Why now? Granted, p-phenylenediamine (PPD) has been the leading permanent hair coloring agent or oxidative hair dye in most of the Western world since its introduction in the 1880s, [1] and it has ...

Background: Finding alternative hair dyes for individuals allergic to para-phenylenediamine (PPD ... to PTDS who subsequently used a PTDS dye free of PPD tolerated these products.

hydrogen peroxide and p-phenylenediamine. Ammonia, an alkaline chemical, raises the pH level of the hair. This then pulls apart layers of hair's proteins, so that the dye can access the hair shaft ...