What is the recommended pH level range for most hair shampoos?

The recommended pH level range for most hair shampoos is between 4.5 to 5.5. This pH range is slightly acidic, which is important for maintaining the health of the hair and scalp. Hair is naturally slightly acidic due to its composition, and using shampoos within this range helps to preserve the hair's cuticle layer, reduce frizz, and enhance shine. An appropriately acidic pH also helps to prevent the growth of harmful bacteria and fungi on the scalp, contributing to overall scalp health.

Using shampoos with a pH that is significantly outside of this range can lead to problems. For example, a pH that is too alkaline (like the higher values in the options provided) can strip the hair of its natural oils, leading to dryness, brittleness, and increased damage. Conversely, excessively low pH levels could create overly tight cuticles, making hair prone to tangling and breaking. Therefore, a pH level of 4.5 to 5.5 is ideal for maintaining the integrity and health of hair.