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Eosinophil count (peripheral blood)

Published: August 9, 2026Updated: August 16, 2026

This test measures the number of eosinophils, a type of white blood cell, in your blood. Eosinophils help fight infections and respond to allergies and inflammation.

Quick summary

["Eosinophils help protect your body from harmful substances and infections."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
7396-5
Short code
Helminthosporium IgG Qn
Synonyms
Helminthosporium IgG Qn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Are Eosinophils?

Eosinophils are a type of white blood cell that play a key role in defending your body against parasites, allergies, and certain infections. They release chemicals that help fight off harmful organisms and reduce inflammation. When levels are too high or too low, it may signal underlying health concerns.

Why Might You Need This Test?

Your doctor may order this test to diagnose or monitor conditions such as allergies, asthma, parasitic infections, certain cancers (like leukemia), or autoimmune diseases. High eosinophil counts can also be linked to conditions like eosinophilic esophagitis or certain lung diseases.

Common Conditions Monitored

Elevated eosinophil counts may indicate allergic reactions, parasitic infections, or chronic inflammatory conditions. Low counts could suggest immune system issues or certain blood disorders. Your doctor will consider your symptoms and medical history to interpret results.

How Is This Test Performed?

A blood sample is taken from a vein in your arm. The sample is then analyzed in a lab to count the number of eosinophils among your white blood cells. The results are usually available within a few days.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Eosinophil blood test

Frequently asked questions

Why do eosinophils rise or fall in my blood?
Eosinophil levels can rise due to allergies, infections (like parasites), or inflammatory conditions. They may fall due to immune system disorders, certain medications, or severe infections. Your doctor will review your symptoms and test results to determine the cause.
What do my test results mean?
Results alone don’t provide a diagnosis. High eosinophil counts may suggest allergies, asthma, or parasitic infections, while low counts could indicate immune dysfunction or blood disorders. Your doctor will discuss these findings with you and may recommend further testing.
Can I change my diet or lifestyle before the test?
No special preparations are needed for this test. However, if you’re on medications that affect white blood cells (like steroids), let your doctor know before the test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy