Eosinophilic Asthma and Sputum Eosinophilia

Medically Reviewed by Dan Brennan, MD on February 03, 2022

Eosinophilic asthma is an uncommon type of asthma that’s often severe. It’s named after immune cells called eosinophils, which can go into overdrive and make it harder for you to breathe. The best place to check if eosinophil levels are too high is in what you cough up from you lungs. That gunk is called sputum.

What Are Eosinophils?

They’re special white blood cells, which help your immune system fight off infections and other foreign invaders. One way they do this is by controlling inflammation. Chemicals from the white blood cells converge on the site of the injury to help it heal, which temporarily swells and reddens the area.

But too much inflammation can damage healthy tissue. When eosinophils get too active or there are too many of them, these cells can lead to allergies, asthma, and other diseases.

Eosinophils and other blood cells originate in your bone marrow. They then move into the bloodstream and eventually land in tissues, including your lungs. Once there, the eosinophils can stay in the organ for a couple of weeks.

What Is Sputum Eosinophilia?

When you have too many eosinophils in your blood or tissues, it’s a condition called eosinophilia. If you have eosinophilic asthma, you have too many of these immune cells in your blood and, more worrisome, in your lungs.

Those harmful extra immune cells in your lungs will turn up in your sputum. If your doctor says you have sputum eosinophilia, that’s what they mean. Those surplus eosinophils may be hard to chase away, even with treatment.

Keeping Tabs on Sputum Counts

Knowing that your asthma is linked to sputum eosinophilia can help you understand your condition. Your doctor can keep tabs on your sputum cells to help decide on the best ways to treat your asthma.

Normally, eosinophils should make up no more than 2%-3% of all the types of cells in your sputum. If the levels are higher than that, you have eosinophilic asthma.

The number of eosinophils in your lungs and sputum will rise and fall, depending on the condition of your asthma. And studies show that your eosinophilic levels often closely track how severe your asthma symptoms are. The number of those cells also may be a clue for how well your treatment is working.

Ask your doctor if they recommend tracking your sputum counts regularly. It’s one way to help keep your asthma under control.

Show Sources


ERJ Open Research: “Management of the patient with eosinophilic asthma: a new era begins.”

Journal of Allergies and Asthma: “Diagnosis and management of eosinophilic asthma: a U.S. perspective.”

Apfed: American Partnership for Eosinophilic Disorders: “Eosinophilic Asthma.”

Mayo Clinic: “Eosinophilia.”

Cincinnati Children’s: “What is an eosinophil?”

Cleveland Clinic: “Eosinophilia.”

The Journal of Allergy and Clinical Immunology: In Practice: “Asthma Control and Sputum Eosinophils: A Longitudinal Study in Daily Practice.”

CHEST Journal: “Point: Is Measuring Sputum Eosinophils Useful in the Management of Severe Asthma? Yes.”

© 2022 WebMD, LLC. All rights reserved. View privacy policy and trust info