Widely used in hair dye formulations as a primary intermediate (developer) to produce stable, long-lasting dark colors, particularly natural-looking brown to black tones. It undergoes oxidation in the presence of peroxide to form reactive species that couple with couplers, enhancing shade intensity and improving color uniformity. Offers good compatibility with oxidative dye systems and helps maintain hair condition during coloring. Its sulfate form improves solubility and stability in aqueous solutions, making it suitable for ready-to-use products. The modified structure, including the hydroxyethyl group, helps reduce irritation compared to some other aromatic amines.