Lactic Acid, Lactic acid bacteria
Lactic acid, also known as 2-hydroxy propionic acid, is a part of the natural moisturizing system as well as the acid protective layer of the skin and thus regulates the physiological pH and bacterial colonization of the skin. Industrially, it is sugar-based or synthetically derived from Lactobacillus species.
In cosmetics, lactic acid acts against calluses and has a very mild peeling effect. The outer layer of the skin is thinner and more flexible after the use of lactic acid, which is desirable especially when caring for blemished skin, acne, psoriasis and cornification disorders. In addition, lactic acid is hydrating and pH-regulating and thus inhibits the growth of other microorganisms on the skin.
see. Heike Käser 2010 "Natural Cosmetic Raw Materials", Linz, Freya Verlag, 3rd Edition 2012