One of my natural friends wrote to ask me if it was recommendable to use a ph-balanced shampoo on her hair. Following is my reply to her after doing some researches.
Ph is potential hydrogen and varies from 0 (most acidic) to 14 (most basic or alkaline). A ph-balanced shampoo has a ph of 7, the middle of the scale, meaning that it is balanced to the acidic and alkaline levels.
A ph-balanced shampoo is good for your hair for many reasons. It keeps the hair cuticles closed, protecting the inner shaft from toxins. Moisture is locked in, which keeps hair flexible and prevent damages like split ends. If you permanently color your hair, it seals in the color and keeps it looking vibrant for a longer period. It will not strip natural oils from your scalp but will keep it clean.
Ph-balanced shampoo may be a misnomer. With the above being said, referring to a shampoo as pH-balanced may not be entirely accurate. A shampoo that claims to be pH-balanced should be formulated to be slightly acidic, because the pH of healthy hair is ideally 4.5 to 5.5, which makes it a little on the acidic side. A shampoo may contain citric acid to help lower the pH.
As shampoo mixes with the water in your shower or bath, or the dirt in your hair, it loses its acidity. Most shampoos contain a buffer that releases acidifying hydrogen ions when the acidity becomes too low, and absorbs them when the acidity level is too high. Sodium citrate is a common buffering agent used in shampoo.
The goal is to consistently maintain a slight acidity, because a shampoo that is slightly alkaline, or basic, will damage the hair shaft, causing the hair to become dull and rough.
Source: Charlotte LoBuono, Daily Glow
Herbal Essences is an example of ph-balanced shampoo.