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Sunblock, also known as sunscreen, is a preparation applied to the skin to prevent sunburn by blocking ultraviolet (UV) radiation from the Sun. It is particularly effective against UVB rays, which are the primary cause of sunburn and a major factor in skin cancer. Sunscreens are often described by their Sun Protection Factor (SPF), which indicates how well they reduce exposure to UVB rays. For instance, SPF 15 blocks about 93% of UVB rays, while SPF 50 blocks around 98%. Broad-spectrum sunscreens protect against both UVA and UVB radiation, with UVA contributing to skin aging and damage. Health authorities recommend reapplying sunscreen every two hours or more frequently after swimming or sweating.12

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  1. What Does SPF Mean?
  2. sunblock

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