Eosinophils (abs.)
Immune system healthAlso known as: absolute eosinophil count, AEC
The absolute count of eosinophils per liter of blood.
Eosinophils are white blood cells involved in fighting parasitic infections and mediating allergic responses. The absolute count is more clinically meaningful than the percentage, as it directly reflects the body's eosinophilic activity regardless of total white blood cell levels.
Reference range
Source: lab benchmark
Reference ranges may vary between labs and assays. Always interpret results with your healthcare provider.
Why this matters
Eosinophils are your body's specialized defenders against parasites and moderators of allergic inflammation. Optimal range is generally below 4-5%. Elevated levels (eosinophilia) commonly indicate allergies, asthma, eczema, or parasitic infections. Very high levels might suggest autoimmune conditions or certain cancers.
When activated, eosinophils contribute to symptoms like wheezing, skin rashes, and nasal congestion. Monitoring helps assess allergic disease activity and treatment response.
How this connects to other biomarkers
- Eosinophilia (> 0.5 × 10⁹/L) suggests atopy/allergy, parasitic infection, drug reaction, eosinophilic GI/respiratory disease, or eosinophilic granulomatosis with polyangiitis (EGPA — a rare autoimmune blood-vessel disease).
- Marked persistent eosinophilia (> 1.5 × 10⁹/L) for > 6 months defines hypereosinophilic syndrome and warrants tissue and end-organ workup.
- Low Eosinophils accompany Cortisol elevation (acute stress, exogenous steroids).
How often should I test Eosinophils (abs.)?
Most adults benefit from yearly absolute eosinophil count testing as part of a CBC differential. When tracking allergic or eosinophilic conditions, retest at 3 to 6 months.
At baseline / for screening: Once every 12 months from age 30 as part of a CBC with differential.
When monitoring an intervention or change: Retest 3 to 6 months when actively tracking allergic, asthmatic, or eosinophilic conditions. After starting or adjusting treatment (inhaled corticosteroids, biologics like dupilumab or mepolizumab, antihistamines), expect 6 to 12 weeks for a meaningful shift. Eosinophil counts have a diurnal rhythm, so standardize timing across draws for reliable trends.
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