Ace the Illinois Cosmetology Exam 2025 – Glam Up and Shine Bright!

The correct answer is oxidation. During hair coloring, particularly with permanent hair dyes, an oxidation reaction occurs. This process involves the interaction of the hair dye with the natural pigments in the hair, often requiring an oxidizing agent such as hydrogen peroxide. When applied, the oxidizing agent opens up the hair cuticle to allow the color molecules to penetrate the hair shaft.

As the dye oxidizes, it forms larger color molecules that are trapped in the hair, resulting in a permanent change in color. This process not only deposits the new color but also often lightens the existing pigment in the hair, contributing to the overall change in appearance.

In contrast, reduction involves gaining electrons or decreasing oxidation states and is not a primary mechanism in hair coloring processes. Hydrolysis typically refers to the breakage of chemical bonds through the addition of water, which does not directly relate to the chemical changes involved in hair dyeing. Neutralization involves an acid and a base reacting to form water and salt and is not applicable in the context of hair coloring. Understanding these distinctions can help solidify the concept of how coloring works chemically on a molecular level.