New York State Cosmetology Practice Exam 2025 - Free Cosmetology Practice Questions and Study Guide

The primary ingredient in most hair relaxers is sodium hydroxide. This chemical, commonly referred to as lye, is known for its strong alkaline properties, which help to break the disulfide bonds in the hair's keratin structure. When these bonds are broken, the natural curl or wave pattern of the hair is loosened, allowing the hair to be straightened.

Sodium hydroxide is particularly effective for achieving permanent hair straightening results. It can penetrate the hair shaft, making it suitable for coarse or thick hair types that require a more robust treatment to achieve desired straightness.

Other ingredients like ammonium thioglycolate are often found in perm solutions but are not usually the primary agents in relaxers. Glycerin functions as a moisturizer and is not a relaxing agent, while cocamidopropyl betaine is a surfactant used in formulations for its mildness and foaming properties. Therefore, understanding the role of sodium hydroxide is essential for anyone working in cosmetology, as it plays a critical role in the effectiveness of hair relaxing treatments.