Female Beauty

Despite all the warnings to avoid exposure to the sun and to wear sunscreen, scientists don’t really know how the sun damages our skin. Now, they’re a bit closer to the answer.

Two scientists recently discovered that sunlight triggers a harmful reaction when it strikes a molecule in our skin–ironically a molecule once thought to be “nature’s sunscreen.” The work suggests the science behind the sagging, leathery skin typical of long-term sun worshippers, and may also shed light on how ultraviolet light causes skin cancer.“We studied a natural component of human skin exposed to ultraviolet light and uncovered a new chemical reaction that may contribute to aging [of the skin] and cancer,” said Dr. John Simon, who led the study.The sun’s harmful rays come in two flavors: ultraviolet A and ultraviolet B. Evidence mounts that ultraviolet A and B both play a role in causing skin cancer and photoaging, which is characterized by deep, premature wrinkles, thickened skin, and age spots.

Using a cutting-edge technique called photoacoustic spectroscopy, Drs. Hanson and Simon studied urocanic acid’s activity when exposed to light near the tail end of the ultraviolet A range, where the molecule’s reactivity was thought to be harmless. They discovered that when this type of light strikes t-UA, it zaps the molecule into an excited “triplet” state that sparks the creation of oxygen radicals.

Oxygen radicals are chemical rogues blamed not only for premature aging, but also for damaging DNA, suppressing the immune system, and causing some respiratory problems.

The SPF (solar or sun protection factor) in sunscreen refers to its ability to protect against the burning rays of ultraviolet B light. But currently there are no world-wide standards to measure protection against ultraviolet A, which accounts for 95 percent of sunlight that reaches the earth.

The work may also change the way researchers approach similar projects. Instead of studying a biological molecule exclusively under the type of light that it absorbs most, Dr. Simon suggested that scientists may need to expose the molecule to a whole spectrum of light, slice by slice, to fully understand the molecule’s physiological effects.

This research was supported by the National Institute of General Medical Sciences (NIGMS), a component of the National Institutes of Health.

This entry was posted on Thursday, May 25th, 2006 at 1:01 am and is filed under Beauty, Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.