In summer, the most important and basic skincare step is sun protection.
UVA is responsible for damaging the elastic fibers and collagen fibers in the dermis of your skin, and the skin will become fragile and prone to wrinkles. This is photo-aging. Westerners are keen on sun exposure and get healthy wheat-colored, but generally speaking, the skin ages quickly.
UVB is responsible for making your skin red (sunburn). After a sunburn, melanin begins to produce and darken the skin, even leading to the formation of aestates.
Under normal circumstances, ordinary skin will start to become red after 15 minutes when exposed to the sun, that is, the inside of the skin begins to be exposed to inflammation. After the sun is exposed, the melanocytes begin to produce melanin to protect the skin. So we just have to protect the skin from sun irritation first.
SPF 30 means 30 multiplied by 15 equals 450 minutes (7.5 hours). Assuming that it is not sweated or wiped off, then SPF 30 sunscreen can help you resist 97% within 450 minutes UVB damage.
SPF 50 is 50 multiplied by 15 equals 750 minutes (12.5 hours). But the higher the concentration of sunscreen, the higher the SPF index and the bigger the burden on the skin.
So if you seldom sweat and seldom get direct sunlight outdoors, then SPF 30 sunscreen is enough. In fact, for SPF, the role of PA is more important, it is a vital indicator to resist UVA. However, the current sunscreen PA index is 3+ or 4+.
Of course, if the skin is already inflamed after sun exposure, it is not recommended that you do a deep exfoliation, or rub it hard to cause secondary damage to the inflamed skin, whether it is removing makeup or cleansing your face. The cleansing must be gentle.