Our skin has a special feature: its surface is slightly acidic. On average the pH value of the skin is 5.5. The slightly acidic pH value of the surface of the skin wards off pathogens that cause disease. The balance of the ecosystem of the surface of our skin promotes harmless micro-organisms well-adapted to humans which are found in thousands on every square centimetre of the skin. Harmful bacteria and fungi do not tolerate the acidic pH value and are displaced by normal micro-organisms. In addition, the acidic pH value also stabilizes the skin’s function as a barrier. It ensures that lost fat in the horny layer is replenished quickly through reproduction. Another effect of the pH value of 5.5 is that the lipids in the horny layer retain their labyrinthine structure. This prevents water loss from the inside and penetration of pollutants or irritants from the outside. Thus the skin’s acid mantle performs an important protective function.
Changes in the pH value of the skin weaken the protective function of the acid mantle. This promotes skin infection, dehydration, skin irritations and allergies.
The pH value shows whether a liquid is acidic, neutral or a base (alkaline). The pH scale ranges from 0 to 14. The neutal point is 7. Values over this point denote bases, value under this point acids. The further the value is away from 7, the stronger is the acid or base.
Not only skin contact with strong acids or bases but also daily skin care damage the protective acid mantle when soap or other care products whose pH value does not correspond to the skin’s natural pH value of 5.5 are used. This is true for most so-called preparations with skin neutral pH.