The acid mantle, the combination of sebum (oil) and perspiration on the skin's surface, protects the skin and renders it less vulnerable to dehydration, damage and attack by environmental factors such as sun and wind. The acid mantle inhibits foreign bacteria flora and fungi growth (pathogens) through its alkali-neutralizing capability. Thus it is the key to true skin health and beauty. This very fine film, with a slightly acidic pH, rests on the skin's surface, acting as a barrier to diseases and the elements. It becomes compromised when the skin is washed or exposed to elements. The body works hard to keep this barrier intact, but once it is damaged, it can take up to 14 hours to restore. By then it is usually under another assault and the skin begins to appear dry, wrinkled and aged.