The aging of our skin is divided into “natural aging” and “photoaging”. “Natural aging” is mainly determined by genes, while “photoaging” is caused by the long-term exposure of our skin to sunlight, for example, we may find that some people have dotted or flaky coffee spots (pigmentation abnormalities), deepened nasolabial folds (sagging skin), fine wrinkles, facial redness, enlarged pores, and dull skin color. For example, we may find that some people have dotted or flaky coffee spots (pigmentation abnormalities), deepened nasolabial folds (skin laxity), fine wrinkles, facial redness, enlarged pores, dull skin color, etc. These are all photoaging phenomena. As we grow older, we cannot resist the erosion of the years, and natural aging is inevitable. So, how to prevent photoaging and slow down skin aging? From the point of view of skin care that is sun protection! Before introducing how to sunscreen, but also to introduce you to some basic concepts. The ultraviolet rays in sunlight are generally divided into: long-wave ultraviolet UVA (mainly cause photoaging and skin tumors), medium-wave UVB (mainly cause sunburn), short-wave ultraviolet UVC (mainly blocked by the atmosphere, can be negligible). This basic concept is particularly important for the following introduction of how to choose sunscreen products. 1, the choice of sunscreen products: sunscreen products from the mechanism of action is divided into physical sunscreen and chemical sunscreen. Physical sunscreen can be simply understood as the external coating of some substances to block UV damage to the skin (to play a physical shielding effect, refraction, scattering ultraviolet rays), its composition is mainly: zinc oxide, titanium dioxide, etc.. Generally speaking, physical sunscreens are thick and greasy, and are applied to the face like “Peking Opera face”. However, physical sunscreens are safe and hypoallergenic, especially for pregnant women, infants and children (it is currently recommended to start using sunscreen for infants over 6 months old). Chemical sunscreen is its chemical composition to absorb UV rays and release them into heat without causing damage to the skin, and its main ingredients are: para-aminobenzoic acid (PABA), etc. Chemical sunscreen is delicate, well absorbed, does not block pores, not easy to form acne, especially suitable for acne patients (oily or combination skin) use, but pay attention to people prone to allergies caution with chemical sunscreen, and to use 20 minutes before going out (need time to absorb). 2, the choice of sun protection factor: choose sunscreen we may know to look at the SPF value (sun protection factor sun protection factor), here to note: First, the SPF value is for UVB sun protection ability, which is the main sun protection factor we mentioned above to prevent sunburn; Second, not the higher SPF value sun protection ability is stronger, SPF value only The SPF value only represents the length of sun protection time. For example, SPF 30 and SPF 60 sunscreen are the same, but SPF 30 sunscreen needs to be reapplied every 2 hours, while SPF 60 sunscreen needs to be reapplied every 3 hours. Generally speaking, the sun protection factor is half decayed in one hour. Therefore, when working outdoors or traveling, it is recommended to choose SPF30+ and reapply it every 2 hours. In fact, we for the prevention of photoaging mainly depends on the sunscreen products on the long-wave ultraviolet (UVA) protection effect that PA (protection of UVA) value, PA is for the UVA sun protection factor. Generally with +, + + +, + + + to express, daily work can choose + +, outdoor activities to choose + + +. 3, sun protection factor can not be superimposed: for example, you apply the moisturizer with SPF15 sunscreen, and outside with SPF30 sunscreen, at this time the sun protection factor is still 30. 4, sunscreen when to apply: half an hour before going out to apply the best effect. Moreover, applying sunscreen should be the last step in the skin care routine (i.e. cleanse, hydrate, moisturizer, and finally apply sunscreen). 5, other protective measures: in addition to the above-mentioned we have to use sunscreen, we also pay attention to wear: (1) sunglasses (to prevent UV damage to the eyes – cataract); (2) sun hat (brim > 125px); (3) UV umbrella.