防晒知识（Sunscreen knowledge）

防晒知识（Sunscreen knowledge） 防晒知识(Sunscreen knowledge) Ultraviolet light divides three kinds of light waves - UVA, UVB, and UVC. Here's the first science. What are UVA, UVB and UVC?. First of all, because the UVC cannot pass through the atmosphere, there is no UVC on the surface of the earth. There is no discussion about the necessity. We mainly talk about the familiar UVA and UVB. UVA is ultraviolet light that can penetrate human skin through windows, glass and clouds. UVB is outdoor ultraviolet light, which is injected directly into the skin during outdoor activities. UVA and UVB, which are not absorbed by the ozone layer, will shine on the earth's surface, causing damage to our skin. Of these, UVA is the cause of pigmentation and wrinkles in the skin due to sun aging. UVB causes immediate sunburn, redness and blisters. In summer, the content of UVB in the sun is the highest in the four seasons. People who work outdoors often should use SPF sunscreen for 30 to 40, and it is enough for office staff to choose products with a SPF value of 18. Winter, the content of UVB is the lowest in four seasons, the sunscreen SPF value should not be too high. The amount of UVA in the sun varies little with season, so sunscreen used throughout the year should contain a protective component of UVA. As technology advances, sunscreen products, both UVA and UVB, have been developed that prevent sunburn and prevent tanning. Therefore, the bottle of treasure Thailand beach drying for a whole week, not black, that is because sunscreen work done enough Oh ~! UVA is the wavelength range 320 ~ 400 nm wavelength, has a strong penetration, can penetrate the glass, even 9 feet of water; and the seasons of the year, regardless of Yinqing, there are. More than 95% of the daily skin exposure is UVA, so it does most damage to the skin. UVA attacks the dermis through the epidermis, resulting in severe damage to collagen and elastin in the skin, and the ability of the dermis to protect itself is poor, and a small amount of UVA can cause great damage. Over time, the skin produces relaxation, wrinkles, microvascular emergence and other issues. At the same time, it can activate tyrosinase, resulting in immediate melanin deposition and the formation of new melanin, make the skin black, lack of luster. UVA can cause long-term, chronic and long-lasting damage and premature aging of the skin, so it is also called aging rays. UVB causes sunburn in the skin UVB is the wavelength range 290 ~ 320 nm wave, can make leather surface oxidation lipid layer protective effect, make the skin become dry; further the nucleic acid and protein denaturation in epidermal cells, produce acute dermatitis (i.e. sunburn) and other symptoms, the skin becomes red and sore. Serious, such as prolonged exposure to the sun, but also lead to skin cancer. In addition, UVB's long-term damage can also cause melanoma cells to mutate and cause sun spots that are difficult to remove. It should be noted that cloudy days, although UVB is blocked by clouds, but UVA still deep into the dermis. Do not be confused by cloudy days, think UV does not exist. An umbrella, wearing a hat, wearing long sleeved clothes can block the sun, but can not completely isolate uv. To this end, bottles of special bottles to order a pair of color myopia glasses, although it can not measure the specific degree of ultraviolet light, but at least can play a reminder role. Of course, the original intention of bottle treasure is to think, If you go out without contact lenses but directly with glasses, glasses in the sun, will become very bright; a sunglasses will cause blurred vision -- bottle treasure is 500 degrees of myopia ah ah ah ah ah ah ah ah ah and this pair of glasses became UV test index is bonus now. Look, this is the big cloudy glasses, soon become sunglasses. But this is also a little bit bad, that is, the big cloudy day, but the ultraviolet ray is very big, it has a little influence on the sight... - it's too dark... Scientific and clinical trials show that UVB induced skin lesions are immediate and severe, and UVA damage to the skin is chronic. Therefore, the ideal protective products should be high security, small irritation, and more critical is to have the function of resisting UVA and UVB simultaneously. So, how to choose the right sunscreen products? We need to learn to read the index Oh ~! In general sunscreen products, we often see the word "SPF". The SPF value reflects the ability of the product to protect against UVB UVB, that is, sunburn. The higher the degree, the longer the sunscreen time. However, the same SPF number, different skin, effective sunscreen time is not the same. The correct choice is to understand the increase in the number of SPF values per 1 degrees, i.e., an increase of 5 minutes. If you choose SPF15 SPF, you can maintain 15*5 minutes = 75 minutes, sunscreen time. In the choice of SPF value, we can not believe that the higher the value of the better, the province should take some time to paint once. General office workers use SPF15 sunscreen products on the ok. Because less than SPF15 is far short of ultraviolet radiation, SPF is too high and can cause skin allergies. And outdoor workers or go to the beach to play, you need to consider high-value, and even waterproof sunscreen products. The Pa+ index is a protective index for UVA and I on cell aging caused by skin. PA+ index in accordance with the ability to resist UVA I, from low to high, is divided into three levels, namely, PA+, PA++, PA+++. The Pa+ index is defined by the Japanese Ministry of health, medical and health department, PA+ index appeared in Japanese sunscreen products. But in recent years, the index began to be popular around the world, and we can see that many European and American products also face the PA+ index. The highest level of the current index is PA+++. The setting sun of Sanya is beautiful, but the sun on the beach is the most difficult job. In addition to choosing the right sunscreen products, we should also pay attention to some other matters. For example, the sun even daub sunscreen products, it's best to have a sunshade or long sleeved dress, avoid high temperature burn skin; sunglasses is essential, because the eyes are more vulnerable than skin; drink plenty of water; and avoid eat food, such as celery, coriander, and daub lemon, citrus essential oil products remember, avoid light, you straight to the sun, will produce terrible burns oh OK, today's boring science project is here. Specific product recommendations, there will be follow-up, please look forward to ~!