Posted September 13, 2022 by Anusha ‐ 4 min read

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.

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 blood

  • Eczema (itchy, inflamed skin)

  • Leukemia and other blood disorders

What is eosinophilia?

  • Eosinophilia is an unusually high number of eosinophils in your blood (≥ [greater than or equal to] 500 eosinophils per microliter).

  • Eosinophils are one of several white blood cells that support your immune system.

  • They’re part of your body’s defense system against allergens and help protect your body from fungal and parasitic infections.

  • Certain medical conditions and medications can cause high eosinophil counts.

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 causes eosinophilia?

  • Many conditions cause your eosinophil counts to increase in your blood.

  • Some conditions, like seasonal allergies, asthma and reactions to medications are very common, and often aren’t very serious. Infections, especially from parasites, can also lead to eosinophilia.

  • Problems with immune regulation can also cause eosinophilia, including autoimmune diseases like inflammatory bowel disease, autoimmune myocarditis, vasculitis and sarcoidosis.

  • Blood cancers that make these cells inappropriately can also cause eosinophilia.

  • Finally, genetic changes that are hereditary (passed on by your biological parents) can cause eosinophilia.

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.

How do healthcare providers diagnose eosinophilia?

  • Healthcare providers typically discover eosinophilia during a routine blood test called a complete blood count (CBC) with a differential white blood cell count.

  • Depending on your situation, your healthcare provider may do more tests to find out why your eosinophil levels are higher than normal.

How do healthcare providers treat eosinophilia?

  • Healthcare providers treat the underlying condition or issue that’s causing high eosinophil counts.

  • For example, if you have eosinophilic esophagitis, your healthcare provider may prescribe steroids or other medications.

  • If you have high eosinophil levels because you have allergies or chronic sinusitis, your healthcare provider may recommend allergy testing to find out what causes the allergic reaction that triggered eosinophilia.

  • If a medication is causing eosinophilia, your healthcare provider will usually recommend stopping or avoiding it.

  • If there’s an infection, your healthcare provider will treat it.

  • If there’s a blood cancer, your healthcare provider will treat it.

diseases disorders eosinophils

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