Used primarily in hair dye formulations as an intermediate for producing permanent and semi-permanent hair colors. It reacts with other compounds, such as couplers and oxidizing agents, to form larger colored molecules that deposit in the hair shaft. Provides warm, reddish-brown to auburn shades depending on concentration and formulation. Also found in some photographic developers due to its reducing properties. Its application in cosmetics is limited to low concentrations due to sensitization concerns.