Our tests of over 60 sunscreen lotions, sprays, sticks, and lip balms showed that you can’t always rely on the sun protection factor (SPF) number, a measure of protection from ultraviolet B (UVB) radiation, which is the chief cause of sunburn and contributes to skin cancer. We also tested for protection against ultraviolet A (UVA) rays, which tan and age skin, and also contribute to skin cancer. We found more than a dozen sunscreens that did well enough against both UVA and UVB to recommend.
Sunscreen Buying Guide | By CONSUMER REPORTS
The sun protection factor (SPF) is a relative measure of how long a sunscreen will protect you from UVB rays. Usually, the number is explained as the amount of time it takes an individual’s skin to burn when it’s covered in sunscreen compared to when it’s not. For example, assuming you apply and reapply the sunscreen correctly, if you’d normally burn after 20 minutes in the sun, an SPF 30 protects for about 10 hours. But intesity and wavelength distribution UVB rays vary throughout the day and by location.
Consumer Reports on ‘Concierge’ Medicine
And that calculation does not apply to UVA rays. That’s why you need a broad-spectrum sunscreen that provides protection against both types of UV rays. However, no sunscreen blocks 100 percent of UVA or UVB rays. The breakdown: SPF 30 blocks 97 percent of UVB rays, SPF 50 blocks 98 percent, and SPF 100 blocks 99 percent.
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