- WASHINGTON (AP) -- Scientists have discovered that wrinkles, sagging and
other signs of sun-damaged skin can be caused by ultraviolet A solar rays,
a form of sunlight not blocked by most lotions now on the market.
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- UVA solar radiation turns a natural molecule
on the skin surface into a form of oxygen that speeds up the aging of the
skin, said John D. Simon, a Duke University biophysicist and the co-author
of a study being published Tuesday in the Proceedings of the National Academy
of Sciences.
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- Researchers have long known that sunlight
can cause the skin to wrinkle and turn leathery. But experts said the Simon
study is the first to show why this happens -- and to link it to UVA rays.
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- UVA can be blocked by a few sunscreens,
including zinc oxide, that white goo that lifeguards and other beach lovers
often smear on their noses, Simon said. Some preparations have zinc oxide
in a more transparent form, and more advanced products may now be found.
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- The new study underscores the importance
of using a lotion that blocks both types of ultraviolet radiation -- UVA
and UVB. Right now, most sunscreens focus on protecting against UVB while
doing little to protect against UVA.
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- Missy Gough of the American Academy of
Dermatology said her organization recommends that people use broad-spectrum
sunscreens that have a sun protective factor (SPF number) of at least 15.
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- Consumers should check the label to make
sure lotions contain ingredients that protect against UVA, she said. These
include bezophenone, oxybenzone, sulisobenzone, titanium dioxide, zinc
oxide and avobenzone, a sunscreen chemical recently approved by the Food
and Drug Administration and sold under the brand name Parsol 1789.
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- "This study shows that we have to
pay more attention (to UVA) and to find blockers that are more effective
in that region" of solar radiation, said Janna P. Wehrle, a research
director at the National Institute of General Medical Sciences.
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- Wehrle, whose organization is one of
the National Institutes of Health, called the discovery a major advance
in understanding how the sun ages the skin.
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- Simon's study shows that UVA sunlight
is absorbed by urocanic acid, a natural molecule made by the outermost
skin cells. The sunlight chemically changes urocanic acid and causes it
to create within the cells a type of oxygen free radical, a highly active
molecule that can be damaging to cells.
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- This oxygen radical, said Simon, "degrades
collagen and elastin, which are the major molecules that make up the skin.
This process accelerates photoaging of the skin."
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- By degrading collagen and elastin, he
said, "you decrease the elasticity of the skin. It makes you look
older than you might be."
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- The oxygen free radicals from urocanic
acid also may play a role in skin cancer, but that link has not been proved,
Simon said.
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- "People knew there was something
doing damage, but they couldn't find any molecule that caused it,"
said Wehrle. "By finding this indirect mechanism, with the oxygen
free radical, they have shown how light can cause the skin damage."
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- Although the study did not link the mechanism
to cancer, Wehrle said the research "is a warning flag" that
will need further investigation.
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- "Once you have oxygen free radicals
loose in the skin, they can damage many things," she said.
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- Most experts have warned about cancer
and skin damage caused by the UVB part of sunlight, Wehrle said. As a result,
lotions focus on protecting against that type of solar radiation.
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- Nobody considered UVA a risk until now,"
said Simon. "I would expect development of skin blockers against this
longer radiation wavelength pretty soon."
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- For now, both Simon and Wehrle recommended
long sleeves and hats for people going into the sun.
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- "People would do well to stay out
of the sun in the center of the day," said Wehrle. "People should
be covered more of the time they are outside. Hats are a good idea. Moderation
is the key."
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- Simon said he allows his family "reasonable
exposure" to the summer sun and encourages people to wear hats.
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- People don't need to totally avoid the
beach or pool, he said. They should be "respectful, but not fearful
of the sun. We've got to enjoy our lives."
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