Which statement is true about Mayer hematoxylin?

• A. It is the most preferred for IHC stains
• B. It uses mercuric oxide to form hematein
• C. It is a natural resin
• D. It dissolves in water

Answer: (A)

Mayer hematoxylin is a water-soluble, mercury-free hematoxylin solution used as a nuclear counterstain, prized in immunohistochemistry for giving crisp, easily distinguishable nuclei without compromising antigen detection. The hematein pigment forms via oxidation and then complexes with a mordant (often aluminum), creating a stable stain that binds well to tissue. Because it dissolves readily in water and is formulated for aqueous staining workflows, it integrates smoothly into IHC protocols and minimizes interference with the chromogenic signals. This combination of safety (no mercury), compatibility with aqueous processing, and reliable nuclear contrast is why Mayer hematoxylin is often the preferred choice for IHC stains. It is not a natural resin, and while it is water-soluble, that solubility is part of why it’s favored in IHC, not a point against it.