Used in hair dye formulations as a coupler to produce a range of natural-looking hair colors, especially in oxidative colorants. It helps achieve stable, long-lasting shades by reacting with primary intermediates in the presence of hydrogen peroxide. Commonly found in permanent and semi-permanent hair dyes, it contributes to color intensity and tone modulation, particularly in brown and black shades. Its dihydrochloride form enhances solubility and stability in acidic dye systems.