The pH level of your shampoo can have a big impact on the health of your hair. For shampoo, the best pH range is between 5.5 and 6.5. This range is the same as the pH range of a healthy scalp, which helps to maintain the natural balance of the scalp and hair, and prevent dryness, breakage, and other damage. The Iles Formula pH levels are: Iles Formula Haute Performance Shampoo: pH 5.5 - 6.5  Iles Formula Haute Performance Conditioner: pH 4.0 - 5.0  Iles Formula Finishing Serum Haute Performance: pH 4.0 - 5.0