Eosinophils are a type of white blood cell. These white blood cells help to protect the body from certain types of infections and are involved in allergic responses. Eosinophils are created in the bone and move through the body in the blood.

Eosinophilia is an abnormally high number of these white blood cells. There may be high levels of eosinophils in the blood, in the tissue, or both.

There are several types of eosinophilia including:

  • Familial eosinophilia—caused by problems in genes that control eosinophil growth
  • Secondary eosinophilia—related to a parasitic infection, autoimmune reaction, allergic, or other inflammatory illnesses
  • Primary eosinophilia—change in production of eosinophils associated with certain leukemias or chronic myeloid disorders such as myelodysplastic syndrome

White Blood Cells
White Blood Cells
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Eosinophilia may be caused by an illness to a specific area or an overproduction of these cells. The cause will vary based on type of eosinophilia. Causes include:

  • Allergy diseases, such as asthma, eczema, and allergic rhinitis
  • Diseases from parasitic worms

Sometimes the cause of eosinophilia is not known.