p-Phenylenediamine is one of the simplest aromatic diamine primarily used as a component of engineering polymers, composites, dye intermediate and as a hair dye. p-Phenylenediamine is easily oxidized, and for this reason derivatives of p-Phenylenediamine are used as antiozonants in the production of rubber products. The substituents, naphthyl, isopropyl etc. affect the effectiveness of their antioxidant roles as well as their properties as skin irritants. Acute (short-term) exposure to high levels of p-phenylenediamine may cause severe dermatitis, eye irritation and 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. No information is available on the reproductive, developmental, or carcinogenic effects of p-phenylenediamine in humans. EPA has not classified p-phenylenediamine with respect to carcinogenicity.