The aging of the human body is most likely to be reflected in the skin, and the culprit of skin aging is not natural aging, but caused by the more terrible photoaging. In the daily skin care routine, sun protection occupies arguably the most important position, sun protection is not all because of fear of tanning, but more importantly to prevent photoaging! In recent years, the incidence of various types of skin diseases induced by sunlight and ultraviolet rays has been increasing exponentially. Such as: sun spots, photosensitive dermatitis, chronic actinic dermatitis, dermal porphyrias, solar keratosis, malignant melanoma, etc. Skin aging is caused by both internal and external factors: 1) internal aging, also known as natural aging, is determined by individual genetic factors; 2) external aging is mainly caused by photoaging. Ultraviolet light is the most important factor, so external aging is generally defined as photoaging. In addition, smoking, haze, exhaust and pollution can accelerate the aging of skin. What is photoaging of the skin? After the age of 30, our face starts to show many problems such as pigmentation abnormalities (age spots, sun freckles, etc.), sagging skin, fine wrinkles, facial redness, enlarged pores, and dull skin color. This means that these changes in our face are not really aging in the true sense, which is called photoaging in dermatology. This means that light causes premature aging changes in the skin. The external aging of the skin is photoaging, which is mainly caused by ultraviolet radiation. It is characterized by roughness, thickening, laxity, deep and coarse wrinkles, excessive local pigmentation or capillary dilation, and possibly even various benign or malignant tumors. UVA is the main spectrum of skin tanning, its photochemical effect and photobiological effect is not as obvious as UVB, but the UVA in sunlight is more effective than UVB. UVA is the main spectrum of skin tanning, its photochemical effect and photobiological effect is not as obvious as UVB, but the dose of UVA in sunlight is many times higher than UVB, and the penetrating ability is strong, penetrating the deeper layers of the skin, so UVA also has an important impact in causing skin photoaging. 2. Internal factors: ①Physiological factors: The pathogenic effects of skin photoaging begin to accumulate from the time of receiving sunlight exposure, so attention should be paid to the protection of sunlight damage from infancy. In addition, as we grow older, the skin structure also changes accordingly, such as the integrity of epidermal stratum corneum, hydration and lipidation, epidermal thickness, color and the content of light-absorbing substances in the skin, etc. These factors can affect the reflection, scattering, absorption and penetration of ultraviolet rays in sunlight, thus affecting the development of skin photoaging. The color of skin is mainly determined by melanosomes in the epidermis, and melanosomes have good absorption of various wavelengths of ultraviolet and even visible and infrared light, therefore, melanosomes in the epidermis are the natural barrier to defend the dermal tissue from ultraviolet radiation damage. ②Pathological factors: A variety of skin diseases and pathological states can make the body more sensitive to UV radiation, and the clinical manifestations of mainly photodamage. ③Other: The above two aspects are the main causes of skin photoaging problems, in addition to occupation, geographical latitude and altitude, etc., which can also cause photoaging of skin for each individual. Solutions for skin photoaging: Currently, laser/light-based non-surgical methods are becoming the preferred treatment for many candidates and doctors to improve skin aging problems. 1. Exfoliative laser treatment Exfoliative lasers mainly include carbon dioxide (CO2) laser with a wavelength of 10600nm and erbium yttrium aluminum garnet (Er: YAG)) laser with a wavelength of 2940nm. Although the efficacy of full resurfacing lasers is remarkable, large area peels tend to form persistent erythema, skin sensitivity, scarring, and especially hyperpigmentation, so it is difficult to be widely performed in the Asian population. 2.Non-exfoliative laser/light treatment Non-exfoliative laser/light mainly includes pulsed intense light (500-1200nm), Nd:YAG laser (Q-switched 1064nm, long pulse width 1064nm, 1320nm), semiconductor laser (1450nm), Erbium:glass laser (1540nm), pulsed dye laser (585nm, 595nm), KTP laser (wavelength 532nm), radio frequency, infrared technology, focused ultrasound, etc. The principle of action is selective photothermal action: after the laser/photon acts on different target chromophores (melanin vesicles, hemoglobin, water), heat is generated, which stimulates the function of fibroblasts and synthesizes more collagen, elastin, hyaluronic acid, thus achieving the effect of wrinkle removal and skin tightening. 3.Fractional laser Fractional laser can be divided into ablative fractional laser and non-ablative fractional laser. The former mainly includes: CO2 fractional laser, Er pixel laser, Er:YAG super platform, RF fractional, ion beam laser, RF microneedle, etc. The characteristics are: the epidermis and superficial dermis are vaporized and coagulated at the same time, forming a fractional scab after surgery, which peels off in 3-7 days. The latter are mainly available: 1060nm, 1320nm, 1450nm, 1550nm lasers. Since the absorption peak of water molecules is deviated, the laser does not produce vaporization and exfoliation when it acts on the tissue. The energy penetrates into the dermis and stimulates skin renewal through photothermal action. The fractional laser retains the high performance of traditional ablative lasers while reducing side effects, and the post-operative recovery period is greatly reduced, if not completely absent, making it another milestone advancement in photoaging treatment.