Hematoxylin

Hematoxylin is a natural dye obtained from the heartwood of the logwood tree (Haematoxylum campechianum). In histology it is used mainly as a nuclear stain in combination with eosin (the common H&E stain). The active staining pigment is not hematoxylin itself but hematein, formed by oxidation of hematoxylin. In the presence of metal mordants such as aluminum, iron, or copper, hematein forms a complex that binds to nucleic acids and other anionic groups, staining cell nuclei blue to blue-purple and rendering them basophilic.

Eosin serves as a counterstain, coloring cytoplasmic and extracellular components pink to red, which provides contrast to the nuclei. The overall appearance in routine staining depends on pH, differentiation steps, and a blueing step performed with an alkaline solution to enhance the blue color of nuclei.

Common hematoxylin formulations include Mayer’s, Harris’, and Gill’s hematoxylin; some are pre-oxidized while others require oxidation before use. In routine practice, staining times, differentiations, and blueing steps are optimized for different tissue types. Variations exist for special stains and fluorescence methods that use hematoxylin or its derivatives.

Beyond routine H&E, hematoxylin is used as a general nuclear stain in histochemistry and as a component of various special stains. Handling and disposal follow standard laboratory safety practices for chemical dyes, with attention to documentation, storage, and institutional guidelines.