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Light Energy and Sunscreens

By: Peter T. Pugliese, MD
Posted: March 26, 2009, from the April 2009 issue of Skin Inc. magazine.

page 3 of 13

UV light is electromagnetic energy that ranges from approximately 160–400 nm. It is usually separated into three divisions:

1. UVA: 315–400 nm

2. UVB: 280–315 nm

3. UVC: 280– approx. 160 nm.

UVA, UVB and UVC are simply different wavelengths of UV energy. UVA is more commonly known as long wave or black light; UVB can be called medium wave; and UVC refers to short wave or germicidal. UVC does not reach the Earth because it is absorbed in the outer atmosphere, so this article will not cover it. It is the energy in the UVA and UVB range that affects the skin and produces so many problems. It is important to understand that these photons with various energy levels can enter the skin and interact with critical biochemical molecules in the skin.

How UV light interacts with skin