Eosinophils are a type of white blood cell that protect your body from parasites, allergens, foreign bacteria and outside organisms. Eosinophils are larger than most cells and make up less than 5% of all white blood cells in your body.


What are eosinophils?

Eosinophils are a type of white blood cell (leukocytes). There are three types of white blood cells, all with various functions to help your immune system, including granulocytes, lymphocytes and monocytes. Eosinophils are one of three types of granulocytes, along with neutrophils and basophils. Eosinophils prevent foreign organisms from growing inside of host cells (parasites).


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What do eosinophils do?

When an unfamiliar organism or particle enters your body, your white blood cells divide into special troops to locate and destroy the invader before it causes harm to other cells. Each type of white blood cell undergoes specialized training before leaving your bone marrow and traveling to your tissues where they watch for invaders to enter your body so they can destroy them. Eosinophil cells contain small sand-like granules that release a toxic protein to destroy and consume invading organisms. Eosinophils help your body defend itself from:

  • Infections by parasites (strongyloidiasis, pinworms).
  • Organisms that grow on other cells (intracellular bacteria).
  • Exposure to allergens (immediate hypersensitivity reactions).


Where are eosinophils located?

Eosinophils are a type of white blood cell that lives in your body’s tissues. The most common place to find eosinophils include:


What do eosinophils look like?

Eosinophils are microscopic cells that are spherical. The cells are clear in your body but under a microscope, an acidic dye changes the cell’s color to be examined. The dye changes the cell to a purple or pink color.

Eosinophils are larger than other cells and stand out because of their two-lobed nucleus, which looks like two separate raindrops connected by a thread. The nucleus contains the cell’s DNA and floats in a protein that appears sandy in texture (granules).

How many eosinophils are in my body?

Eosinophils are a type of white blood cell. White blood cells make up 1% of the cells in your body. There are less than 5% of eosinophils circulating among white blood cells in healthy adults.


Where are eosinophils made?

Eosinophils form in the soft tissue of your bones (bone marrow). After maturing in your bone marrow, eosinophils travel to fatty tissue in your body, like your stomach.

Conditions and Disorders

What are common conditions that affect eosinophils?

Conditions that affect eosinophils are rare. There are two types of eosinophil conditions for both low and high cell counts.

Eosinopenia is the result of having a less than normal amount of eosinophils in your body. Types of eosinopenia include:

  • Cushing’s syndrome: This condition occurs when there is too much cortisol in your body and not enough eosinophil cells. Cortisol is a hormone that regulates your blood sugar and turns food into energy.
  • Sepsis: Sepsis is a severe medical condition that causes widespread swelling (inflammation) and blood clotting. It is most often the result of a bacterial, fungal, parasitic or viral infections.

Often, if you have an occasional low number of eosinophil cells, it doesn’t pose a major threat to your health because other cells in your immune system compensate for the lack of eosinophils. Long-term eosinopenia is dangerous and requires immediate treatment from your healthcare provider.

Eosinophilia occurs when you have more eosinophils in your blood than normal. Your healthcare provider will diagnose a high eosinophil count based on where eosinophils are living:

  • Eosinophilic gastrointestinal disorders (EGID) are conditions that affect the gastrointestinal tract and cause a cluster of eosinophil cells to inflame the area and create swelling. This is the most common condition affecting eosinophils. EGIDs affect the large intestine (eosinophilic colitis), esophagus (eosinophilic esophagitis), stomach (eosinophilic gastritis) and both the stomach and small intestine (eosinophilic gastroenteritis) and bladder (eosinophilic cystitis).
  • Eosinophilic lung disorders, including eosinophilic asthma, bronchitis and pneumonia, affect your lungs like a severe form of asthma, bronchitis and pneumonia, where your lungs are clogged with inflamed cells. Eosinophilic lung disorders make breathing difficult.
  • Eosinophilic blood and tissue disorders affect the connective tissue beneath your skin (eosinophilic fasciitis), skin (eosinophilic pustular folliculitis) and cells in your blood, blood vessels and vital organs like your heart and kidneys (eosinophilic granulomatosis with polyangiitis, formerly Churg-Strauss syndrome). Eosinophilic blood and tissue disorders are the result of having too many eosinophils, which take over blood vessels, making it difficult for blood to flow through your body without treatment.

What are common symptoms of eosinophil conditions?

Symptoms of eosinophil conditions often appear near the location of the disorder. General symptoms of eosinophil conditions include:

What causes eosinophil conditions?

There are several factors that affect the number of eosinophils in your blood including:

Is eosinophilia the result of a contagious infection?

A high eosinophil count can be the result of a contagious infection, but it is not always the primary cause of eosinophilia. Parasites cause eosinophil cells to increase and parasites spread from human-to-human contact or animal-to-human contact, especially from dogs and cats. Your healthcare provider will test for a parasitic infection to confirm the diagnosis and offer treatment options, which will reduce your eosinophil count to a normal level.

What are common tests to check the health of your eosinophils?

Diagnosing eosinophil conditions starts with a complete blood count test where your healthcare provider will examine a sample of your blood to count the cells in your body, specifically your white blood cells, to make sure those aren’t too high or too low. Other tests to check the health of your eosinophil cells include:

  • Absolute eosinophil count: A blood test, similar to the complete blood count, specifically identifies how many eosinophils are in a sample of your blood. After your healthcare provider removes a sample of your blood from your vein, they will examine that sample under a microscope. They will add dye to the sample to make your cells more visible, then count how many eosinophils are present in the sample out of 100 cells. That percentage is multiplied by your white blood cell count to give an absolute eosinophil count.
  • Bone marrow biopsy: Your healthcare provider will use a needle to remove a sample of your bone marrow to examine the quantity and quality of the cells in your body and where they originate.

To target the location of the eosinophil condition, your healthcare provider may perform localized tests including:

What is a normal eosinophil count?

A normal eosinophil count is between 30 and 350 cells per microliter of blood. A count is higher than normal with results of more than 500 cells per microliter of blood and low if it is less than 30 cells per microliter of blood.

Often, a one-time, low eosinophil count will not be a threat to your overall health, even if your count is zero. Your white blood cells in your immune system will compensate and produce more cells to make up for the lack of eosinophil cells in your body.

What is a high eosinophil count?

Your healthcare provider will classify a high count of eosinophils (eosinophilia) by severity based on the results of an absolute eosinophil count:

  • Mild: Cell count between 500 and 1,500 eosinophils per microliter of blood.
  • Moderate: Cell count between 1,500 and 5,000 eosinophils per microliter of blood.
  • Severe: Cell count greater than 5,000 eosinophils per microliter of blood.

Does a high eosinophil count indicate cancer?

Although rare, having a consistently high eosinophil count can be an indication of cancer in your body. A high eosinophil count could relate to several cancers including:

If your healthcare provider suspects cancer, they will perform further tests to diagnose and treat the condition, like a biopsy, additional blood tests or imaging tests.

What are common treatments for a high eosinophil count?

Treatment for conditions with a high eosinophil count varies depending on the location and severity of the diagnosis. Treatment to reduce a high eosinophil count includes:

  • Avoiding certain types of foods for esophagitis including fatty, spicy and acidic foods.
  • Stopping or changing the dose of a medication if you had a drug reaction.
  • Taking anti-inflammatory medications.

Most high eosinophil count conditions are chronic and require long-term treatment and management.

What are common treatments for a low eosinophil count?

Treatment for conditions with a low eosinophil count includes:

Your body will often detect a low number of eosinophils on its own and other members of your immune system will step up to compensate for the lack of eosinophil cells. Long-term treatment for an underlying health condition may be necessary if your low eosinophil count does not return to normal on its own.


How can I keep my eosinophils healthy?

Take steps to keep your eosinophil cells healthy by:

  • Avoiding allergens.
  • Eating a well-balanced diet and cooking food to its recommended internal temperature.
  • Limiting alcohol intake.
  • Practicing proper hygiene like washing your hands regularly.

Additional Common Questions

What are acidophils?

Acidophils are a less common name to identify eosinophils. The name “acidophils” comes from the term “acidophilic” (acid-loving), which specifically relates to how the granules in eosinophil cells change color when you add an acidic stain dye to the sample of cells under a microscope. The stain turns the cells a shade of pink or purple, making them easier to see.

A note from Cleveland Clinic

Eosinophils are an important part of your immune system to defend your body from outside invaders. Your healthcare provider will track the health of your cells through a blood test if they suspect your eosinophils are out of a normal range. Often, a low eosinophil count does not pose a threat to your overall health because other cells will compensate for the missing eosinophils to help your body function.

Medically Reviewed

Last reviewed on 07/05/2022.

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