California Cosmetology Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

The main ingredient in lye-based relaxers is sodium hydroxide. This compound is a strong alkaline agent that works by breaking down the hair's protein structure, effectively relaxing the curls or waves in the hair. Sodium hydroxide is well-known in the beauty industry for its effectiveness in achieving straight hair and is the most commonly used ingredient in traditional perm and relaxer formulations.

Understanding the role of sodium hydroxide highlights its significance in chemical processes within hair treatments. It is crucial for cosmetologists to comprehend the chemical interactions that occur during the relaxing process, as this knowledge aids in appropriate usage, application techniques, and ensuring the health and safety of clients' hair and scalp.

Other ingredients listed, such as calcium hydroxide, potassium hydroxide, and magnesium hydroxide, may also be found in various hair products but serve different purposes or are used in non-lye formulations. This is why sodium hydroxide is distinctly identified as the primary component in lye-based relaxers.