The Protective Acid Mantle

Due to the presence of weak acidic components, the aqueous portion of the hydrolipid film forms the protective acid mantle, which fulfils three important skin functions:

• 1. Supports the formation and maturation of epidermal lipids, which helps maintain the barrier function
• 2. Indirectly protects from invasion of microbial pathogens
• 3. Directly protects against alkaline noxae

The protective acid mantle contains:

• Lactic Acid and various amino acids from sweat
• Free fatty acids from sebum
• Amino acids and pyrrolidine carboxylic acid from the cornification process

The physiological pH of healthy skin has an average value lying between 5.4 and 5.9 (In the armpits, anal folds and genitals, the pH is approximately 6.5). Within this pH range, the skin is populated by normal skin flora. Pathogenic microogranisms are hindered from spreading. The acidic pH of the horny layer plays an essential role in the formation and structure of epidermal lipids and with them, the permeability barrier. An acidic environment is important for:

• Activation of the enzymes responsible for the syntheses of important epidermal lipids
• Formation of the bilayer lipid membrane
• Restoration of the horny layer following mechanical or chemical damage