IMMUNOLOGY

Detailed explanation-1: -The acidic pH of human skin surface, often termed the “acid mantle, ‘’ is a key component of healthy skin. Recent investigations measuring skin surface pH in healthy volunteers report an average pH between 4.1 and 5.8 [4].

Detailed explanation-2: -"The skin’s barrier is slightly acidic for a reason: to keep moisture in and bacteria out, Dr. Karcher says. “If your pH balance is off and it’s too alkaline, your skin is going to look flaky and red. If it’s too acidic, you’ll increase your chances of inflammatory skin conditions like eczema and acne.”

Detailed explanation-3: -A pH of 7 (that of pure water) is considered neutral. Anything below that is acidic and above it alkaline, so skin’s natural pH is mildly acidic. This mildly acidic pH is created by skin’s acid mantle, the water part of the hydrolipid film that protects the external layers of skin.

Detailed explanation-4: -Most bacteria are neutrophiles, meaning they grow optimally at a pH within one or two pH units of the neutral pH of 7, between 5 and 8 (see Figure 9.35). Most familiar bacteria, like Escherichia coli, staphylococci, and Salmonella spp. are neutrophiles and do not fare well in the acidic pH of the stomach.

Detailed explanation-5: -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. Sebum is secreted by the sebaceous gland and when mixed with sweat becomes the acid mantle.

Detailed explanation-6: -The acid mantle is characterized by a pH value of 4–6, as a result of amino acids, fatty acids, sebum secreted by the sebaceous gland, and lactate excreted from sweat. All of these compounds are acidic and when present together on the human skin, become a barrier that prevents bacterial colonization.