SPF sun protection factor values apply to everyone.
Calculation: assume that the intensity of the ultraviolet light will not change because of the time, a man of no protective measures, stay in the sun for 20 minutes after the skin turns red when he SPF15 sunscreen products, said that may be extended to 15 times time, that is, after 300 minutes the skin will be red. The sun protection factor SPF is a measure of the detection index of sunscreen on the defense capability of the sun’s ultraviolet UVB. “PA +” SPF the marked defensive intensity can be divided into three stages. “+” Sign, the more the better the effect of the anti-”UVA”, “+” represents the double isolation sunscreen effect, “+ +” indicates that four times, “+ + +” represents an eight-fold. So can not only be considered in the choice of sunscreen sun protection factor, but also noted that the balance between the “SPF” and “PA” If the difference is too big, that the skin will sunburn unknowingly.
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Article: SPF What does this mean?