Azo dyes refer to dyes that contain at least one azo group in their chemical structure. The azo group is often connected to one or more aromatic ring systems to form a conjugated system, which serves as the chromophore of the dye, and they can produce almost all colors. Azo dyes are the most widely used synthetic dyes. They are not only used in the printing and dyeing of textiles but also in the coloring of leather, paper, food, etc. It should be noted that not all azo dyes are prohibited. Only those azo dyes that can release more than twenty carcinogenic aromatic amines specified by regulations after reduction are banned.