Soap that is pH-balanced is slightly acidic, making it similar to the pH level of human skin, which is about 5.5. The pH scale runs from 0 to 14, with seven being neutral. Less than 7 is acidic, while the higher end of the scale is basic.
The outer layer of skin is acidic to help keep it from drying out and to ward off microorganisms such as bacteria. Soaps that are pH-balanced do not interfere with this process. The pH of these cleansers is typically slightly higher than 5.5 in order to promote the removal of dirt and oil. However, many bar body soaps fall between 9 and 12 on the pH scale, as these remove acid and lead to dry skin.