An eosinophil count is the number of eosinophils in the body. Eosinophils, a type of white blood cell, help fight off bacterial and viral infections. A person may require an eosinophil count blood test if they show signs of certain infections or allergic reactions

For adults, a normal eosinophil count is up to in the blood.

Doctors may also measure eosinophils in cells per microliter (cells/mcL). The number will be the same in both cells/mm3 and cells/mcL.

A doctor may recommend the eosinophil test if a person has abnormal results from another blood test.

A person may have abnormal eosinophil blood test results if they show symptoms of:

  • Cushing's syndrome, which is a hormone disorder
  • acute hypereosinophilic syndrome, which causes organ damage

In this article, we cover what people can expect from their eosinophil count test, as well as what the test results may mean.

Abnormal results indicate that the eosinophil count is too high or too low. Below, we break down what these results might mean.

High eosinophil count

A high eosinophil count may indicate an autoimmune disease.

Having a higher-than-normal eosinophil count in the bloodstream is called eosinophilia.

This condition may be:

Mild eosinophilia does not often cause symptoms, but moderate or severe cases can result in damage to organs in the body.

People may have a high eosinophil count if they have:

  • certain cancers, such as leukemia
  • a parasitic infection
  • asthma
  • allergies
  • eczema
  • hypereosinophilic syndrome, a disorder characterized by high eosinophil levels without a parasitic, allergic, or other cause of eosinophilia
  • autoimmune disease

Low eosinophil count

Lower numbers of eosinophils in the blood can suggest:

  • Alcohol misuse: Alcohol misuse can cause the levels of eosinophils and other white blood cells to drop, which the body's immune system response to infections and other disease states.
  • Overproduction of cortisol: Excess levels of cortisol, which is a glucocorticosteroid hormone, may have links to a lower eosinophil count and lower immune function. People with Cushing's syndrome overproduce cortisol.

If a person has a lower-than-normal eosinophil count but no cortisol production issues or excessive alcohol exposure, a doctor may look at other different white blood cell counts.

It is not usually a cause for concern if these are normal. If other white blood cell counts are abnormal, however, further testing may be necessary to determine the underlying cause.