What are neutralizers used for in hair treatments?

Neutralizers are essential in hair treatments, particularly in the perming process. They play a critical role in stopping the action of permanent wave solutions, which break down the hair's internal disulfide bonds to allow for reshaping. Once the desired curl or wave is achieved, applying a neutralizer serves to rebalance the hair's pH and rebuild these disulfide bonds, effectively locking the new shape in place. This step is crucial; without a neutralizer, the hair would revert to its natural state, and the intended style would not be maintained.

The other options do touch on aspects of hair treatment but do not pertain to the primary function of neutralizers. Adding shine, removing excess product, or enhancing color retention are not the main functions associated with neutralizers in the perming process. Thus, the focus on disulfide bonds and their reconstruction is what distinguishes the correct answer as the primary purpose of neutralizers in hair treatments.