Para-phenylenediamine (PPD), commonly used in permanent hair colouring, is added to natural henna to boost colour intensity ...

Henna can be applied like any ordinary hair colouring kit, and it has a half-permanent effect that, on average, lasts about ...

Semi-permanent vegetable dyes such as henna are recommended by the NHS as a safe alternative if you do not want to use chemical dyes on your hair. The main thing to remember is that your hair may ...