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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 certain infections and respond to allergies.

Quick summary

["Eosinophils help your body defend against parasites and allergic reactions."]

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

Key facts at a glance

LOINC
67835-9
Short code
Eosinophil # Plr Fetus
Synonyms
Eosinophil # Plr Fetus
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
86430
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

What Are Eosinophils?

Eosinophils are a type of white blood cell that play a role in fighting off infections caused by parasites and managing allergic responses. They also help reduce inflammation in some conditions. While they’re usually present in small amounts in healthy blood, they can increase significantly in response to certain illnesses or conditions.

Why Might Your Eosinophil Count Be Checked?

Your doctor may order an eosinophil test if you have symptoms like persistent itching, skin rashes, digestive issues, or unexplained fatigue. It’s also used to monitor conditions such as allergies, asthma, parasitic infections, or certain autoimmune diseases.

Common Reasons for Testing

Common reasons include diagnosing or managing allergic reactions, identifying parasitic infections, evaluating conditions like eosinophilic esophagitis or asthma, or checking for signs of certain cancers or inflammatory disorders.

What to Expect Before the Test

This test is typically done by taking a small blood sample from your arm. No special preparation is usually needed, but your doctor may advise fasting or avoiding certain medications if instructed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Eosinophil

Frequently asked questions

What does an elevated eosinophil count mean?
An elevated eosinophil count may suggest an allergic reaction, parasitic infection, or inflammatory condition like asthma or eosinophilic esophagitis. Your doctor will consider your symptoms and other test results to determine the cause.
What causes low eosinophil counts?
Low eosinophil counts can occur with certain medications, immune system disorders, or chronic illnesses. They may also be seen in people with severe infections or those undergoing certain treatments like chemotherapy.
How often should I get this test?
Your doctor will decide how often to check your eosinophil count based on your symptoms, medical history, and treatment plan. Regular monitoring may be needed if you have ongoing conditions like allergies or asthma.
  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