What defines a pH-balanced shampoo?

A pH-balanced shampoo is defined as one that is formulated to have a pH level that aligns closely with that of human hair and skin, typically around 4.5 to 5.5. This balance is crucial because it helps to maintain the natural acidity of the hair and scalp, which can protect against environmental damage and excessive dryness.

Using a shampoo that is pH-balanced is important for preserving the hair's cuticle layer, aiding in moisture retention, and preventing frizz. A pH level higher than this range can potentially lead to raised cuticles, causing damage and making hair more susceptible to issues like breakage and color fading. Therefore, the characteristic that defines a pH-balanced shampoo aligns it with the natural pH of skin and hair, providing the gentleness and effectiveness needed for hair care.

In contrast, the other options do not accurately define a pH-balanced shampoo. Increasing hair volume involves volumizing ingredients, while a pH of 7 or higher would be alkaline and could damage hair. Harsh chemicals may strip the hair of its natural oils and disrupt its pH balance, thus they're not suitable for maintaining healthy hair.