Eosinophils are a type of white blood cell. They help protect the body from certain types of infections. They’re also involved in allergic reactions. Eosinophils are made in the bone. They move through the body in the blood.

Eosinophilia is a high number of this cell type. High levels may be found anywhere in the body.

There are 3 types:

  • Familial—caused by problems in genes that control eosinophil growth
  • Primary—change in the number of eosinophils made because of certain blood cancers
  • Secondary—from infections, immune system problems, or allergies

White Blood Cells
White Blood Cells
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Causes of eosinophilia:

  • Illness in a certain area
  • The body makes too many of these cells

The cause differs based on the type:

  • Conditions caused by allergies or inflammation
  • Conditions caused by infections

Sometimes the cause is unknown.

Risk Factors

People in your family with the same problems make your chances of the familial type higher.

Your chances of the other types are higher if you have:

  • Allergies—including food
  • Infections—mainly caused by parasites
  • Inflammatory conditions
  • Skin conditions
  • Certain blood cancers
  • Reactions to medicines
  • Conditions or toxic exposures from work



Some people may not have symptoms. In those that have them, they depend on the underlying cause:

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

Rarely, these may happen:

  • Weight loss
  • Night sweats
  • Swollen glands in the neck, groin, or other parts of the body
  • Skin rashes
  • Numbness and tingling due to nerve damage


The doctor will ask about your symptoms and health history. You may have:

  • A physical exam
  • Blood tests
  • Biopsy
  • Stool tests
  • Bone marrow tests

Tests depend on the problems you have. They may focus on where problems are such as the heart or lungs. This may involve:

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



The focus of care depends on the problems you’re having. If the cause is unknown, care may involve medicines. Corticosteroids will ease inflammation. They will also lower the number of eosinophils. These medicines come in different forms.


If you are at high risk for eosinophilia, your doctor will watch you for any changes.

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. Updated November 2016. Accessed July 13, 2018.

Eosinophilia. Patient website. Available at: https://patient.info/doctor/eosinophilia. Updated March 12, 2014. Accessed July 13, 2018.

Eosinophilia—approach to the patient. EBSCO DynaMed Plus website. Available at:  http://www.dynamed.com/topics/dmp~AN~T917758/Eosinophilia-approach-to-the-patient  . Updated June 5, 2017. Accessed July 13, 2018.

Tefferi A. Blood eosinophilia: a new paradigm in disease classification, diagnosis, and treatment.. Mayo Clin Proc. 2005;80(1):75-83.