Eosinophils and Eosinophil Count Test

What Are Eosinophils?

Eosinophils are a kind of white blood cell that helps fight disease. The exact role of eosinophils in your body isn't clear, but they're usually linked with allergic diseases and certain infections. They're made in your bone marrow and then travel to different tissues.

Eosinophils do two important things in your immune system: curb infections and boost inflammation, which can help you fight off a disease.

What Is Eosinophilia?

Eosinophilia is when you have a higher than normal number of these special cells in your blood or tissue.

What Is an Eosinophil Count?

If you take a blood test and the results aren’t in the normal range, your doctor may recommend more tests to figure out the problem. If this happens on a test called a white blood cell differential, you may need to get another blood test called an absolute eosinophil count. You might also get this test if your doctor thinks you have a particular kind of disease.

What Does a High Eosinophil Count Mean?

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

• Acute hypereosinophilic syndrome, a rare condition that’s similar to leukemia and can be life-threatening
• An allergic disorder like asthma or hay fever
• Autoimmune conditions
• An infection caused by a parasite or fungus
• A reaction to certain medications
• Asthma
• 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
• Eczema (itchy, inflamed skin)
• Leukemia and other blood disorders

What Does a Low Eosinophil Count Mean?

A lower than normal eosinophil count could be because:

• You’ve had too much alcohol
• Your body is making too much of certain steroids, like cortisol

What the Test Does

The eosinophil count measures the amount of eosinophils in your blood.

The key is for eosinophils to do their job and then go away. But if you have too many eosinophils in your body for a long time, doctors call this eosinophilia. It can cause chronic inflammation, which could damage tissues.

Conditions where too many eosinophils are in the body include eosinophilic esophagitis (a disorder in your esophagus) and eosinophilic colitis (in your large intestine). Eosinophilic disorders also can happen in your stomach, small intestine, blood, or other organs. Sometimes, a biopsy will show that you have a high amount of eosinophils in your tissues, but you might not have a high amount in your blood.

How the Test Is Done

If your doctor wants an absolute eosinophil count, you’ll need a blood test. During the test, a health care worker will put a needle into one of your veins and take out some blood.

In a lab, a technician will add a special stain to your blood sample. This let them see the eosinophils and count how many you have in every 100 cells. They’ll multiply that percentage by your white blood cell count to get your absolute eosinophil count.

What Do the Results Mean?

Eosinophils make up 0.0 to 6.0 percent of your blood. The absolute count is the percentage of eosinophils multiplied by your white blood cell count. The count may range a bit between different laboratories, but a normal range is usually between 30 and 350.

A count of more than 500 cells per microliter of blood is considered eosinophilia.

Next Steps

The eosinophil count can help confirm a diagnosis. Once the doctor knows what’s causing the eosinophilia, they can treat the condition that’s behind it. You’ll probably get some other tests to help make a diagnosis.

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