What is the role of sodium hydroxide in hair relaxers?

Sodium hydroxide plays a critical role in hair relaxers as it is used to break down the hair's natural bonds, specifically the disulfide bonds in the keratin structure of the hair. This process is essential for changing the hair's texture from curly or wavy to straight. When sodium hydroxide is applied to the hair, it alters the pH level, which in turn helps to weaken the disulfide bonds, allowing for the hair's shape to be changed during the relaxing process.

This chemical reaction effectively straightens the hair, making it more manageable for styling. The other functions listed, such as adding moisture, coloring, or enhancing shine, do not pertain to the primary action of sodium hydroxide in hair relaxers. Instead, these actions are usually achieved through separate products or ingredients designed specifically for those purposes. Thus, the ability of sodium hydroxide to break down the hair's natural bonds is pivotal in the chemical relaxation process.