Missouri Board of Cosmetology Practice Exam

The primary ingredient in most chemical relaxers is sodium hydroxide. Sodium hydroxide acts as a strong alkaline substance that breaks the disulfide bonds in the hair's keratin structure. This process helps to straighten curly or textured hair by altering its natural structure.

Sodium hydroxide is often used in both professional salon relaxers and some over-the-counter products. It can achieve varying degrees of relaxation depending on the concentration and application technique, making it suitable for a range of hair types.

Other ingredients listed, such as calcium hydroxide and potassium hydroxide, are also alkaline agents used in some relaxers, but they are less common than sodium hydroxide. Ammonium thioglycolate, on the other hand, is primarily used in permanent waving and not typically in relaxers designed to straighten hair. Hence, sodium hydroxide stands out as the most prevalent and widely utilized ingredient in relaxers.