Forty-eight hours, every time

How we work

Why we will lose the booking instead

Permanent hair colour contains oxidative dyes, principally paraphenylenediamine and its relatives, which are well-documented causes of allergic contact reactions. Most are unpleasant rather than dangerous: itching, swelling, weeping skin around the hairline. A minority are serious, and a small number involve airway swelling. Every manufacturer's instruction therefore requires an allergy alert test at least forty-eight hours before the service, and insurers make it a condition of cover.

It gets skipped because the pressure to skip it is enormous and always sympathetic. Someone has an event tomorrow, their regular salon has closed, they have been colouring for fifteen years without incident. All of that is true and none of it changes the chemistry: sensitisation can develop at any time, including after years of uneventful colouring, which is precisely why the test is per-service and not once in a lifetime.

There is a particular risk worth naming because clients rarely connect it. Black henna temporary tattoos, the kind sold at markets and on holiday, frequently contain paraphenylenediamine at high concentrations. Someone who has had one may be sensitised without knowing, and a first permanent colour afterwards can produce a far worse reaction than it otherwise would. So we ask. It is one question at a consultation and it occasionally changes the entire plan.