Our skin is slightly acidic in nature. According to the pH scale, the epidermis has a pH between 5.5 and 5.6.
The outermost layer of the epidermis is known as the acid mantle. It is a protective layer comprised of a combination of dead skin cells, oil, and perspiration. Perspiration consists of lactic acid which, in turn, gives our skin the slightly acidic value. It is important to note that microorganisms cannot live in an acidic environment. This is the reason why it is considered a protective barrier; germicidal invasion is denied. The acid mantle also seals moisture into the cells located in the epidermis, therefore, protecting the skin against dryness.