Eosinophilia is a higher than normal number of a type of white blood cell called eosinophils. These cells help protect the body from certain types of infections. They are also involved in allergic reactions.

White Blood Cells
White Blood Cells
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Causes may be:

  • Problems in genes that control cell growth
  • A change in the number of cells due to certain cancers
  • Health problems, such as infections, problems with the immune system, or allergies

Risk Factors

This symptom is more common in people who have other family members who have it.

Other things that may raise the risk are:

  • Allergies, including food allergies
  • Infections, mainly those caused by parasites
  • Inflammatory conditions in the body
  • Skin problems
  • Certain blood cancers
  • Reactions to medicines
  • Conditions or toxic exposures from work



Some people may not have symptoms. The symptoms a person will have depend on what is causing the eosinophilia. For example:

  • Asthma:
    • Wheezing
    • Breathing problems
  • Infections from a parasite:
    • Belly pain
    • Diarrhea
    • Fever
    • Cough
    • Rashes


The doctor will ask about your symptoms and health history. A physical may be done.

Initial tests may be:

  • Blood tests
  • Stool tests
  • Biopsy
  • Bone marrow tests

Other tests that may be done depend on the problems you are having. This may involve:

  • X-rays
  • CT scan
  • MRI scan
  • Endoscopy



The focus of care depends on the problems a person has. Corticosteroids may be given to ease inflammation. This will also lower the number of eosinophils.


There are no known guidelines to prevent this symptom.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.


American Academy of Allergy, Asthma, and Immunology https://www.aaaai.org 

American Society of Hematology http://www.hematology.org 


Allergy Asthma Information Association http://aaia.ca 

Health Canada https://www.canada.ca 


Eosinophilia. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/hematology-and-oncology/eosinophilic-disorders/eosinophilia. Accessed October 23, 2020.

Eosinophilia. Patient website. Available at: https://patient.info/doctor/eosinophilia. Accessed October 23, 2020.

Eosinophilia—approach to the patient. EBSCO DynaMed website. Available at: https://www.dynamed.com/approach-to/eosinophilia-approach-to-the-patient. Accessed October 23, 2020.

World Health Organization (WHO) 2017 update on diagnosis, risk stratification, and management of WHO-defined eosinophilic disorders can be found in Am J Hematol 2017 Nov;92(11):1243.