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

Sodium hydroxide is a key ingredient commonly used in hair straightening treatments, especially in the context of relaxers. This chemical acts as an alkaline substance that helps to break down the disulfide bonds in the hair's structure. By altering these bonds, sodium hydroxide effectively changes the natural curl pattern of the hair, allowing it to be straightened and styled as desired.

The use of sodium hydroxide is particularly noted in products labeled as "lye relaxers." Its high pH level not only aids in the straightening process but also can lead to significant changes in the hair's texture and manageability. Because of its potency, users and professionals must exercise caution to avoid excessive damage to the hair and scalp.

In contrast, other options listed serve different purposes in the beauty and hair care industry. For instance, ammonium thioglycolate is recognized for its use in perms rather than straightening. Cationic surfactants are typically incorporated in conditioning products for their ability to soften and detangle hair. Glyceryl monostearate acts mainly as an emulsifier in various cosmetic formulations, not directly involved in straightening hair. Understanding the specific role and function of each chemical is crucial for effective and safe hair treatments.