Today we’re going to talk to you about moisturizing. Why do we need to moisturize our skin? I’m afraid many of us don’t have a clear answer to this question. Our skin is directly exposed to the atmosphere and is always susceptible to external temperature, wind and cold, and dryness. When the skin is to maintain normal physiological functions, it needs a stable internal environment, and thus maintaining a certain level of moistness is the most basic condition. Moisturizing cosmetics are the most commonly used skin care products to maintain skin moisture content by simulating the skin’s natural moisturizing system. Now that we understand the importance of moisturizing, let’s take a look at how the moisturizing cosmetics we normally use work. Different moisturizing ingredients have different moisturizing mechanisms within the skin. In a cosmetic formula, moisturizing ingredients with different mechanisms of action are often compounded together to work together. In practice, it is necessary to choose products with different combinations of ingredients according to the physiological and pathological mechanisms of the skin in order to target the moisturizing effect of cosmetics better. Substances that can absorb water from the deeper layers of the skin and the external environment and preserve it in the stratum corneum are what we call hygroscopic agents. The most common of them are glycerin, sorbitol, honey, urea, propylene glycol, etc. Moisture absorbers tend to absorb water from the external environment when the relative humidity around the skin reaches at least 70%. So in general, moisture absorbers absorb water mainly from the dermis. In a very low relative humidity, cold, dry, windy environment, the moisture absorbed from the deeper layers of the skin will also evaporate through the epidermis, making the skin drier, so it is not advisable to use moisture absorbers alone in a dry environment, and should be used in conjunction with emollients and sealants. Sealants are a class of substances that can form a thin hydrophobic oil film on the skin surface to prevent or delay the evaporation and loss of water. They are usually relatively oily and are represented by substances such as petroleum jelly, but also include highly viscous ash oils, various triglycerides, and various ester oils. Emollients fill in the cracks between the keratinocytes of dry skin to make the surface texture smoother and are classified as protective emollients (e.g. diisopropyldioleic acid), depigmenting emollients (e.g. jojoba oil, castor oil), astringent emollients (e.g. dimethicone) and dry emollients (e.g. isopropyl palmitate). There is also a large class of natural biological macromolecules with hydrophilic properties, which can combine the free state of water in the three-dimensional mesh structure it forms, so that the free water is not easy to evaporate and dissipate, such as hyaluronic acid, chondroitin sulfate, collagen, elastin and so on.