Final answer:
A neutralizing shampoo's purpose is to correct the pH balance of hair after using alkaline cleaning agents, bringing it back to its ideal slight acidity.
Step-by-step explanation:
A neutralizing shampoo is designed to re-balance the pH level of your hair by neutralizing any alkali and unwanted residues in the hair. The sulfate ingredient in most shampoos acts as a surfactant, which helps remove oil and grease, but the process can sometimes leave hair with a high pH due to residues from cleaning agents. A neutralizing shampoo corrects this by bringing the hair back to a slight acidity, usually with a pH less than 7, which is ideal for hair health.