Platform
Company
Complete Blood Count
Review status
Currently under review
Pending specialist review and validation.
This test reports the percentage of white blood cells that are eosinophils, based on a manual review of a stained blood smear. A trained technologist examines the slide under a microscope and classifies cells to estimate how many are eosinophils compared with all white blood cells counted.
Eosinophils are immune cells that help your body respond to allergies, asthma, certain infections, and other inflammatory conditions. The manual percent is often used when an automated analyzer flags an abnormal result, when cells look unusual, or when a more detailed review is requested as part of a complete blood count with differential.
Knowing your eosinophil percentage helps your clinician look for causes of allergic symptoms, asthma flares, drug reactions, skin conditions, and some parasitic infections. It can also provide clues to autoimmune or inflammatory disorders and, less commonly, specific blood diseases.
Doctors may order this test to confirm or clarify automated results, to investigate persistent symptoms such as wheezing or rash, to evaluate unexplained lab abnormalities, or to monitor response to treatments that affect eosinophils, including corticosteroids or targeted biologic medicines.
Your eosinophil percent is interpreted together with your total white blood cell count, the absolute eosinophil count, your symptoms, and your medical history. A higher than expected percent can be seen with allergies, asthma, certain infections, medication reactions, and some blood or tissue disorders. A lower percent is usually not worrisome by itself and may reflect stress, recent illness, or medications that suppress eosinophils.
Because a percent can shift when other white blood cell types change, your clinician may focus on the absolute eosinophil count and may suggest repeat testing if you were ill or taking certain medicines. Depending on your situation, follow up could include a medication review, allergy assessment, stool or blood tests for parasites, or referral to a specialist.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Eosinophils vary with daily rhythms and cortisol levels; counts tend to be lower in the morning or during physiologic stress, which can influence the measured percent.
Corticosteroids, epinephrine, and certain biologic drugs that target eosinophils can lower eosinophil levels, while some antibiotics or new medications can trigger allergic reactions that increase them.
Bacterial infections and acute inflammation often increase other white cells, which can make the eosinophil percent appear lower even if the absolute number has not changed.
Seasonal allergies, eczema flares, and uncontrolled asthma can raise eosinophils; keeping symptoms stable and sharing flare timing helps with interpretation.
Recent travel, undercooked food, or freshwater exposure can be relevant, since some parasitic infections stimulate eosinophils and affect results.
Delays in making the blood smear, clotted samples, or poor staining can hinder accurate manual classification and slightly skew the reported percent.
Physiologic changes during pregnancy can lower eosinophils, with possible rebound after delivery; inform your clinician if you are pregnant or recently postpartum.
Intense exercise, surgery, or acute stress responses can transiently reduce circulating eosinophils, which may lower the measured percentage.
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