Specific amounts of water and lipids on the skin surface determine the composition of the hydrolipidic film of the skin. Its slightly acidic pH value is a major protective factor for the skin, buffering acids and alkaline products that get in contact, as well as providing an environment favourable to our natural microbiome, while at the same time restricting the growth of pathogenic microbes.
The term acid mantle describing this aspect was first used in 1928 by Heinrich Schade and Alfred Marcchioni. Based on further technical developments and continuous research in dermatology and skin physiology, biochemistry, immunology and genetics, today, we know that the acidic skin pH value is involved in many more functions.
The pH value of the skin is influenced by different endogenic factors such as genetic disposition, age, gender, health, melanin content and sebum secretion. It is easily impacted by external influences, especially cleansing and care products, but also by sweat and moisture.
Newborn babies show a more or less neutral skin surface pH. In the first four weeks after birth, this value slowly decreases[2, 3, 4], reaching an acidic level that will only change again in older age.
In elderly skin, after 60-70 years of age, an increased pH value can be measured again. At the same time, researchers have observed a decreasing buffering capacity of the skin for these elderly patients[5, 6].