Friday, May 15, 2015

UVA and UVB

People have a lot of questions (and a lot of confusion) about sunscreen. For this post, I thought I'd tackle UVA and UVB. There is some great in depth information here from skincancer.org, but here are some key points.

UVA
  • Think A for "aging".
  • UVA penetrates the skin deeply and plays a big role in photo-aging the skin and causing wrinkles.
  • The strength of UVA rays is consistent throughout the day, penetrates cloud cover, and glass.
  • Mainly responsible for tanning.
  • The words "broad spectrum" are your only guide to knowing if your sunscreen protects from UVA. Unfortunately, the amount of UVA a sunscreen must protect from to be listed as broad spectrum, did not make it into the FDA monograph.
UVB
  • Think B for "burning".
  • UVB is responsible for damaging the superficial layers of the skin, and causing redness and sunburn.
  • Reflective surfaces like water, snow, and ice can create a "bounce-back" effect - multiplying the amount of UV radiation that hits the skin.
  • UVB is strongest in the US from April to October, between 10am and 4pm, but can burn skin year round- especially at high altitudes.
  • The "SPF" rating on your sunscreen ONLY applies to UVB, and refers to extending the length of time it would take for the skin to first show signs of redness, it does not refer to UVA protection.
*graphic credit - skincancer.org

I'll be breaking down the SPF definition mentioned above in more detail in a future post, when I return after Memorial Day!

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