pH is a numerical range from 0-14 and measures whether a liquid is acidic (0-6.9), neutral (7) or alkaline (7.1-14). The natural pH of our scalp ranges from 4.5 - 5.5, found to be within the acidic range. This pH is created naturally by the secretion of oil (sebum) and sweat. Using products outside the natural pH range can have a negative impact on the scalp and hair.