SPF

Sun Protection Factor — a rating system for sunscreen's effectiveness against UVB radiation.

What is SPF? Sun Protection Factor — a rating system for sunscreen's effectiveness against UVB radiation.

SPF measures how long sunscreen extends safe exposure to UVB rays. SPF 30 means it takes 30 times longer to burn than with no sunscreen. SPF 30 blocks about 97% of UVB. SPF 50 blocks 98%. SPF over 50 provides marginally more protection. For everyday use, SPF 30+; for sustained outdoor activity, SPF 50+. Reapply every 90-120 minutes, more often if swimming or sweating heavily.

References: Wikipedia

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SPF

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