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 or parasites. Your body is host to five different
kinds of white blood cells. Your bone marrow makes all five kinds of white
Each white blood cell lives anywhere from several hours to 12
days and then a new one replaces it. The average lifespan of a white blood cell
is five days. How many white blood cells and which type you have in your body
can give doctors a better understanding of your health. Elevated levels of
white blood cells in your blood are a good indicator that you have an illness
or infection. Elevated levels mean your body is sending more and more white
blood cells to fight off infections.
An eosinophil count is
a type of blood test that measures the quantity of eosinophils in your body. An eosinophil is a type of white
blood cell. An eosinophil count typically helps your doctor confirm a diagnosis
rather than make a diagnosis.
Eosinophils have two distinct functions in your immune system. They
destroy invading germs like viruses, bacteria, or parasites such as Giardia and pinworm. Eosinophils also
create an inflammatory response, especially if an allergy is involved.
Inflammation is neither good nor bad. It helps isolate and
control the immune response at the site of an infection, but it also damages
the tissue around it. Allergies are immune responses that often involve chronic
inflammation. Eosinophils play a significant role in the inflammation related
to allergies and asthma.
Why Do I Need an Eosinophil Count?
Your doctor may recommend an eosinophil count if you already had
a white blood count differential and the results were abnormal. A white blood
count differential test 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 and if you have abnormal cells that occur with various diseases.
Your doctor may also order this test to help confirm the
diagnosis of certain diseases or conditions, such as:
- an extreme allergic reaction
- the initial stages of Cushing’s disease, which
is a disorder caused by too much of the steroid hormone cortisol
- a parasitic infection
How Do I Prepare for an Eosinophil Count?
There are no special preparations necessary for this test. You should
inform your doctor if you’re taking any blood-thinning drugs such as warfarin
(Coumadin). Your doctor may advise you to stop taking certain medications.
Medications that may cause you to have an increased eosinophil
- appetite suppressants
- interferon, which is a drug that helps treat
- some antibiotics
- laxatives that contain psyllium
Be sure to mention any current medication you’re taking to your
doctor before the test.
What Happens During an Eosinophil Count?
A healthcare provider will take a sample of blood from your arm
by following these steps:
- First, they’ll clean the site with a swab of
- They’ll then insert a needle into your vein and
attach a tube to fill with blood.
- After drawing enough blood, they’ll remove the
needle and cover the site with a bandage.
- They’ll then send the blood sample to a
laboratory for analysis.
What Do the Results Mean?
A normal blood sample reading will show fewer than 350 eosinophil
cells per microliter of blood.
If you have over 350 eosinophil cells per microliter of blood,
then it indicates you have a disorder known as eosinophilia. This can be due to any of the following:
- an allergic reaction to parasitic worms
- an autoimmune disease
- seasonal allergies
- ulcerative colitis
- scarlet fever
- Crohn’s disease
An abnormally low eosinophil count can be the result of
intoxication from alcohol or excessive production of cortisol, which is a steroid produced
naturally in the body.
What Are the Complications Associated with
an Eosinophil Count?
An eosinophil count uses a standard blood draw, which you have
likely had many times in your life.
As with any blood test, there are minimal risks of experiencing
minor bruising at the needle site. In rare cases, the vein may become swollen
after blood is drawn. This is called phlebitis. You can treat this condition by
applying a warm compress several times each day. If this isn’t effective, you
should consult your doctor.
Excessive bleeding could be a problem if you have a bleeding
disorder or you take blood-thinning medication such as warfarin (Coumadin) or
aspirin. This requires immediate medical attention.
What Happens After an Eosinophil Count?
If you have an allergy or parasitic infection, your doctor will
prescribe a short-term treatment to alleviate symptoms and revert your white
blood cell count to normal.
If your eosinophil count indicates an autoimmune disease, your
doctor may want to conduct more tests to determine which type of diseases you have.
They may then prescribe corticosteroids.