m-Phenylenediamine sulfate is primarily used in the hair dye industry as a key ingredient in oxidative hair coloring products. It acts as a precursor in the formation of dye molecules, reacting with other compounds to produce a wide range of colors. This chemical is also employed in the production of azo dyes, which are utilized for coloring textiles, leather, and paper. Additionally, it finds application in the synthesis of certain polymers and resins, contributing to their structural and functional properties. In analytical chemistry, it serves as a reagent for detecting specific substances due to its reactive nature. Its use requires careful handling due to potential health hazards.