Blood Count

Eosinophils – White Blood Cells Linked to Allergy and Parasites

Eosinophils are a specialized type of white blood cell that plays a role in defending against parasites and mediating allergic reactions. They normally make up 1–4% of circulating white blood cells. Elevated eosinophil counts often point to allergic conditions, parasitic infections, or chronic inflammatory diseases. The test is part of a differential white blood cell count.

Why Test Eosinophils?

Eosinophil testing is recommended when investigating allergic conditions (asthma, hay fever, eczema), parasitic infections, unexplained skin rashes, chronic inflammatory diseases, or certain blood disorders. It helps determine whether an allergic or parasitic component underlies symptoms.

What Do High Eosinophils Levels Mean?

Elevated eosinophils (eosinophilia) commonly indicate allergic conditions such as asthma, hay fever, or eczema. Other causes include parasitic infections, drug reactions, autoimmune diseases, and rare conditions like hypereosinophilic syndrome.

What Do Low Eosinophils Levels Mean?

Low eosinophils (eosinopenia) are common during acute infections or stress and usually not clinically significant on their own. Corticosteroid use can also suppress eosinophil counts.

Symptoms to Watch For

  • Allergic symptoms (sneezing, itching, nasal congestion)
  • Asthma or wheezing
  • Skin rashes or eczema
  • Abdominal pain (with parasitic infections)
  • Fatigue
  • Joint or muscle pain

Who Should Get Tested?

  • People with persistent allergy symptoms
  • Those with suspected parasitic infections
  • Patients with unexplained skin rashes or eczema
  • Individuals with chronic asthma or respiratory issues
  • Anyone being evaluated for eosinophilic disorders

How to Prepare for Your Test

No special preparation is needed. Bring valid ID to your appointment.

Frequently Asked Questions

What is a normal eosinophil count?
Normal eosinophils are typically 0.04–0.4 × 10⁹/L, making up 1–4% of white blood cells. Counts above 0.5 × 10⁹/L are considered eosinophilia.
Can food allergies cause elevated eosinophils?
Yes. Food allergies and eosinophilic gastrointestinal disorders can raise eosinophil counts, sometimes concentrated in the gut lining rather than the blood.
Are eosinophils the same as basophils?
No. Both are granulocytes (white blood cells with granules), but eosinophils primarily target parasites and mediate allergic inflammation, while basophils release histamine and play a role in immediate allergic reactions.
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Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.

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Medical Disclaimer

The information on this page is provided for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Wellth provides health information and testing services but is not a substitute for clinical care. Always consult a qualified healthcare provider if you have questions about a medical condition. If you are experiencing severe or urgent symptoms, contact your doctor or call 1177 Vårdguiden. Blood test results should be interpreted by a qualified healthcare professional in the context of your complete medical history.