What does the term "oxidation" refer to in hair coloring?

The term "oxidation" in hair coloring specifically refers to a chemical reaction that develops color. In the context of hair color products, particularly those that contain developers or bleaching agents, oxidation occurs when alkaline agents open the hair cuticle and enable the color molecules to penetrate the hair shaft.

During this process, the developer, which typically contains hydrogen peroxide, reacts with the dye precursors (or oxidation dyes) present in the hair color formulation. This reaction leads to the formation of larger pigment molecules that become trapped within the hair cortex, resulting in permanent hair color. Additionally, oxidation is essential for altering the natural pigment of the hair, making it lighter or allowing for changes in hue.

This understanding highlights the importance of oxidation in achieving the desired color and longevity in hair coloring services. In contrast, other options provided do not relate to the chemical processes involved in hair coloring, making them irrelevant to the definition of oxidation in this context.