Ace the Virginia Cosmetology Test 2025 – Style Your Skills and Shine Bright!

Sodium hydroxide is commonly used in hair relaxing treatments due to its strong alkalinity. This potent chemical breaks down the hair's disulfide bonds, which are responsible for the hair's natural curl or wave pattern. When applied to the hair, sodium hydroxide allows the hair's structure to be altered, thereby making it straighter. This process is typically referred to as "lye relaxers," which can provide effective results for many hair types, particularly those with tightly coiled or curly hair.

In contrast, calcium hydroxide is also used in some hair relaxers but typically in combination with other chemicals. Ammonium thioglycolate, while used in perm solutions and some relaxers, operates differently and is not the primary chemical used in traditional hair relaxing. Glycolic acid is primarily used in other cosmetic applications such as skin exfoliation and is not relevant to hair relaxing treatments. Thus, sodium hydroxide stands out as the most common and effective agent in straightening curly or wavy hair.