Find a Doctor Find a Doctor
Time to see a specialist? Time to see a specialist?
We found [COUNT] Specialists
who treat [INTEREST]
We found [COUNT] Specialists
who treat [INTEREST]
[TELEHEALTH] offer Telehealth options.
Controlling Severe Asthma

This content is created by Healthgrades and brought to you by an advertising sponsor. More

This content is created or selected by the Healthgrades editorial team and is funded by an advertising sponsor. The content is subject to the Healthgrades medical review process for accuracy, balance and objectivity. The content is not edited or otherwise influenced by the advertisers appearing on this page except with the possible suggestion of the broad topic area. For more information, read the Healthgrades advertising policy.

Eosinophils: How These Little Cells Make Asthma Worse

While we’re not sure of the exact cause of asthma, we do know that tiny cells called eosinophils may play a role, especially in patients with severe asthma.

eosinophils illustration

Asthma is a chronic lung disease, which is characterized by airway inflammation and spasming (tightening). An eosinophil is one of the five types of white blood cells circulating in our blood. Eosinophils function as part of the body’s immune system. They play a major role in fighting infections, such as viral and parasitic infections, releasing chemicals toxic to these invaders. In doing this, eosinophils create inflammation.

However, inflammation has a damaging effect when it comes to the lungs’ airways. Eosinophilia (i.e., high eosinophil numbers) can be associated with chronic sinusitis, chronic obstructive pulmonary disease (COPD), allergies, and of course, asthma. In fact, eosinophilia is associated with more severe asthma and more frequent asthma attacks.

Eosinophils and Asthma

These high levels of eosinophils have been found not only in the blood of asthmatics, but lining the airways themselves, and in sputum (phlegm). When activated, these eosinophils release chemicals which are harmful to the lungs. These chemicals damage the airways, immediately causing mucous production and spasm. Over the long term, the effect of these chemicals causes chronic inflammation and remodeling (scarring) of the airways. 

Remodeling is irreversible, non-repairable, and results in airway narrowing, which makes asthma much more difficult to treat. The effects of eosinophils on the airways result in asthma symptoms such as coughing, wheezing, chest tightness and shortness of breath.

Asthma isn’t always made worse by eosinophils, but patients with eosinophilic asthma have more emergency room visits and hospitalizations for asthma. They experience frequent exacerbations (flare-ups), frequent use of oral steroids, and poor asthma control despite taking many medications at high doses.

Treating Eosinophilic Asthma

Historically, therapies for asthma aim to reduce inflammation and relax airway muscles to reduce symptoms. Medications include inhaled steroids, leukotriene inhibitors and bronchodilators. However, patients with severe asthma have not always achieved sufficient asthma control with these treatments.

New biologic treatments are now targeting the eosinophil directly. Biologics are medications produced from living organisms that block targets to reduce inflammation. Lowering eosinophil levels in the blood and sputum of asthmatics results in fewer asthma attacks and doctor’s appointments for asthma.

Mepolizumab (Nucala) was the first biologic approved to reduce the number of eosinophils in patients with eosinophilic asthma. Other biologics for asthma include Cinqair, Dupixent, Fasenra and Xolair.

Ask your doctor whether a medication that targets eosinophils directly could help you improve your asthma control.

Was this helpful?
  1. Arron JR, Choy DF, Scheerens H, Matthews JG. Noninvasive biomarkers that predict treatment benefit from biologic therapies in asthma. Ann Am Thorac Soc. 2013;10(Suppl):S206–213.
  2. Carr TF, Berdnikovs S, Simon HU, Bochner  BS , Rosenwasser LJ. Eosinophilic bioactivities in severe asthma. World Allergy Organization Journal. 2016; 9:21.
  3. Green RH, Brightling CE, McKenna S, et al. Asthma exacerbations and sputum eosinophil counts: a randomised controlled trial. Lancet. 2002;360(9347):1715–21.
  4. Moore WC, Fitzpatrick AM, Li X, et al. Clinical heterogeneity in the severe asthma research program. Ann Am Thorac Soc. 2013;10(Suppl):S118–124.
  5. Moore WC, Hastie AT, Li X, et al. Sputum neutrophil counts are associated with more severe asthma phenotypes using cluster analysis. J Allergy Clin Immunol. 2014;133(6):1557–63. e1555.
  6. Pavord ID, Korn S, Howarth P, et al. Mepolizumab for severe eosinophilic asthma (DREAM): a multicentre, double-blind, placebo-controlled trial. Lancet. 2012;380(9842):651–9.
  7. Tran TN, Khatry DB, Ke X, Ward CK, Gossage D. High blood eosinophil count is associated with more frequent asthma attacks in asthma patients. Ann Allergy Asthma. Immunol. 2014;113(1):19–24.
  8. Wenzel S. Severe asthma in adults. Am J Respir Crit Care Med. 2005;172:149-160.
  9. Wenzel SE, Schwartz LB, Langmack EL, et al. Evidence that severe asthma can be divided pathologically into two inflammatory subtypes with distinct physiologic and clinical characteristics. Am J Respir Crit Care Med. 1999;160(3):1001–8.
  10. Zeiger RS, Schatz M, Li Q, et al. High blood eosinophil count is a risk factor for future asthma exacerbations in adult persistent asthma. J Allergy Clin Immunol Pract. 2014;2(6):741–50.
  11. Zhang JY, Wenzel SE. Tissue and BAL based biomarkers in asthma. Immunol Allergy Clin North Am. 2007;27(4):623–32.

Medical Reviewer: William C. Lloyd III, MD, FACS
View All Controlling Severe Asthma Articles
THIS CONTENT DOES NOT PROVIDE MEDICAL ADVICE. This content is provided for informational purposes and reflects the opinions of the author. It is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional regarding your health. If you think you may have a medical emergency, contact your doctor immediately or call 911.