Eosinophil count
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Eosinophil countFull blood count

Eosinophil count

May 3, 2022

Eosinophil count

What is an eosinophil count?

White blood cells are an important part of your body’s immune system. They’re vital to protecting you from invading bacteria, viruses, and parasites. Your bone marrow produces all five of the different kinds of white blood cells in the body.

Each white blood cell lives anywhere from several hours to several days in the bloodstream. An eosinophil is a type of white blood cell. Eosinophils are stored in tissues throughout the body, surviving for up to several weeks. The bone marrow continually replenishes the body’s white blood cell supply.

The number and type of each white blood cell in your body can give doctors a better understanding of your health. Elevated levels of white blood cells in your blood can be an indicator that you have an illness or infection. Elevated levels often mean your body is sending more and more white blood cells to fight off infections.

An eosinophil count is a blood test that measures the number of eosinophils in your body. Abnormal eosinophil levels are often discovered as part of a routine complete blood count (CBC) test.

Why is this analysis important?

A white blood count differential test (including an eosinophil count) is often done alongside a complete blood count (CBC) and determines the percentage of each kind of white blood cell present in your blood. This test will show if you have an abnormally high or low count of white blood cells. White blood cell counts can vary in certain diseases.

What are some of the causes of a high eosinophil count?

Eosinophilia is classified as either mild, moderate, or severe depending on your level compared to the range defined by the laboratory. This can be due to any of the following:

  • Infection by parasitic worms

  • Autoimmune disease

  • Severe allergic reactions

  • Eczema

  • Asthma

  • Seasonal allergies

  • Ulcerative colitis

  • Scarlet fever

  • Lupus

  • Crohn’s disease

  • A significant drug reaction

  • An organ transplant rejection

  • Leukemia and certain other cancers

What are some of the causes of a low eosinophil count?

An abnormally low eosinophil count can be the result of:

  • Intoxication from alcohol or

  • Excessive production of cortisol, like in Cushing’s disease. Cortisol is a hormone naturally produced by the body.

  • Low eosinophil counts may also be due to the time of day. Under normal conditions, eosinophil counts are lowest in the morning and highest in the evening.

Unless alcohol abuse or Cushing’s disease is suspected, low levels of eosinophils are not usually of concern unless other white cell counts are also abnormally low. If all white cell counts are low, this can signal a problem with the bone marrow.

Other considerations

Ongoing research continues to uncover an expanding list of roles performed by eosinophils. Two important functions are within your immune system. Eosinophils destroy invading germs like viruses, bacteria, or parasites such as hookworms. They also have a role in the inflammatory response, especially if an allergy is involved.