Ohio Cosmetology License Practice Exam

What is the primary ingredient in most hair relaxers?

1. Calcium hydroxide

2. Sodium hydroxide

3. Ammonium thioglycolate

4. Potassium hydroxide

The correct answer is: Sodium hydroxide

The primary ingredient in most hair relaxers is sodium hydroxide. This chemical, commonly known as lye, is highly effective for breaking down the disulfide bonds of curly or wavy hair. By doing so, it alters the hair's structure and allows it to be straightened. Sodium hydroxide relaxers are favored for their potency and the speed at which they work, making them a popular choice in many salons. Other ingredients, while also used in various types of hair treatments, serve different purposes. For example, calcium hydroxide is often combined with another agent to create a milder form of hair relaxer, but it is not as common as sodium hydroxide. Ammonium thioglycolate is typically used for perms and is not considered a relaxer since it works by creating curls rather than straightening hair. Potassium hydroxide functions similarly to sodium hydroxide, but it is less prevalent in hair relaxers. Overall, sodium hydroxide remains the predominant choice for effective and efficient hair relaxation.