What a patch test is actually for

PPD is the compound that makes permanent colour permanent. A small number of people react to it, and a reaction can arrive after years of using the same shade without trouble — sensitisation builds.

So: a dab behind the ear, forty-eight hours before, every time your colour changes or if it has been more than six months. It takes two minutes and we will not colour you without it.

We know it is inconvenient. The alternative is a hospital, and it has happened to salons we know.