What key ingredient does a neutralizer contain?

A neutralizer is an essential component in the chemical relaxing or perming process, as it is responsible for restoring the disulfide bonds in the hair, which were broken during the application of a waving or relaxing solution. The key ingredient found in most neutralizers is hydrogen peroxide.

Hydrogen peroxide acts as an oxidizing agent, facilitating the reformation of these bonds and stabilizing the hair structure after it has been altered by the chemical treatment. By doing so, it ensures that the newly styled shape or texture is set and lasts.

The other ingredients listed, such as ammonium thioglycolate, sodium hydroxide, and calcium hydroxide, serve different functions. Ammonium thioglycolate is primarily used as a reducing agent in perm solutions, while sodium hydroxide is a strong alkaline ingredient that is usually found in relaxers. Calcium hydroxide is sometimes used in certain chemical treatments but does not serve as a neutralizing agent. Thus, hydrogen peroxide is specifically recognized for its role in the neutralization process, making it the right choice for this question.