Everything grows by the sun, and so do humans. While people enjoy the bounty of the sun, they can also suffer from skin diseases due to exposure to ultraviolet light. How does sunlight damage the body? Sunlight includes ultraviolet light, visible light and infrared light, among which ultraviolet light is more harmful to the human body. UV radiation is divided into short-wave UV (wavelength 180-290nm), medium-wave UV (wavelength 290-320nm), and long-wave UV (wavelength 320-400nm). Different wavelengths of ultraviolet light can be absorbed by different tissues in various layers of the skin. The longer the wavelength, the stronger the penetrating ability. Medium-wave UV is mainly absorbed by the epidermis and damages the epidermis; long-wave UV can reach the upper dermis and can act on blood vessels and other tissues. Sunlight damage to the body through phototoxic and metabolic two ways to damage the body. 1, phototoxic reaction is a non-immune reaction, anyone can suffer. Local exposure to strong sunlight, a short period of time will produce erythema, edema, blisters and other skin lesions; long-term repeated exposure to strong sunlight medium-wave ultraviolet radiation, can lead to skin wrinkling, relaxation, surface dryness, roughness or atrophy, pigmentation or hypopigmentation. 2, photopathogenic reaction is an immune reaction. As long as there is a small amount of photosensitive substances in the human body, the reaction will occur by ultraviolet radiation, the pathogenic spectrum is mainly long-wave ultraviolet light, and can even migrate to visible light with a wavelength of 400nm or more, and can also be medium-wave ultraviolet light. The clinical characteristics of phototoxic reactions are that they only occur in a few allergic people, and, when first exposed to photosensitive substances and radiated by sunlight, inflammatory reactions do not occur within a short time, but there is a certain sensitization period, usually taking 1-2 days or more for the reaction to occur. What kind of skin damage is caused by phototoxic reactions? The skin damage caused by phototoxic reactions is called sunburn, which is an acute localized erythema and edematous skin inflammation caused by intense sunlight exposure. How to prevent sunburn? 1, to reduce the time of exposure to strong sunlight, often participate in outdoor activities, in order to enhance the skin’s ability to tolerate the sun. For allergic people, the following things should be noted. 2, reduce the time to go out in strong light: the strongest light of the day from 10:00 a.m. to 2:00 p.m., this time should be reduced to go out, if necessary, need to take shade such as playing umbrella, wear long-sleeved clothes, etc., and must use sunscreen. 3, drug prevention: oral niacinamide, beta-carotene, B vitamins, etc.. When the dermatitis attack, oral hydroxychloroquine, reaction stop (pregnant women should not be used), etc.. The sun spots can be used as furnace glycolic lotion or ice water wet compress; chronic solar dermatitis can be moderate amount of topical hormone ointment and cream. Recent studies have concluded that Bute has a role in preventing sun exposure and reducing sun damage, and can be used topically for treatment. Most oral antihistamines can reduce the sensitizing effect of ultraviolet light on the skin.