Para PhenyleneDiamine (PPD), is a low toxicity diamine used in hair dyes , textile dyes, leather dye, dyes intermediates, pigments , as a component of engineering polymers and composites, aramid fibers, rubber chemicals, dyeing furs, chemical intermediate for N,N'-Disubstituted-p-Phenylene diamines , component of gasoline antioxidants , for accelerating vulcanization and photographic products. PPD is selected for the outstanding properties it imparts, including high temperature stability, high strength, and chemical and electrical resistance.

This aromatic amine compound is used in almost every hair dye/ hair colour available in the market, regardless of brand. The darker the colour, usually, the higher the concentrations. Even the so-called natural, herbal, kali mehndi, while ammonia-free, contain PPD.