What is a fundamental ingredient in most relaxing solutions?

Sodium hydroxide is a fundamental ingredient in most relaxing solutions because it acts as a strong alkaline agent that breaks the disulfide bonds in the hair. This process is essential for relaxing and straightening curly or wavy hair, allowing it to achieve a smoother texture. Sodium hydroxide opens the hair cuticle, enabling the chemicals to penetrate the hair shaft efficiently. Its pH level, which is typically much higher than that of hair, provides the necessary conditions for the hair to become malleable during the relaxing process.

In contrast, ammonia is generally used in hair coloring products as a pH adjuster rather than as a primary ingredient in relaxers, while hydrogen peroxide serves as a bleaching agent and not directly related to hair relaxing processes. Alcohol might be included in some hair care products for its drying properties or as a solvent but does not play a role in the relaxation of hair. Thus, sodium hydroxide is essential for the chemical processes involved in effectively relaxing the hair.