Eosinophils · high result
High eosinophils: what they mean, causes and what to check next
Short answer
High eosinophils (eosinophilia) — an absolute count above about 0.5 × 10³/µL (500 per microliter), or a percentage above the lab's range (usually about 5–6%) — most often point to allergy: asthma, eczema, hay fever, food allergy or a reaction to a medication. Parasitic infection is the next common cause, especially after travel or with undercooked food or pets. Eosinophilic esophagitis and other eosinophilic gut disorders, some autoimmune and vasculitic conditions, adrenal insufficiency and certain cancers also raise it. Mild eosinophilia (500–1,500) with a clear allergic story is followed; a persistent count above 1,500 (hypereosinophilia) is investigated regardless of symptoms because eosinophils at that level can damage the heart, lungs and nerves.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Eosinophils above about 1,500 with chest pain, shortness of breath, palpitations, numbness or weakness — same-day evaluation for organ involvement
- A rising count with fever and a spreading rash after starting a new medication — same-day care (possible DRESS syndrome)
- Food lodged in the esophagus that will not pass — emergency care
What is the normal range for Eosinophils?
- age 18+: 1.00 – 4.00 %
Often reflects allergies, asthma, parasites, or certain medications.
Full reference table, citations and testing options: Eosinophils biomarker page.
What are the common causes of high Eosinophils?
- Allergic disease — asthma, eczema (atopic dermatitis), allergic rhinitis, food allergy, urticaria; the most common cause in the US
- Drug reactions — antibiotics (penicillins, cephalosporins, sulfa), NSAIDs, anticonvulsants, allopurinol; the severe form is DRESS syndrome with rash, fever and organ involvement
- Parasitic infections — strongyloides, hookworm, schistosomiasis, toxocara, filariasis; travel, immigration, undercooked meat or fish, soil exposure and pets are the clues (common gut parasites such as giardia and pinworm do not raise eosinophils)
- Eosinophilic esophagitis and gastroenteritis, celiac disease, inflammatory bowel disease
- Autoimmune and vasculitic disease — eosinophilic granulomatosis with polyangiitis (Churg–Strauss), sarcoidosis, rheumatoid arthritis, bullous pemphigoid
- Adrenal insufficiency (Addison's) — cortisol normally suppresses eosinophils
- Allergic bronchopulmonary aspergillosis, chronic eosinophilic pneumonia and other lung diseases; coccidioidomycosis in the Southwest
- Hodgkin lymphoma, T-cell lymphomas, systemic mastocytosis, chronic eosinophilic leukemia and the hypereosinophilic syndromes — uncommon, usually with persistent counts above 1,500
What symptoms go with high Eosinophils?
- Wheeze, cough, itch, rash, hives, nasal congestion with allergic causes
- Trouble swallowing or food getting stuck (eosinophilic esophagitis), abdominal pain or diarrhea after travel
- Often none — a mild elevation is frequently incidental
- Fatigue, weight loss, night sweats, shortness of breath, numbness or chest pain at high counts — the organ-damage picture of hypereosinophilia
What do clinicians usually check next?
- Confirm the absolute eosinophil count (total WBC × eosinophil %) and repeat in 4–6 weeks; many mild elevations are seasonal or transient
- A careful allergy, asthma, eczema and medication history — including supplements and anything started in the previous two months
- Travel and exposure history; stool for ova and parasites (three samples) and strongyloides serology for anyone with travel or soil exposure — strongyloides matters because steroids can make it disseminate
- Total IgE, and allergen-specific IgE panels when a specific trigger is suspected
- CRP, a metabolic panel with liver tests, and a morning cortisol if fatigue, low blood pressure or salt craving suggest adrenal insufficiency
- For counts persistently above 1,500: troponin or BNP and an echocardiogram, chest imaging, a peripheral smear, vitamin B12 and tryptase, and hematology referral for clonal testing (FIP1L1-PDGFRA)
- Gastroenterology referral with endoscopy and biopsies for swallowing difficulty, food impaction or persistent gut symptoms
Follow-up tests available at TestWell: Cortisol Test (AM) ($26.49), Vitamin B12 Test ($19.99), C-Reactive Protein Test (CRP) ($26.99), Total IgE Test (Immunoglobulin E) ($29.99), Tryptase Test ($71.99).
How do you recheck Eosinophils?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Biological Age Panel | Panel · 3 tests | $59.99 | Yes | 1–3 business days |
| General Wellness Panel | Panel · 4 tests | $49.99 | Yes | 1–3 business days |
| Blood Clotting Panel | Panel · 4 tests | $149.99 | No | 3–7 business days |
| CBC with Differential Test | Test · 14 biomarkers | $17.99 | No | 1–3 business days |
Common questions
What is a high eosinophil count?
An absolute count above about 0.5 × 10³/µL (500 per microliter), or above roughly 5–6% of white cells. 500–1,500 is mild, 1,500–5,000 moderate, and above 5,000 severe; persistent counts over 1,500 are called hypereosinophilia and are investigated even without symptoms.
What causes high eosinophils?
Allergy — asthma, eczema, hay fever, food and drug allergy — is by far the most common cause in the US, followed by parasitic infection, eosinophilic gut disorders, certain autoimmune conditions and adrenal insufficiency. Blood cancers are an uncommon cause and usually come with very high, persistent counts.
Is a slightly high eosinophil percentage a concern?
A percentage a point or two above range with a normal absolute count is almost always allergy or seasonal variation. Persistent absolute counts above 1.5 need investigation.
Can allergies or asthma raise eosinophils?
Yes — they are the most common cause, and the count tracks disease activity; it rises during pollen season or an eczema flare and falls with treatment. In asthma, an eosinophil count above about 300 is used to select patients for biologic therapies, so the number has treatment meaning.
Should I be tested for parasites?
If you have traveled to or lived in a tropical or subtropical region, eaten undercooked meat or fish, have soil exposure, or have gut symptoms — yes, with stool studies and strongyloides serology. The common US gut parasites (giardia, pinworm) do not raise eosinophils, so a negative stool test with ongoing eosinophilia points back to allergy or another cause.
How do you lower eosinophils?
Treat the cause: control the allergy or asthma, stop the responsible medication, treat the parasite. Corticosteroids lower eosinophils quickly and are used for eosinophilic organ disease — but only after strongyloides has been excluded. Newer biologics (anti-IL-5) are used for severe eosinophilic asthma and hypereosinophilic syndromes.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.