Novel Insight into the Staining and Counterstaining Properties of Lawsonia inermis (Henna) in Histological Preparations

Lawsonia inermis commonly called Henna is a naphthoquinone‐rich plant which is exploited as a natural dye for hair colouring and cosmetic purposes for nails and skin. Histological staining properties of Lawsonia inermis was studied using Wistar rat specimens of skin, liver, brain, kidney and intestine fixed in neutral buffered formalin and prepared for light microscopy. Stain was prepared as 0.5% extract of leaves of Lawsonia inermis dissolved in 5% aqueous alcohol and mordanted with potassium alum (aluminium potassium sulphate). The tested extract stained cell cytoplasm brown and gave consistent reproducible results. Nuclei did not pick up the stain suggesting that it is an acidic stain similar to eosin. Stain showed great affinity for keratin and muscle cells which stained deeply. Lawsonia inermis when used as a counterstain to haematoxylin showed marked contrast and clarity which was comparable to routine H&E preparations and was heat stable. This indicates that Lawsonia inermis could be developed as an acidic stain or a counterstain to haematoxylin in histological techniques for highlighting structures in biological tissues.