Tennessee Cosmetology Practice Exam 2025 - Free Cosmetology Practice Questions and Study Guide

The main ingredient found in most hair relaxers is sodium hydroxide. This chemical compound acts as a strong alkali and helps to break down the disulfide bonds in the hair's protein structure, which is crucial in relaxing tightly curled or frizzy hair. When applied, sodium hydroxide alters the hair's natural structure, making it more manageable and straighter. Products containing this ingredient are effective for achieving straight hair but require careful application to prevent damage, as the high pH can lead to hair and scalp irritation if not used correctly.

Calcium hydroxide is also used in some relaxers, particularly in combination with sodium hydroxide, but it is less common and typically not the primary active ingredient. Amino acids play a role in hair health and are often found in conditioners or treatments but do not serve the same purpose in relaxing hair. Hydrogen peroxide is primarily used as a bleaching agent and in hair color services rather than as a straightening agent.