Using a sunscreen with an SPF of 15 theoretically prevents reddening 15 times longer - about five hours. Another way to look at it is in terms of percentages: SPF 15 blocks about 93 percent of all UVB rays. SPF 30 blocks 97 percent and SPF 50 blocks 99 percent. They may seem insignificant differences, but if you are sensitive to light, or a history of skin vitamin of health cancer, those extra percentages will make the difference. And as you can see, there is a sunscreen that can block all UV rays. FPS model has some points to consider: First, no sunscreen, regardless of their capacity, remains effective without reapplied every two hours. Second, redness of the skin is a reaction to UVB and says little about the damage UV rays can do. Everyone from six months of age should use a sunscreen every day.

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