Which stain is used to identify eosinophils and may indicate an allergic reaction?

The Hansel stain is specifically designed to highlight eosinophils in various biological samples, including urine. Eosinophils are a type of white blood cell that plays a significant role in the body's allergic responses and in combating parasitic infections. A notable characteristic of eosinophils is their affinity for certain stains due to the presence of granules that contain various proteins and enzymes.

When using the Hansel stain, eosinophils exhibit bright blue granules, which can help in the identification of these cells under a microscope. The presence of eosinophils in urine may indicate an allergic reaction or inflammation, particularly in conditions like eosinophilic cystitis or certain drug reactions.

Other staining methods mentioned could identify different components or cell types but are not utilized for specifically identifying eosinophils associated with allergic reactions. For example, Prussian blue is used to detect iron deposits, Toluidene blue primarily stains mast cells and may identify metachromatic granules, and Oil red is used for detecting lipids rather than white blood cells.