Sunscreen can be divided into chemical sunscreen, physical sunscreen, and bionic sunscreen. Among them, the sunscreen used for chemical sunscreen usually has an SPF value and a PA value. The SPF value is for UVB ultraviolet rays, and the PA value is for UVA ultraviolet rays, the real sun killer. UVA is the most lethal because it can reach the bottom layer of the dermis in the shortest time and accounts for 98% of the ground ultraviolet rays. But whether it is sunscreen or isolation cream, the ingredients that protect against ultraviolet rays are roughly divided into physical ingredients (such as titanium dioxide) and chemical ingredients (such as ultraviolet absorbers). Ultraviolet absorbers can make the skin dry and rough if used for a long time, but there are no ingredients that can cause skin cancer. In general, chemical absorbers emphasize the optical effect of high UV absorption values, and have the effects of preventing erythema, sunburn, and suntan, but excessive dosage often causes strong irritation and damage to the skin, and may cause epidermal cell atrophy, so countries have restrictions on the dosage of chemical absorbers. Physical blockers emphasize their physical reflection and scattering effects, and their sunscreen effect is weak and affects the secretion of sebaceous glands and sweat glands. Therefore, both of these sunscreens have some shortcomings. It should be noted that after using sunscreen or isolation cream, you must use makeup remover to clean, because products with too high a sun protection factor will still be a burden to the skin. |
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