Resorcinol
Also known as: 1,3-benzenediol; m-dihydroxybenzene
INCI name: Resorcinol
What it does
A 'coupler': it does not colour hair on its own but reacts with PPD-type colour-formers to shape the final shade.
Benefits
Helps permanent colours reach a wider range of natural-looking shades.
Concerns & Risks
A moderate skin sensitiser in animal tests, though allergy in people is uncommon: 0.1% of European patients patch-tested reacted to it. It was, with PPD, the most frequent sensitiser on the labels of 159 hair dyes sold in India, and it was in 89% of US home dyes in another survey. The EU's scientific committee reviewed the evidence on hormone (endocrine) effects in 2021 and still judged it safe within the current limits. EU labels must warn to rinse eyes at once if it gets in them.
Comedogenic rating
Non-comedogenic (0)
Suitable for
People without hair-dye allergy
Avoid if
You have a known resorcinol allergy or have reacted to a hair dye before
Typical concentration
EU maximum 1.25% on the head after mixing in oxidative dyes; 0.5% in hair lotions and shampoos. Label must say 'Contains resorcinol'. India and US: no specific limit verified.