common allergens.


Eosinophilic asthma is under-diagnosed. It is not considered common even though the prevalence is thought to be higher than previously believed.

If eosinophilic asthma is the cause of your asthma and is not diagnosed, you may struggle to get your severe asthma under control.

You generally want to be seen by a pulmonologist if you are concerned. Allergists and immunologists may also be helpful in your thorough evaluation.

Eosinophil Cell Count

Performing a cell count of eosinophils from an induced sputum sample is considered the gold standard measure of inflammatory cell counts, but it is difficult to obtain, time-consuming, and observer-dependent. It often requires the use of a specific lab staffed with experts.

When collecting the specimen, you want to ensure that you are not spitting saliva, but coughing up sputum from your airways. The coughed up specimen can then be analyzed in a lab to see if the sputum eosinophil count is equal to or great than 3%.

To help induce sputum, your healthcare provider or a respiratory therapist may give you a dose of salbutamol or another fast-acting bronchodilator. This treatment is then followed by giving you a nebulized hypertonic saline. The higher concentration of saline when inhaled irritates the airways and helps to induce coughing.

Airway Biopsy

Another way to determine whether you have e-asthma is with an airway biopsy, which is performed during a bronchoscopy. This procedure can be used to identify abnormal cells in the diagnosis of several different lung diseases.

However, this method is not recommended as the first step in identifying eosinophilic asthma unless a sufficient sputum sample can't be obtained since it is an invasive procedure that requires some sedation and can have complications.

Other Methods

Other methods have been developed to help diagnose e-asthma. Your healthcare provider may check a complete blood count (CBC) to check for eosinophilia (increased eosinophil count).

A careful interpretation of your blood eosinophils will be considered by your healthcare provider since elevated counts in your blood do not guarantee that you have eosinophilic asthma. That said, it may help your healthcare provider in further differentiating any other symptoms you are having.

Other diagnoses that may be considered if you have an elevated eosinophil count in your blood include parasitic infection, hypereosinophilic syndrome, autoimmune disorders, adrenal insufficiency, some cancers, and medication reactions.

Other tests may be used to help diagnose asthma. One of these is the fractional exhaled nitric oxide (FeNO) breathing test,which measures the amount of nitric oxide in your breath when you exhale. High levels are a possible indication of lung inflammation that may be a response to an allergen.

Many factors can affect the results of a FeNO test, including the use of steroids, age, sex, atopy (tendency to develop allergies), and smoking status.Although FeNO can play a useful role in determining if someone has asthma, it should not be relied on alone—either to diagnose the condition or to predict how it might progress, according to updated recommendations for asthma management issued in December 2020.

Sometimes a blood test is performed as part of an asthma workup to measure levels of periostin, a biomarker in the epithelial cells of the airways. Periostin levels tend to be elevated in response to asthma that activates certain immune cells (TH2).

However, while in some studies periostin testing has been shown to be an excellent substitute for testing sputum, in others results have been variable. Induced sputum and blood eosinophil counts are still preferable to FeNO and periostin according to most clinicians and guidelines.

Periostin is a biomarker in your airway epithelial cells. Periostin levels tend to be elevated in asthma that activates certain immune cells (TH2) and in some studies has been shown to be an excellent surrogate for testing sputum.

But results are variable in other studies and the test is not easily available. Induced sputum and blood eosinophil counts are still preferable to FeNO and periostin according to most clinicians and guidelines.


First-line treatment of eosinophilic asthma should include your standard asthma treatment regimen. Often you will experience good results from inhaled corticosteroids (ICS) that are used as part of the standard asthma treatment guidelines.

If your healthcare provider has diagnosed you with eosinophilic asthma, they may alter the standard approach used with inhaled corticosteroids. Corticosteroid medications include:

  • QVAR Redihaler (beclomethasone diproprionate HFA)
  • Pulmicort Flexhaler (budesonide)
  • Flovent HFA (fluticasone proprionate)
  • Asmanex HFA (mometasone)

While inhaled corticosteroids often have beneficial effects, some people have steroid-refractory eosinophilic asthma, which simply means that your asthma does not have symptomatic or clinical benefit from taking inhaled corticosteroids.

If you have tried one or more inhaled corticosteroids without benefit, your physician will likely step up your asthma care to include additional treatment options like long-acting bronchodilators (included in combination inhalers like Advair HFA and Symbicort) and/or leukotriene modifiers like Singulair (montelukast). If standard step-up therapies are insufficient for controlling your asthma, you may discuss some of the more recently discovered medications used to target eosinophils in eosinophilic asthma specifically.

There are five targeted therapies that have received approval from the U.S. Food and Drug Administration (FDA) for the treatment of allergic asthma:

  • Nucala (mepolizumab), formerly known as Bosatria, is a monoclonal antibody again interleukin-5 (IL-5)
  • Cinqair (reslizumab), another monoclonal antibody against the IL-5 receptor
  • Xolair (omalizumab): indicated to treat moderate-to-severe persistent asthma in patients 6 years old or older
  • Fasenra (benralizumab), another monoclonal antibody against the IL-5 receptor
  • Dupixent (dupilumab), indicated to treat moderate-to-severe eosinophilic asthma in patients 12 years old or older.

The five medications listed above have shown favorable results if you are still symptomatic despite good adherence to your prescribed corticosteroid regimen. Of these, omalizumab tends to be the least successful, as it affects allergies more specifically than mepolizumab and reslizumab.

These medications are also generally well tolerated with minimal side-effects with the likelihood that you will also be able to decrease your use of corticosteroids. Minimizing use of steroids also brings a reduction in side effects that can increase your quality of life.


Follow-up is recommended as targeted therapies are not a cure, but a treatment. Be prepared for periodic testing and to discuss the following with your healthcare provider at follow-up appointments:

  • Pulmonary function testing
  • Symptoms experienced since last visit (improved or worsening)
  • The frequency of asthma exacerbations
  • Resolution of complications like loss of smell
  • Overall health status
  • Tracking of Quality of Life surveys
  • Laboratory analysis

A standard follow-up appointment is about two to six weeks after starting a new medication. If you have experienced positive results, you will continue on the medication prescribed and follow up in one to six months. Even if you are not on one of the newer asthma medications targeting eosinophils, most should see a physician approximately once every three months for evaluation and management of chronic persistent asthma.

A Word From Verywell

While eosinophilic asthma is often associated with severe asthma, treatment is possible if diagnosed properly. Untreated eosinophilic asthma will likely result in difficulty controlling asthma exacerbations—which not only worsens your quality of life but can be life-threatening. Working with your pulmonologist or allergist/immunologist with targeted therapies can help you get back the quality of life that you deserve and may reduce the frequency of your asthma exacerbations.

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Additional Reading

By Kristin Hayes, RN
Kristin Hayes, RN, is a registered nurse specializing in ear, nose, and throat disorders for both adults and children.