An absolute eosinophil count is a blood test that measures the number of eosinophils present in a blood sample, according to MedlinePlus. Typically, a health care worker draws blood from a vein with a needle for examination under a microscope to determine the number of eosinophils.
A lab technician counts the number of eosinophils present per 100 white blood cells and then multiples by the total number of white blood cells to calculate the absolute eosinophil count, explains MedlinePlus. A normal result is less than 350 eosinophils per microliter. An abnormally high result may be due to asthma, autoimmune diseases, eczema, hay fever or leukemia.