Indeed, the active ingredient of hair dye is p-phenylenediamine, but p-phenylenediamine is toxic but not a carcinogen. According to the U.S. Environmental Protection Agency (EPA), acute exposure symptoms of p-phenylenediamine include severe dermatitis, eye irritation and tearing, asthma, gastritis, renal failure, dizziness, tremors, convulsions and coma. Chronic exposure symptoms include contact dermatitis. Animal experiments have found that long-term exposure to p-phenylenediamine in the diet can lead to weight loss, but no other clinical symptoms of poisoning have been found.