Acid mantle

The acid mantle is a very fine, slightly acidic film on the surface of human skin acting as a barrier to bacteria, viruses and other potential contaminants that might penetrate the skin. It is secreted by sebaceous glands. The pH of the skin is between 4.5 and 6.2, slightly acidic. Since blood is slightly alkaline (7.4), pathogenic bacteria that become adapted to the pH of the skin and are able to reach internal tissues will encounter an environment to which they are less well adapted. This combination of acidic exterior and alkaline interior is one of the body's non-specific host defenses against bacterial pathogens.