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Eosinophil count (qualitative or semi-quantitative blood smear evaluation)

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

This test checks the number of eosinophils in your blood, a type of white blood cell that helps fight certain infections and reactions to allergens.

Quick summary

["Eosinophils may rise in response to allergies, infections, or other immune responses."]

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

Key facts at a glance

LOINC
71661-3
Short code
Eosinophil NFr.DF CSF Manual
Synonyms
Eosinophil NFr.DF CSF Manual
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test to investigate symptoms like persistent itching, skin rashes, asthma, or unexplained infections. It can also help diagnose conditions like allergies, parasitic infections, or certain autoimmune diseases.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood, similar to a routine blood test. The blood sample is then examined under a microscope to count eosinophils.

What the Results Mean

Results are qualitative (yes/no) or semi-quantitative (approximate count). High levels may suggest allergies, asthma, or parasitic infections, while low levels might indicate immune suppression or other conditions. Your doctor will discuss findings in relation to your symptoms.

Common Conditions Linked to Eosinophil Levels

Elevated eosinophils are often seen in allergic reactions, asthma, parasitic infections (e.g., hookworm), or certain cancers like leukemia. Low eosinophil counts can occur with stress, infections, or medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical significance: Eosinophils play a role in allergic and parasitic responses. Elevated counts may guide treatment for allergies, asthma, or infections, while low counts can signal immune dysfunction or other underlying issues.

Short name

Eosinophil test

Frequently asked questions

What causes eosinophils to rise in the blood?
Eosinophils can increase due to allergies, asthma, parasitic infections, certain cancers (e.g., leukemia), or autoimmune diseases. Stress, infections, or medications may also temporarily lower them.
How long does it take to get results?
Results are typically available within 1–2 business days, depending on lab processing times. Your doctor will contact you once they’re ready for review.
Can I eat or drink before this test?
No special diet is required. You can eat and drink normally, but avoid alcohol the evening before if your doctor advised it.
  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