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Eosinophilia

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eosinophilia definition evaluation causes Merck Manual

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https://www.merckmanuals.com/professional/hematology/eosinop…

Eosinophilia means an increased absolute eosinophil count (AEC) in peripheral blood, usually >500 cells/µL.
SeverityAEC
Mild500-1,500/µL
Moderate1,500-5,000/µL
Severe>5,000/µL
Eosinophils are white blood cells involved in allergic inflammation and defense against helminth parasites. - The Washington Manual of Medical Therapeutics, p. 428

Common causes

  1. Allergic or atopic disease: asthma, allergic rhinitis, eczema, urticaria.
  2. Drug reactions: antibiotics such as penicillins/cephalosporins or sulfonamides, NSAIDs, anticonvulsants, and others. Severe drug reactions such as DRESS can cause eosinophilia with fever, rash, hepatitis, nephritis, or lung disease.
  3. Parasitic infection, especially tissue-invasive helminths: Strongyloides, hookworm, schistosomiasis, filariasis, toxocariasis, trichinellosis.
  4. Autoimmune/inflammatory disorders: eosinophilic granulomatosis with polyangiitis and some connective-tissue diseases.
  5. Endocrine disease: particularly adrenal insufficiency (Addison disease).
  6. Cancer or clonal hematologic disease: Hodgkin lymphoma, T-cell lymphoma, myeloproliferative neoplasms, chronic eosinophilic leukemia.
  7. Idiopathic eosinophilia: considered only after primary and secondary causes are excluded.

Hypereosinophilic syndrome

Consider hypereosinophilic syndrome (HES) if AEC is ≥1,500/µL on repeated testing, no secondary cause is found, and there is evidence of eosinophil-related organ injury. It may affect the heart, lungs, nervous system, skin, gastrointestinal tract, or kidneys. Cardiac disease is especially important. - The Washington Manual of Medical Therapeutics, p. 428

Evaluation

The approach depends on the clinical context:
  • Repeat CBC with differential and calculate the AEC, not just the eosinophil percentage.
  • Review all medicines, supplements, and recent new drugs.
  • Ask about asthma/allergy symptoms, rash, fever, weight loss, travel, exposure to soil or contaminated food/water, and pet/contact history.
  • Directed tests may include peripheral smear, liver/kidney tests, stool or parasite testing, Strongyloides serology, chest imaging, IgE, and hematology testing if persistent or marked.
  • For persistent unexplained moderate-to-severe eosinophilia, assess for organ involvement, sometimes including ECG/echocardiography and specialist evaluation.
Do not start systemic corticosteroids without considering Strongyloides in someone with relevant tropical/subtropical exposure, because steroids can trigger life-threatening disseminated infection. The Merck Manual review also advises cause-directed testing and treatment.

When urgent assessment is needed

Seek prompt medical review for eosinophilia with chest pain, breathlessness, fainting, new neurologic symptoms, severe rash or facial swelling, high fever, jaundice, abdominal pain, rapidly rising AEC, or AEC ≥1,500/µL that persists.
Treatment is of the underlying cause. Mild, asymptomatic eosinophilia may only need repeat monitoring. Recent review evidence includes a pediatric diagnostic-algorithm systematic review (PMID 38695861); adult assessment still relies mainly on clinical context and ruling out reactive, drug-related, parasitic, and clonal causes.

The report says 8%

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eosinophil percentage absolute eosinophil count calculation CBC evaluation

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eosinophilia

An eosinophil percentage of 8% is mildly elevated in many laboratories, but the important result is the absolute eosinophil count (AEC).
AEC = total WBC count × 8%
Examples:
  • WBC 5,000/µL: AEC = 400/µL, usually not eosinophilia
  • WBC 8,000/µL: AEC = 640/µL, mild eosinophilia
  • WBC 15,000/µL: AEC = 1,200/µL, still mild but more meaningful
Eosinophilia is generally defined as AEC >500/µL. A percentage can look high simply because the other white-cell types are lower, so it should not be interpreted alone. - Goldman-Cecil Medicine defines eosinophilia by the absolute count rather than percentage.
Please share the report’s total WBC/TLC and, if listed, the absolute eosinophil count. Common benign explanations include allergy, asthma, eczema, a recent medication reaction, or a parasitic infection, depending on symptoms and exposures.
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