Used in hematology laboratories to count eosinophils in blood samples. The dilution fluid lyses red blood cells and other white blood cells selectively, leaving eosinophils intact and easily identifiable under the microscope. This allows for accurate manual counting using a hemocytometer. It is essential in diagnosing and monitoring allergic reactions, parasitic infections, and certain inflammatory conditions where eosinophil levels are elevated. The staining property of the dye in the solution enhances contrast, making eosinophils clearly visible due to their bright red-orange granules.