How do UV rays from the sun affect the skin?

The sun emits two types of ultraviolet (UV) radiation -- ultraviolet B (UVB) and ultraviolet A (UVA) rays -- that are responsible for photoaging and skin cancer.

UVB rays have a shorter wavelength than UVA rays but can still penetrate the surface layers of skin, causing sunburns and damage to deoxyribonucleic acid (DNA).

UVA rays have a longer wavelength and penetrate more deeply into the skin, contributing to the formation of free radicals, which damage skin structures and DNA. This process alters the breakdown and regeneration of collagen, making skin appear tougher, thicker, and more wrinkled. Just a few minutes of exposure will begin to alter collagen production.

Although researchers at one time thought only UVA rays contribute to skin cancer risk, research now reveals that both UVB and UVA rays play a role. Both types of rays damage skin. Skin cancer can occur when, in attempting to repair this damage, the skin's regenerative process fails to work correctly.

Exposure to UVA rays causes tanning, but tans are an indication of skin injury. Tans result from an overproduction of melanin by the skin in an effort to protect the body from the sun's harmful radiation. There is no such thing as a healthy tan.

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UV rays pass through the ozone layer of the atmosphere, and up to 80 percent can come through clouds or pollution too. And they reflect off concrete, just as they reflect off the sand and water at the beach. UVA wavelengths also penetrate windows, so if you're spending time near one (at a restaurant, in your office, in your car, or on a plane), your DNA is getting fried. And UV rays penetrate about two feet into the water, so if you are in the pool or in the ocean, your legs are getting sun.

Of course, the sun is more intense and more dangerous in the summertime, at higher altitudes, in places closer to the equator, and when it directly hits your skin for an extended period of time. But please don't fool yourself into thinking you are safe just because you're in the city (not at the pool), running a quick errand, or driving in your car. Many scientific studies have shown that drivers in the United States who spend a lot of time behind the wheel have an increase of skin cancers and sun damage on their left side (the one nearest the window) due to repeated, cumulative sun exposure. In countries such as England, where the steering wheel is on the opposite side, there are more incidences of skin cancer on the right side. Take it seriously. Remember, UV rays are like a laser gun, ready to destroy your DNA the minute you step outside.

Find out more about this book: Simple Skin Beauty: Every Woman's Guide to a Lifetime of Healthy, Gorgeous...

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