sun protection factor

skincare

Also known as: SPF

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Last updated

July 22, 2026

Quick Summary

Sun Protection Factor (SPF) measures a sunscreen's effectiveness against UVB radiation, a primary cause of sunburn and skin cancer. While often thought of as extending time in the sun, actual protection varies. SPF 15 blocks about 93% of UVB rays, SPF 30 around 97%, and SPF 50 about 98%. Broad-spectrum sunscreens also protect against UVA rays, which contribute to skin aging and damage. It's crucial to reapply sunscreen at least every two hours, or more often if swimming or sweating, as even high-SPF products don't offer complete protection. Ultraviolet radiation, including UVB, is part of sunlight that can harm the skin, but it also stimulates vitamin D production.12

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melanoma
Prevention
…using a sunscreen with an SPF rating of 15 or higher. Children should be particularly careful to avoid sunburns, as an increased risk of developing melanoma has been linked to severe sunburns during childhood. Ultraviolet-sensitive devices that warn of potential overexposure to sunlight in order to prevent sunburn are being…
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…using a sunscreen with an SPF rating of 15 or higher. Children should be particularly careful to avoid sunburns, as an increased risk of developing melanoma has been linked to severe sunburns during childhood. Ultraviolet-sensitive devices that warn of potential overexposure to sunlight in order to prevent sunburn are being…
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What Does “SPF” Mean?
…SPF on sunscreen stands for sun protection factor, a relative measurement for the amount of time the sunscreen will protect you from ultraviolet (UV) rays. UVB rays primarily affect the outer layer of the skin, the epidermis. They are responsible for sunburns and some surface-level skin cancers. The sun also…
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…SPF on sunscreen stands for sun protection factor, a relative measurement for the amount of time the sunscreen will protect you from ultraviolet (UV) rays. UVB rays primarily affect the outer layer of the skin, the epidermis. They are responsible for sunburns and some surface-level skin cancers. The sun also…
Read More