Myth versus Fact: Is a higher SPF number on sunscreen equal to better protection from sun damage to the skin?
SPF is not an easy number to understand for the average consumer, as it makes sense that a higher number should automatically equal better protection. SPF stands for sun protection factor, and it refers to a ratio as to how much longer one can stay in the sun without getting redness and sunburn changes. For instance, if a person can go in the sun for 10 minutes sans sunscreen without burning, a product with an SPF of 15 should allow a person to go in the sun for 150 minutes without burning. There are several caveats to that information:
1) Most people do not apply enough sunscreen to achieve the SPF rating on the bottle. Studies show that people apply about half the sunscreen that they should, in which case, an SPF 50 on the bottle may translate to an SPF of 25 or 30 in real world application. The proper amount is 1 teaspoon for the face, and 1 ounce for the uncovered areas of the body. That’s a lot of sunscreen! To give you an idea what you are up against, a 4 oz bottle of sunscreen should last two people for two applications on a single day. Plus, sunscreens degrade in effectiveness throughout the day, whether by sun exposure, sweating, or water (i.e. pool, beach). In these instances it is important to use water resistant formulations and reapply every two hours (even if water resistant).
2) The higher the SPF, the greater percentage of the sun’s rays that are blocked from reaching the skin. As the SPF number gets higher, there isn’t too much more in the way of suns rays that are blocked. A sunscreen with an SPF of 15 blocks about 94% of the sun’s harmful rays, but an SPF 30 blocks 97%, and SPF 45, 98%. Another way to phrase this is that you are getting 50% MORE protection from an SPF 30 over an SPF 15, and 75% better protection with an SPF 45. When you think of it this way, it seems to reason that you get more protection with a higher SPF, and additional protection is always good. Even with that said, as long as the proper amount of SPF 30 is applied, we are getting excellent sun protection from that.
3) SPF only applies to UVB rays, not UVA rays. It is commonly stated that UVB rays cause more burning and UVA causes more aging. However, both contribute to sun damage, increased risk for skin cancer, and aging. Sunscreens that have “broad spectrum coverage” cover both types of ultraviolet rays.
When choosing a sunscreen, it is best to choose one that feels good to your skin, has an SPF of at least 30, and states “broad spectrum” coverage. When using a sunscreen, be generous in application, don’t forget your ears—and remind people who are balding to treat their scalp—and plan to reapply every two hours.
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