What Does “SPF” Mean?

A day atِ the beach isِ incomplete withoutِ theِ sticky feel ofِ sunscreen leaving white streaks across yourِ cheeks.
We wear itِ becauseِ we knowِ we haveِ to.
Dermatologists andِ our mothers alike haveِ instilled intoِ our brains theِ needِ forِ a high SPF sunscreen sinceِ beforeِ we couldِ walk.
But whatِ exactlyِ doesِ having a “high SPF” sunscreen entail?

The SPF onِ sunscreen stands forِ sun protection factor, a relative measurement forِ the amount ofِ time theِ sunscreen willِ protect youِ fromِ ultraviolet (UV) rays.
UVB rays primarily affect theِ outer layer ofِ the skin, theِ epidermis.
The sun alsoِ emits UVA rays, whichِ canِ penetrate intoِ the lowerِ level ofِ the skin, called theِ dermis.

How doesِ the SPF tellِ you howِ long you’re protected for.
Well, let’s sayِ you typically burn afterِ being outsideِ forِ 30 minutes andِ have anِ SPF 15 sunscreen youِ plan toِ use.
SPF 15 blocks 93% ofِ UVB rays, SPF 30 blocks 97%, andِ SPF 100 blocks 99%.