What is the main ingredient in bleach used for hair lightening?

The main ingredient in bleach used for hair lightening is hydrogen peroxide. This chemical acts as an oxidizing agent, breaking down the natural pigment in the hair strand, which effectively lightens the hair color. When hydrogen peroxide is applied to the hair, it penetrates the hair shaft and reacts with the melanin (the pigment responsible for hair color), leading to a gradual lightening effect.

Hydrogen peroxide is often combined with ammonia in hair bleach formulations to enhance its effectiveness; ammonia opens the hair cuticle, allowing the hydrogen peroxide to work more effectively. However, it is the hydrogen peroxide that is primarily responsible for the lightening action itself.

In contrast, ammonia is not the lightening agent but rather acts to facilitate the process by altering the pH. Alcohol and sodium chloride do not contribute to the hair lightening process in the same way; alcohol is typically used as a solvent or preservative, and sodium chloride (commonly known as table salt) has no role in bleaching hair.