The pH level of soap is 10. Because soaps are basic, they can effectively clean off the acid mantle of the skin and remove dirt.
The pH scale measures the concentration of hydrogen ions in a chemical or substance and classifies it as acidic or basic, also called alkaline. A pH level of 7 is neutral, such as water, while a pH level below 7 is acidic and above 7 is basic. With a pH level of 10, soap is an alkaline or base.
The acid mantle on the skin serves as a protective layer, but it also builds up dirt, oils and germs. The alkalinity of soap breaks down this acidity through a neutralization reaction which cleanses the skin.