What chemical process is used to lighten hair?

The correct answer is bleaching, as this chemical process is specifically designed to lighten hair by stripping away the natural pigment, melanin. Bleaching agents often contain hydrogen peroxide or other lightening compounds that penetrate the hair shaft and oxidize the melanin, resulting in a lighter hair color. This process can lift the color of the hair multiple levels, making it a popular method for achieving blonde shades or for creating a lighter base before applying another hair color.

Dyeing, on the other hand, typically involves adding color to the hair rather than removing it. Highlighting is a technique that involves lightening selected strands of hair, which can create a multi-dimensional effect, but it is not the same as the overall lightening that occurs with bleaching. Perming involves a chemical process to alter the texture of the hair, creating curls or waves, and does not contribute to the lightening of hair color.