pH value is the expression of the acid-base degree. It is expressed as a number from 0 to 14. The number 7 is neutral, the number above 7 is alkaline, and the number below 7 is acidic. The pH value of hair for its best conditions is between 5.5 and 6.5.

Hair itself does not have a pH value. The pH value of the hair refers to the pH of the sebum secreted by the scalp.

When hair is in contact with an alkaline epidermis, it will open and split, and hair will become rough and porous. When the acidic epidermal layer is closed, the hair texture feels good and shiny. Note that due to strong cleaning functions, supermarket shampoo is generally a weak alkaline, which can easily damage the weak acidic environment of the scalp in the long term, causing bacteria to multiply, as weak acidity inhibits the growth of bacteria.