Sun and the Skin

Dateline: 09/17/98

The mantras and admonitions come in daily: Don't stay out in the sun! Use sunscreen! Prolonged exposure to the sun is very hazardous to your health! Despite these warnings, scientists were not exactly sure how UV radiation damages the skin. New research sheds some "light" on the mechanisms and harmful effects of UV light on the skin.

A molecule produced by the upper layers of the skin, trans-urocanic acid (t-UA), was once thought to be the body's natural protector against the sun. When t-UA absorbs UV radiation, it shifts from its trans form to its cis form. Scientists originally thought that this absorption of UV radiation type B was all that was involved.

It turns out that the t-UA also absorbs in the UV A spectrum. When struck by this type of light, the molecule becomes excited and produces oxygen free radicals, which have been associated with everything from premature aging to DNA damage.

Using photoacoustic spectroscopy, the researchers found that the very end of the UV A spectrum, originally thought to be harmless, produced this excited state.

The focus of the concern about UV radiation was UV B light from which, it was thought, most of the damage to our skin comes. As a result of this study, scientists caution that people should also protect themselves from UV A light.

Scientists have estimated that 80% to 90% of the damage done to the skin through the normal aging process is actually caused by the exposure to UV light sources. Proper protection against the full UV spectrum is paramount in protecting the skin from the devastating effects of UV light.

What do you think? Are current sunscreens effective against the full UV spectrum? If not, are there other products that might be effective against all UV light? Come over to the Biology Forum and share your thoughts, opinions, and feelings.

For other information see:

• UV Skin Damage in a Different Light
  Press release from the National Institute of General Medical Sciences.