Permanent hair dyes are a popular choice for achieving bright, long-lasting hair colour. Many of these products contain a chemical called p-phenylenediamine, commonly known as PPD. This ingredient is ...

The vast majority of reactions to hair-dye products are caused by PPD. [4–6] In past years, PPD was used in permanent hair dyes but not in semipermanent dyes. More recently, PPD has been used in most ...