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17 Ιουλ 2023 · SPF is a better predictor of protection against UVB since it is 1000 times more erythemagenic than UVA. An SPF-15 can block 94% of UVB radiation, while an SPF-30 can block 97% of UVB radiation. Substantivity is the ability of a sunscreen to withstand adverse conditions such as water and sweat.
7 Μαΐ 2007 · Because sunburn is primarily a UVB effect, it is possible for a sunscreen product to deliver high SPF while allowing a significant percentage of the incident UVA photons to reach the skin.
23 Μαΐ 2023 · An SPF 30 allows about 3 percent of UVB rays to hit your skin. An SPF of 50 allows about 2 percent of those rays through. That may seem like a small difference until you realize that the SPF 30 is allowing 50 percent more UV radiation onto your skin.
1 Ιουν 2020 · Remember the SPF only refers to the sunscreens potential to block UVB rays and not UVA. SPF numbers range from 2 to 50+. The numbers tell you the time the skin will take to redden with the sunscreen versus the amount of time it will take to redden without the sunscreen.
Dermatologists recommend using a sunscreen with an SPF of at least 30, which blocks 97% of the sun's UVB rays. Higher-number SPFs block slightly more of the sun's UVB rays, but no sunscreen can block 100% of the sun's UVB rays.
18 Μαΐ 2022 · What most people don’t know is that SPF actually has no relation to UVA protection. In fact, UVA protection is measured with a completely different scale called the PA system. In order to get both UVA and UVB protection, you must look for sunscreen products labeled “Broad Spectrum”.
18 Ιουν 2018 · Broad-spectrum sunscreens block UVA rays in the same proportions that SPF blocks UVB. Sunscreen labeling set down by the FDA. Look for “broad spectrum” and an SPF of at least 15 to reduce sun...
