The scorching sun, the blazing sun of summer, we will worry about their own skin is tanned and sunburned, this time we will think of sunscreen, then sunscreen products are numerous at the moment how do we choose? How to use it? 1, sunscreen are labeled SPF or PA, so what do these represent? Most of the sunscreen labeled SPF or PA, SPF (Sun Protection Factor) is to show that prevent UVB damage to the sunscreen effect of the numerical value, PA (Protection UVA) is to prevent UVA to what extent the indicators. UVB in ultraviolet light can reach the epidermis of the skin, is an important band that causes skin tanning, its photobiological and photochemical effects are not as good as UVA, the role of skin photoaging is relatively weak. The longer wavelengths of UVA will penetrate into the deeper layers of the skin, harming the dermis layer of the skin, is an important wavelength causing skin photoaging, can destroy the skin’s thermal insulation ability, resulting in skin roughness, glossy and dull, enlarged pores, the production of fine wrinkles, erythema, capillary dilatation, and other manifestations of skin photoaging.UVA, although it is not easy to sunburn the skin, but it will cause skin aging and lesions, so PA labeling is also Therefore, PA labeling is also getting more and more attention. Summer sunscreen SPF sunscreen factor value applies to everyone, the calculation method is: assuming that the intensity of ultraviolet rays will not change over time, we do not have any sunscreen if we stay in the sun after 20 minutes the skin will become red, when he used SPF15 sunscreen, said that can be extended 15 times the time, that is, in 300 minutes (5 hours) before the skin will be sunburned red. This means that a sunscreen with an SPF of 30 can last up to 600 minutes (10 hours). What does PA stand for? PA stands for how well a sunscreen product protects against UVA. The levels of PA protection are PA+, PA++, PA+++. The more “+”, the better the protection against UVA and the longer the effective protection time. PA+: Indicates that it is effective and protects for about 2 to 4 times as long. PA++: Indicates that it is quite effective and protects for 4-8 times longer. PA+++: indicates that it is quite effective, the protection time is more than 8 times. 2. What is the difference between physical and chemical sunscreens? Physical sunscreen contains some fine particles of solid substances such as titanium dioxide and zinc oxide, it is applied to the skin is very uniform, like a mirror, after the sun irradiation, it will reflect and scatter ultraviolet rays, shielding off ultraviolet rays to achieve the purpose of sunscreen, so as to avoid direct contact with ultraviolet rays on the skin, due to the solid particles of the substance is relatively large, will not be absorbed by the skin, so the burden on the skin is small, relatively safe. At the same time its sunscreen ability is strong on the skin without stimulation. Chemical sunscreen is through the inherent absorption properties of certain wavelengths of light, light absorption into heat or fluorescence and then released, so that light can not enter the skin to cause damage. Commonly used sunscreen ingredients are p-aminobenzoic acid and its esters, salicylic acid benzyl ester, benzophenones, cinnamate esters and so on. It is characterized by transparent and refreshing than physical sunscreen, but the possibility of allergy is a bit greater. 3, what is the correct choice and use of sunscreen? Generally speaking, if it is cloudy, or indoors, you can choose SPF15, PA + sunscreen; outdoor sports, short-term exposure to strong sunlight, such as commuting, the choice of SPF30, PA + + + sunscreen is necessary; summer outdoor sports or a long time in the plateau area, the choice of SPF30 +, PA + + + + sunscreen with strong sunscreen, and every 1 – 2 hours to apply! A truly effective defense against ultraviolet damage to the skin. Many people use sunscreen just randomly painted, and do not know the correct way to use, many of us clean face directly after the sunscreen, so that the skin is not only prone to the phenomenon of greasy, but also has a certain damage to the skin, sunscreen use before the need to do a good job of basic skincare work, after cleansing the face of the first need to use the effect of moisturizing water and lotion, so that to the skin moisturized skin water-oil balance will not be prone to The first thing you need to do is to use a moisturizing water and lotion to moisturize your skin. Then use the sunscreen, take the appropriate amount of sunscreen evenly coated in the entire face, wipe open with a light pat way to let the sunscreen in the face to form a protective film. In addition, the jaw and neck must also be applied evenly, otherwise it will be uneven skin color into a big flower face.