P-phenylenediamine(PPD) is part of a class of chemicals called aromatic amines,  primarily used as a dye intermediate and as a dye (e.g., hair dyes and dyes used for dyeing furs), as well as a photographic developing agent and a chemical intermediate.  It is also used as a vulcanization accelerator and as an antioxidant in rubber compounds.

Side effect :

Para-phenylenediamine is the commonest and most well-known component of hair dyes. PPD is found in more than 1000 hair dye formulations and is the most frequently used permanent hair dye component in Europe, North America and East Asia. PPD containing hair dyes have been associated with cancer and mutagenicity. Apart from that, PPD has potential toxicity which includes acute toxicity such as allergic contact dermatitis and subacute toxicity. 

Acute (short-term) exposure to high levels of p-phenylenediamine may cause severe dermatitis, eye irritation and tearing, asthma, gastritis, renal failure, vertigo, tremors, convulsions, and coma in humans.  Eczematoid contact dermatitis may result from chronic (long-term) exposure in humans.  In rats and mice chronically exposed to p-phenylenediamine in their diet, depressed body weights, but no other clinical signs of toxicity, were observed in several studies.