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Sun Protection Factor (SPF)—so what does this really mean?

By / June 21, 2013 / / 0 Comments

Lsunsetast week we discussed the difference between UVA and UVB rays. Today we’ll talk about how to stop those damaging rays. You’ll find various “protection” factors including SPF and protection information against UVA and UVB rays on sunscreen labels.

The SPF factor is actually a formula for determining how long and to what extent you get protection from the sun’s rays.

If you are using an SPF 30 sunscreen, you will get the equivalent of one minute of UVB rays for each 30 minutes you are in the sun. In other words, if you apply SPF 30 sunscreen and spend two hours in the sun, it would be as if you spent four minutes in the sun unprotected.

The higher the SPF factor, the higher the percentage protection. SPF 15 sunscreen filters out about 93% of the UVB rays while SPF 30 filters roughly 97% and SPF 100 is at 99%. As you can see, there is more protection the higher you go, but there is never total protection.

The SPF number only indicates protection from UVB rays. There is no scale or standard to measure UVA rays. You should always look for “Broad Spectrum” labeling when selecting you sunscreen as those types will offer both UVA and UVB protection.

If you are going to be in the sun for long periods of time, reapply sunscreen about every two hours or after sweating or swimming. If your sunscreen is labeled “waterproof” it should provide protection for at least 80 minutes, if labeled “water resistant” you can cut that time in half.

While there is no total protection from the sun, if you apply your sunscreen liberally and frequently, you can enjoy a safe and healthy summertime in the sun.