Mucicarmine stain is intended for the staining of mucin. Mucin is a secretion produced by a variety of epithelial cells and connective tissue cells. In certain intestinal inflammations or carcinomas, an excess of mucin is secreted by the epithelial cells.

The mucicarmine staining technique is also useful for determining the site of a primary tumor by visualizing tumor cells producing mucin in an area not containing mucin-producing cells, which means that the tumor is not affected. appeared in this area.

Mucicarmine staining is also useful for staining encapsulated fungi like cryptococcus.

The principle of mucicarmine staining is based on the presence of aluminum that forms a chelating complex with carmine. This changes the charge of the carmine molecule to a positive charge which allows it to bind to low density acidic substrates such as mucins.