First of all, we should know that the human skin cuticle contains 10% - 20% water. When the water is sufficient, the skin will appear moist and elastic. When the water in the cuticle is less than 10%, the skin will appear dry, wrinkled and even desquamated. In moisturizing cosmetics, there are four kinds of raw materials that can moisturize: oil components, hygroscopic small molecule compounds, hydrophilic large molecule compounds and restorative components, oil components: such as Vaseline, olive oil, almond oil, etc. these raw materials can form oil film on the skin surface after use, which is equivalent to a layer of fresh-keeping film on the skin, which can slow down the cuticle layer The function of water loss is to keep the water content of cuticle. Hygroscopic small molecule compound, its moisturizing ingredients are mostly small molecules, polyols, acids and salts, etc., they have water absorption, can absorb water from the surrounding environment, and then improve the water content of the skin cuticle, common are glycerin, butanediol, sodium pyrrolidone carboxylate, lactic acid and its salts, etc. Our commonly used moisturizing cream moisturizing cream formula generally contains both hygroscopic small molecules and oils that can form oil film. Hydrophilic macromolecular compounds,