First, how to scientifically choose sunscreen cosmetics sunscreen index, not the higher the value is better, it is generally recommended that professional women working indoors, housewives, should use SPF10/PA+/PFA2-4 products; outdoor work occupation, noon in outdoor activities, should choose SPF20/PA++/PFA4-8 products; often in the hot sun activities or seawater bathing people, should choose Use SPF30/PA+++/PFA>8 products. Second, how to use sunscreen skin care products according to the occasion, season, time, humidity and other conditions and environment, as long as the skin exposed outside the clothes should be coated with sunscreen, including the neck, chin, ears, arms, calves and other parts; of course, the lips should be more protective, when needed, you can choose lipstick or lipstick with sunscreen function; for hair in addition to wearing a hat, umbrella, etc., before going out to spray on some hair care In addition to wearing a hat, umbrella, etc., spray some hair care before going out, so as to avoid brittle hair, split ends, dryness, discoloration and loss of hair after being subjected to ultraviolet rays. It is best to use sunscreen cosmetics 30 minutes before going out and apply it evenly to the areas that need it. If you spend a lot of time outdoors, you also need to apply every 2-3 hours. Sunscreen cosmetics are also needed for office work, rainy days, cloudy days, and under a general sunshade, but for SPF, do not choose too high. When choosing sunscreen cosmetics it is important to note that not the higher the SPF value the better, the choice should be appropriate. The use of too high sunscreen index cosmetics will affect the skin pores breathing and other functions, increasing the burden on the skin. Once the skin has been sunburned, do not use sunscreen cosmetics again and wait for the skin to recover before using them again. The energy of UV rays reaching the ground changes in different environments. In cloudy weather and overcast days, there are still stronger energy of UV rays reaching the ground, not only in sunny summer, but also in autumn and spring when the energy of UV rays reaching the ground is no less than in summer. Especially UVA, in sunlight, the dose of UVA is 100-1000 times higher than UVB, which exists in any season of the year and at any altitude, and there is little variation in UVA in each season. UVA can penetrate glass, clouds and water.