What Is an Eosinophil Count?

If a blood test comes back with a result that’s outside the normal range, your doctor may recommend follow-up tests to figure out the problem. If this happens on a test called a white blood cell differential, he may want to do another blood test called an absolute eosinophil count. He also may want to do that test if he thinks you may have a particular kind of disease.

An eosinophil count can help make a diagnosis for a few conditions. You might have a high count with the following:

  • Eczema (inflammation of your skin)
  • Allergic disorders like asthma or hay fever
  • An infection caused by a parasite
  • A reaction to certain medications
  • The early stages of Cushing’s disease, a rare condition that can happen if you have too much of a hormone called cortisol in your blood
  • Acute hypereosinophilic syndrome, another rare condition that’s similar to leukemia and can be life-threatening


What the Test Does

The eosinophil count measures the amount of eosinophils in your blood. They’re a kind of white blood cell that helps fight disease. They’re made in your bone marrow and then travel to different tissues. They do two important things in your immune system: fight off infections and boost inflammation, which can help you fight off a disease.

If you have too many eosinophils in your body for a long time, it’s called eosinophilia, and it can cause chronic inflammation. This can damage tissue and lead to things like eosinophilic esophagitis (a disorder in your esophagus) or eosinophilic colitis (in your large intestine). Eosinophilic disorders also can happen in your stomach, small intestine, blood, or other organs.

Generally, a normal test value is less than 500 cells per microliter (cells/mcL). This number can be different at different laboratories, so it’s important to talk with your doctor about your results.

How the Test Is Done

If your doctor wants an absolute eosinophil count, you’ll need a blood test. During the test, a needle will be put into your vein and blood will be taken out.

The sample is sent to a lab, where a technician will add a special stain to your blood so they can see the eosinophils. Then they’ll count how many you have in every 100 cells. That number is multiplied by your white blood cell count to get your absolute eosinophil count.

WebMD Medical Reference Reviewed by Neha Pathak, MD on October 06, 2017



UCSF Medical Center: "Eosinophil Count Absolute."

UCLA: "Cushing's Disease."

Mayo Clinic: "Eosinophilia."

Cincinnati Children’s Hospital: "What is an Eosinophilic Disorder?"

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