Used in hair dye formulations as a coupling agent to produce a range of permanent and semi-permanent hair colors. It reacts with other dye intermediates, such as phenylenediamines, in oxidative conditions to form colored compounds. Its sulfate salt form improves stability and solubility in aqueous cosmetic preparations. Commonly found in commercial hair color products due to its effectiveness in achieving natural-looking shades and good skin compatibility when formulated properly.