The skin not only plays a beautifying and decorating function for human individuals, but also is the largest organ of the human body. In addition to the common biochemical metabolic process with other organs, the skin also has its own metabolic characteristics and specific physiological functions. 1, the skin’s protective and absorptive role The protective role is mainly reflected in: on the one hand, to prevent the loss of water, electrolytes and other substances in the body, on the other hand, to prevent the invasion of harmful or unwanted substances from the outside world, both of which are extremely important for maintaining the stability of the internal environment of the body. The absorption pathways of the skin are mainly through the cells of the epidermal stratum corneum, the interstitial cells of the stratum corneum and the hair follicles, and through the sebaceous glands or sweat ducts; the stratum corneum cell pathway is the main one. If there is damage to the stratum corneum, various solids, liquids and trace gases in contact with the skin may be absorbed by the skin. 2, skin secretion and excretion role mainly through the sweat and sebaceous glands for sweat secretion and sebum excretion. Sweat is similar to some of the excretory products of the kidney, and mixed with sebum to form a milky lipid film, which protects the skin, and its acidity can inhibit the growth of bacteria. The acidity of the film inhibits bacterial growth. Sweating dissipates heat and cools the body. Sebum plays a role in moisturizing hair, preventing skin dryness and cracking, inhibiting the reproduction of certain bacteria on the skin surface and acne. 3, the skin’s thermoregulation and sensory role. The thermoregulatory center regulates the contraction and dilation of skin blood vessels through sympathetic nerves, changing the blood flow in the skin and the diffusion of heat, thus regulating body temperature. The diffusion of heat from the body surface is mainly carried out by thermal radiation from the skin surface, evaporation of sweat, convection of air around the skin and heat conduction. The skin has a variety of sensory nerve endings that can produce single sensations such as touch, pressure, cold, and heat, as well as conforming sensations such as dry, wet, smooth, rough, and soft.