What's in an SPF? - Advanced Physical Medicine
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What’s in an SPF?

Nowadays it seems we cannot get enough SPF. Companies such as Neutrogena have even come out with an SPF 100+. But to what extent are such high levels of SPF really necessary? Here are a few points to clear up some common misconceptions about SPF.

The numbers are misleading

Contrary to popular belief, SPF 100 does not provide twice the protection as SPF 50. For example, SPF 15 shields about 94 percent of UVB rays while SPF 30 shields about 97 percent of rays. Likewise, SPF 45 only blocks about one percent more rays than SPF 30.

Don’t forget the UVA rays

A high SPF does not necessarily ensure adequate protection against UVA rays. UVA rays are those that pass through window glass and penetrate deep into the skin. Wrinkles and aging are attributed to UVA rays. UVB rays, on the other hand, cannot pass through window glass and only affect the top layer of skin. Skin damage from UVB rays is characterized by redness and sunburn. Products containing helioplex in addition to avobenzone/Mexoryl SX are most effective at blocking UVA rays.

Apply and reapply

SPF has nothing to do with how long the sunscreen will last. No matter what the SPF, always reapply your sunscreen every 60-80 minutes. Choose a sunscreen that is water resistant and reapply more frequently when in the water or exercising.

So remember, SPF 100 does not mean 100 percent protection.

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