New Hampshire Cosmetology Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

The ideal pH level for shampoos designed for color-treated hair is generally in the range of 4.5 to 5.5. This pH balance is crucial because it is slightly acidic, which helps to maintain the hair's natural protective barrier, known as the cuticle. When the pH is within this range, it can effectively clean the hair without causing excessive swelling or damage to the cuticles, which can result in color fading or loss of vibrancy.

Shampoos that are too alkaline (such as those with a pH level above 7.0) can raise the cuticle, leading to an increased risk of moisture loss and color bleeding. This is particularly problematic for color-treated hair, as the dyes can leach out more easily when the cuticle is lifted. Conversely, shampoos with a pH that is too low (like those in the range of 3.0 to 4.0) can be overly harsh, potentially causing irritation to the scalp and further compromising the integrity of the hair.

Maintaining a pH level conducive to both cleaning and protecting hair color is essential for keeping color-treated hair looking vibrant and healthy.