The long-term use of soap does not affect the pH-maintenance mechanism of human skin.

Abstract

The pH at the surface of healthy human skin is around 5. Cleansing the skin with soap increases the pH of the skin, which then returns to a more acidic pH within a few hours. However, the effects of skin cleansing with soap over a long time on the pH regulatory system is still unclear. We compared the pH of the skin between users of a soap-based cleanser and of a mild-acidic cleanser prior to and following the cleansing. This study had two groups of subjects, one group who had used a soap-based cleanser for more than 5 years and the other group who had used a mild-acidic cleanser for more than 5 years. The pH on the inner forearm of each subject was measured prior to and for 6 h after cleansing with a soap bar. There were no differences between the pH of the skin these two groups prior to cleansing, immediately after cleansing or in the pH recovery rate for 6 h. These results suggest that long-term continuous use of a soap-based cleanser does not affect the pH-maintaining mechanism of human skin.