Which chemical process is used to lighten hair color?

The process used to lighten hair color is oxidation. This reaction involves the use of oxidizing agents, such as hydrogen peroxide, which lift the color pigments from the hair. During oxidation, the melanin in the hair, which is responsible for its natural color, is broken down and lightened. This chemical process alters the structure of the hair color molecules, leading to a lighter shade.

In the context of hair coloring, oxidation not only lightens the existing color but can also allow for the introduction of new colors through the application of permanent hair dyes, which rely on oxidizing agents to develop the desired tone. This is why understanding oxidation is crucial for those working in cosmetology, as it directly influences the outcomes of hair lightening and dyeing techniques.