Maine Cosmetologist Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

The primary ingredient in most hair relaxers is sodium hydroxide. This ingredient is known for its effectiveness in breaking down the protein structure of the hair, allowing it to be straightened. Sodium hydroxide is a highly alkaline substance, which raises the pH of the hair, enabling the cuticle to open and the hair's natural structure to be changed.

In many professional settings, sodium hydroxide is favored for its quick action and potency, making it a common choice among cosmetologists for clients with coarse or curly hair requiring significant texture change.

Though other ingredients such as calcium hydroxide, ammonium thioglycolate, and potassium hydroxide are also used in some relaxer formulations, sodium hydroxide remains the most widely used and recognized active ingredient for its strong relaxing effects. This high pH level allows for effective straightening, making it an essential component in the hair relaxing process.