Depending on the brand, shampoo is slightly acidic to neutral, with pH levels ranging from 4.8 to 7. With pH levels ranging from 2.8 to 7, hair conditioners tend to be much more acidic.
The pH (or potential/power of hydrogen scale) indicates whether a substance is acidic or basic. The range of the scale is from 0 to 14, with 7 representing neutrality. Substances that are acidic do not attract as much hydrogen, therefore their pH is less than 7. On the pH scale, compounds with a pH greater than 7 attract more hydrogen, as they have a higher hydrogen affinity. The pH of human hair and skin is often between 4.5 and 5.5.