Eosinophils

What it measures

White cells involved in allergy and defense against parasites. Counts help investigate allergic disease, helminth infection and drug reactions.

Specimen and preparation

• Specimen: Whole blood (EDTA)
• Tube: Lavender top
• Preparation: Counts are lowest in the morning and fall with steroid use.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Allergic disease (asthma, hay fever, eczema)
• Parasitic (helminth) infection
• Drug reactions (e.g. DRESS)
• Addison disease
• Hypereosinophilic syndrome, eosinophilic leukemia
• Hodgkin lymphoma

Causes of low values

• Corticosteroids
• Acute stress or Cushing syndrome
• Acute bacterial infection

Method

Automated differential; manual chamber count for absolute eosinophils if needed

Good to know

Counts above 1.5 ×10⁹/L persisting for weeks define hypereosinophilia and need evaluation for organ damage.

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