Florida Cosmetology License Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Sodium hydroxide is the primary ingredient in many hair relaxers because it is a strong alkali that effectively breaks down the protein structure of the hair, making it easier to straighten. This substance penetrates the hair shaft and alters the disulfide bonds within the hair's keratin structure. By relaxing these bonds, sodium hydroxide allows for smoother, straighter hair.

Other ingredients mentioned, like calcium carbonate, are not typically associated with the primary function of hair relaxers. Calcium carbonate is often used in other hair products, such as shampoos or conditioners, but it does not serve the same purpose as sodium hydroxide in altering hair texture. Similarly, PVP/VA copolymer is a film-forming agent that helps in styling but doesn't affect the chemical structure of hair; it is used in products for hold and finish, rather than for a relaxing effect. Dimethicone is a silicone-based ingredient that provides conditioning and shine without changing the hair's structure, and thus, it also does not contribute to the relaxing process. Therefore, sodium hydroxide stands out as the main and functional ingredient in hair relaxers.