Hair dyes with modified paraphenylenediamine (PPD), which is in development currently, could help completely avoid allergic reactions, a negative feature often associated with hair dyes. According to a study published in ACS Sustainable Chemistry and Engineering, a team of international researchers have developed hair dyes that are less likely to cause allergic reactions in users by modifying the aromatic amine core of paraphenylenediamine (PPD). Study researcher Paul Bigliardi, professor and director of the dermato-allergy division at University of Minnesota Medical School, pointed out that PPD often binds proteins in the user’s skin and can cause eczema, facial swelling, allergic contact dermatitis and other reactions including serious systemic toxicity. He said that the modified versions of the dyes were found to be producing significantly reduced inflammatory response in cells compared with PPD and also did not fade away after 3 weeks of daily washing, while expressing their hope that their dyes would prove to be beneficial to a large section of consumers.