P-Phenylenediamine

P-phenylenediamine (PPD) is a synthetic aromatic amine compound primarily used as a colorant in permanent and semi-permanent hair dye formulations. It is not commonly found in skincare products, but rather in hair colouration systems where it serves as an oxidative dye precursor.The ingredient works by undergoing oxidation when mixed with a developer, which allows it to penetrate the hair shaft and create lasting colour. In the context of skincare, PPD is relevant mainly for those who use hair dyes and may experience skin contact through application or occupational exposure.

PPD functions as a dye precursor that oxidises in the presence of hydrogen peroxide (the developer). This chemical reaction creates larger, coloured pigment molecules that bind within the hair shaft. When PPD comes into contact with skin, it can penetrate the stratum corneum and undergo similar chemical transformations, which is relevant to understanding potential allergic responses rather than skincare benefits.

PPD is not an ingredient to intentionally use in skincare. If you use hair dyes containing PPD, follow product instructions carefully, perform a patch test before application, and minimise skin contact during application. Wear gloves and avoid leaving the dye on longer than recommended.

PPD is a known contact allergen and can cause allergic contact dermatitis in susceptible individuals. Even if you have not previously reacted, sensitisation can develop with repeated exposure. Always patch test hair dyes before full application.