Illinois Cosmetology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Hydrogen peroxide functions primarily as a developer that lightens hair. When used in the context of hair coloring, hydrogen peroxide acts as an oxidizing agent that opens the hair cuticle and allows the color to penetrate into the hair shaft. This oxidation process breaks down the natural pigments in the hair, effectively lightening the existing color.

Once the cuticle is open, the dye molecules can enter the hair and bond with the structural proteins, which helps to achieve the desired shade. This property of hydrogen peroxide makes it essential in both permanent hair color applications and in lightening treatments.

In contrast, the other choices represent different functions that do not accurately describe hydrogen peroxide’s role in hair coloring. For example, while alkalinity can facilitate the opening of the hair cuticle, it is not the primary function of hydrogen peroxide. Conditioning agents would typically refer to substances that improve the feel and manageability of hair rather than effects on color, and color enhancers would aim to enrich the existing color rather than lightening it. Therefore, identifying hydrogen peroxide specifically as a developer highlights its critical role in the hair coloring process.