With the advent of summer, with the outdoor UV rays raging, another sunscreen season has arrived, proper sunbathing is said to help health, in foreign countries are also prevalent in the “sunbathing”, in order to the skin into a bronze color for beauty. So is excessive sun exposure good for our skin? In fact, not, excessive or too strong sun exposure, the most common will cause the exposed parts of the skin redness, swelling, pain, pimples and other symptoms of sunburn and sunburn, mainly due to sunlight in the wavelength of 290 ~ 320nm medium-wave ultraviolet radiation caused by excessive exposure. Long-term excessive sun exposure will cause premature aging of the skin, the skin becomes more and more rough, producing deep wrinkles that can not be restored, so that the skin produces dark spots, freckles and even induce skin cancer. Such as long-term exposure to the outdoor work of the population, such as seafarers, day-long labor farmers and other groups will even appear sunlight keratosis and other pre-cancerous lesions or skin cancer changes. Sun protection is very important. How to sunscreen, prevent skin darkening and photoaging? 1, the correct choice of sunscreen cream: sunscreen cosmetics roughly divided into physical sunscreen and chemical sunscreen, the former main ingredient is zinc oxide, peptide dioxide, the latter has benzophenone cream, 5% p-aminobenzoic acid alcohol and so on. Sunscreen cosmetics sunscreen effect is mainly to sunscreen factor (SPF) as a standard. SPF value is sunscreen agent to protect the skin against the occurrence of sun erythema index, due to sun erythema is mainly UVB skin phototoxic reaction, so the SPF value on behalf of the protective effect of UVB index. PFA value is the sunscreen agent to protect the skin against the occurrence of sun tanning indicators, because sun tanning is mainly UVA-induced skin photo-oxidation reaction, so the PFA value represents the protective effect of UVA indicators. Sun Protection Factor (SPF) is not necessarily the higher the better, generally on the skin pigmentation of the darker office workers external SPF between 6 to 8 can be, skin color is easier to cause sunburn can choose SPF>15 times the number of sunscreens, often outdoor sports crowd is recommended to choose both protection against UVB high multiples of the SPF index and has the protection of UVA ultraviolet function of the sunscreen, especially sweat-resistant type of chemical sunscreen The best chemical sunscreen products are sweat-resistant. 2, the correct use of sunscreen cosmetics: 15 ~ 20 minutes before going out evenly coated in the face, limbs and other exposed areas, every 2 ~ 3 hours and then repeated coated once, so that the sunscreen was washed away by sweat to form a film. Do not rub, so as to play the purpose of sunscreen. 3, as far as possible with light-colored long pants: cotton clothes SPF value of about 15 ~ 40; polyester light-colored clothes SPF value of about 7 ~ 10; knitted light-colored clothes SPF value of about 4 ~ 9. Avoid exposure to the sun, especially in the morning from 10 am to 2 pm to avoid going out in the light when it is strong. 4, children’s skin is more delicate, also need sunscreen. Choose physical sunscreen-based, avoid the stimulation of chemical sunscreen. 5, remind such as traffic police and other outdoor long exposure of occupational groups, should pay attention to less consumption of parsley, celery, capers, greens, spinach, amaranth, celery and other photosensitive vegetables, as well as photosensitive drugs too much intake, to avoid excessive sun exposure, a prevent caused by plant – solar dermatitis. When sun exposure is severe, local sunburn and polymorphic sunburn such as erythema and papules may appear, and ice milk can be used to apply wet compresses, and appropriate external application of glycerite lotion or hormone cream.