Used in hair dye formulations as a coupler to produce a range of permanent and semi-permanent shades, especially natural brown and black tones. It reacts with primary intermediates like p-phenylenediamine in oxidative dyes to form larger colored molecules that remain in the hair. Its structure allows for fine-tuning of hue and intensity, making it valuable in professional and consumer hair coloring products. Also found in some dye systems for eyebrows and eyelashes. Requires careful handling due to potential skin sensitization.