On the pH scale, a value of 7 is considered:

On the pH scale (which runs from 0 to 14), a value of 7 is neutral — neither acidic nor alkaline. Values below 7 are acidic (with 0 being the most acidic), and values above 7 are alkaline/basic (with 14 being the most alkaline). Pure water is neutral at pH 7. Healthy skin and hair are slightly acidic (around 4.5–5.5). Understanding the pH scale is essential in cosmetology because many products and chemical services depend on raising or lowering pH to achieve their effects.