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 precursors, such as primary intermediates, to form larger colored molecules that deposit in the hair shaft. Its amino and hydroxyl groups contribute to solubility and binding efficiency, enhancing color intensity and durability. Commonly found in oxidative hair color systems due to its ability to generate natural-looking brown to black shades. Also helps improve dye stability and reduce skin irritation compared to other aromatic amines.