Hydrogen peroxide
Also known as: Developer; peroxide; oxidant; '10 volume', '20 volume', '30 volume', '40 volume'
INCI name: Hydrogen Peroxide
What it does
The developer in permanent colour. It sets off the reaction that turns colour-formers into colour inside the hair, and lightens your natural pigment at the same time.
Benefits
Needed for any permanent colour or lightening.
Concerns & Risks
An irritant. It can sting and redden the scalp, and at high strength, with long contact or under heat it can cause chemical burns. Most published scalp burns followed bleaching or highlights; the risk is higher above about 10%, although burns have been reported at lower strengths. It is not an allergen and is not the cause of PPD-type allergic swelling. Keep it out of the eyes.
Comedogenic rating
Non-comedogenic (0)
Suitable for
Most people with an intact scalp, at the strength the pack supplies
Avoid if
Your scalp is broken, burnt or irritated; never swap in a stronger developer than the pack directs
Typical concentration
Lightening and colouring products typically use 3–6% (10–20 volume). EU maximum in hair products 12% (40 volume); labels must say 'Contains hydrogen peroxide', warn to avoid the eyes and, for hair, 'Wear suitable gloves'. India: BIS IS 8481 tests the developer's peroxide content, but we could not see the permitted range. US: no specific limit verified.