Usefulness of Skin Hydration for Skin Care and Development of Cosmetics

Maintaining suitable skin hydration is very effective for preventing dry skin. This is the most basic and important function of cosmetics. Various types of emollients and humectants are used in skincare products to prevent water loss from the skin and retain water. In the stratum corneum, the importance of natural moisturizing factor (NMF), sebum and intercellular lipids has been demonstrated. From a dermatological approach, we have already reconstructed an analogy of the skin hydration mechanism. For dry skin, we have demonstrated the usefulness of “moisture balance;” that is, to supply equivalent substances of water, humectants and oils in cosmetics. It is also important to develop cosmetics from a pharmacological approach. This is very helpful in the development of new, more effective components for cosmetics. Recently we have clarified the important role of epidermal protease activity in dry skin. Inhibition of its activity accelerates intercellular repair response. We have developed trans-4-aminomethyl cyclohexane carboxylic acid (t-AMCHA), which has an anti-plasmin (a epidermal protease) activity and can cure dry skin. This article reviews the skin hydration mechanism and development of skin care cosmetics utilizing dermatological and pharmacological approaches.