Maryland Cosmetology State Practice Exam 2025 - Free Cosmetology Practice Questions and Study Guide

Sodium hydroxide is indeed recognized as a type of chemical used for hair relaxing, specifically in the application of relaxers. It serves as a strong alkali that breaks down the disulfide bonds in hair, allowing the hair to be straightened. This process alters the hair's structure, making it easier to manage and style for those with naturally curly or wavy hair. Sodium hydroxide is a key ingredient in lye relaxers, which are known for their effectiveness and potency in achieving smooth, relaxed hair.

In the context of hair treatments, the other chemicals listed serve different purposes. For instance, hydrogen peroxide is primarily used as a bleaching agent or in hair dyes rather than for relaxing hair. Ammonium thioglycolate, while also used in perming and softening treatments, is typically associated with the perming process rather than specifically hair relaxing. Alcohol is generally used in various cosmetic products for its antiseptic properties, but it does not function in the relaxing process of hair. Understanding the role of these chemicals clarifies why sodium hydroxide is the correct answer in this context.