Which stain is commonly employed for counterstaining epithelial sections?

Eosin is a commonly used counterstain in histopathology, particularly for staining epithelial sections. It is an acidophilic dye that stains cytoplasmic components, collagen, and other extracellular matrix elements, providing a contrasting background to other stains, such as hematoxylin, which stains nuclear material.

The combination of hematoxylin and eosin (H&E) is the most widely used staining method in histopathology, as it grants a clear distinction between different cellular components. Hematoxylin stains the nuclei a deep blue or purple, while eosin imparts shades of pink to the cytoplasm and connective tissues. This dual staining enhances the visualization of cellular morphology and tissue architecture, making eosin an essential component for a detailed tissue examination.

Other stains mentioned, like alizarin red, aniline blue, and Giemsa, serve distinct purposes in histopathology. Alizarin red is typically used for staining calcium deposits, aniline blue for connective tissue fibers, particularly collagen, and Giemsa for blood and bone marrow analysis. These stains do not effectively fulfill the role of counterstaining epithelial sections in the same way eosin does.