With the improvement of people’s living standard and the increase of life expectancy, how to age healthily and beautifully has become a topic of concern. As the outermost layer of the human body, the aging of the skin is the most important indicator to evaluate the aging of the human body, so how to prevent, delay and reverse the aging of the skin is becoming a hot spot for research in dermatology, cosmetic science and other disciplines. The external causes of skin aging are more important. As the largest organ of the human body, the skin, like other internal organs, goes through the natural aging process. Natural aging is caused by genetic factors and irresistible factors (such as gravity, changes in endocrine and immune functions with the aging of the body, etc.), which mainly lead to the decline of various skin functions. Natural aging of the skin is characterized by pale skin, mild atrophy, and fine wrinkles. Natural aging has less impact on the appearance of the skin. As the outermost layer of the human body, the skin is in direct contact with the external environment, so it also undergoes a unique exogenous aging process. Exogenous aging is caused by ultraviolet light, infrared light, wind exposure, dryness, smoking, and exposure to chemicals. Beauty-related skin changes, such as skin roughness, sagging, elasticity loss, coarse and deep wrinkles, pigmentation and hyperpigmentation, hypopigmentation and capillary dilation, are mainly caused by skin photoaging. In addition, a variety of benign lesions, pre-cancerous lesions and malignant skin neoplasms are also closely related to skin photoaging. In conclusion, the degree of skin aging is the result of the superposition of natural aging and photoaging, and 90% of lesions affecting skin aesthetics in exposed areas such as face and neck are caused by photoaging. Therefore, effective prevention, intervention and repair of skin photoaging can significantly slow down the process of skin aging and maintain the health and beauty of the skin. UV rays have the greatest impact on skin aging It is currently believed that UV rays are the most important environmental factor that causes skin photoaging, and therefore, comprehensive photoprotection measures are an important means of preventing and repairing photoaging. Measures that can be taken include minimizing going outside when the light is strong from 10 a.m. to 4 p.m. or trying to find shade, using a wide-brimmed hat, using UV-protective sunglasses and using broad-spectrum sunscreen. Some people will slow down the skin aging methods summarized as three “C”, that is, summer out wearing a hat (cap), wear long-sleeved clothes (clothes), coated with sunscreen (cream). These methods can effectively prevent excessive exposure of the skin to UV rays. Consistent use of sunscreen is particularly important for the prevention and repair of photoaging. Sunscreens have been shown to not only prevent acute damage from the sun, but also to reduce the degree of photoaging. Recent studies have shown that regular use of broad-spectrum, highly effective sunscreens can prevent photoaging at the cellular level, so early photoprotective intervention is necessary. The ideal sunscreen requires protection against UVA and UVB, photostability, and good cosmetic effects. Skin aging is related to free radicals There are at least 300 theories explaining aging from ancient times to the present, and eight more recent and well-established aging theories. Studies have shown that both natural skin aging and photoaging can lead to excessive production of free radicals, causing cellular biofilm damage, mitochondrial damage and glycoprotein glycation, thus further aggravating skin aging. Therefore, internal or external use of antioxidants has become an important treatment for skin aging prevention. Antioxidants added to cosmetics include topical preparations of vitamin C and vitamin E, alpha-hydroxy acids and a variety of plant extracts such as green tea, ginger, ginkgo biloba, grape seed, olive oil, lycopene, carotene, strawberry, papaya, soybean, ginkgo biloba and coffee bean extracts all have antioxidant activity and can slow down skin aging to some extent. A group from the Department of Dermatology at the University of Michigan has found, after years of research, that topical retinoic acid preparations can significantly improve skin sagging, wrinkles, pigmentation spots and other signs of photoaging. Retinoic acid is the only well-studied drug that can fight skin aging at the molecular level. Currently, retinoic acid and its derivatives are important ingredients in anti-aging cosmetics. Bad habits that cause premature appearance of wrinkles Squinting, supporting chin or cheeks with hands, lying on the side or prone, washing face with hot water, fluctuating weight, unbalanced diet, lack of sleep, smoking, drinking drinks through a straw frequently. Medical aesthetic treatments that can rejuvenate the skin Medication: use of botulinum toxin, fruit acid treatment, use of retinoids, dermal fillers. Cosmetic laser treatments: use of intense pulsed light, 1064nm laser, 755nm laser, pixel laser, etc.