What chemical agent is used in lighteners to decolorize hair?

• A. Ammonium persulfate or hydrogen peroxide
• B. Sodium hydroxide
• C. Urea
• D. Citric acid

Answer: (A)

Lightening hair works by oxidizing the pigment melanin in the cortex. The oxidizing power comes from hydrogen peroxide, which supplies reactive oxygen that breaks down melanin molecules. Ammonium persulfate is a common co-oxidizer that speeds up the reaction and helps open the hair cuticle so the pigment can be reached and oxidized more efficiently. Together, they produce the strong oxidation needed to decolorize hair.

Other substances listed don’t perform this bleaching action: sodium hydroxide is an alkali used in relaxing processes, not in decolorizing pigment; urea is mainly a humectant/moisturizer; citric acid is used to adjust pH and act as a mild acid, not to oxidize melanin.