Photoaging

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By peace | January 23, 2008

Sunlight is so-called electromagnetic radiation — energy of many different wavelengths emitted by the sun; it travels through space at the enormous speed of 186000 miles per second. Such energy provides us with the heat and light we need, as well as delivering damaging ultraviolet(UV) rays.

The way in which the sun’s radiation affects us depends on its wavelength, which determines how it is absorbed by the molecules in our different tissues. These tissues include those in the eye responsible for vision and those in the skin, all of which are susceptible to UV injury. Too much exposure to the sun is not good for our skins. A suntan is visible evidence of permanent damage that may ultimately lead to skin ageing and cancer. Repeated exposure to sunlight causes photoageing of the skin — dryness, brown and red blotchiness, sagging and wrinkling — especially in people with fair skin. Doctors estimate that around 90% of all skin cancers are potentially preventable by taking care in the sun.

There appear to be two major ways in which skin may age. The first is genetically programmed, so-called intrinsic or normal aging, affecting the skin all over your body. The second is what is known as photoaging and results from the long-term adverse effects of sun exposure. The degree to which skin photoages is also determined genetically to some extent, in that fair-skinned people who burn easily tend to photoage most rapidly. However, it also depends on how much your skin is exposed to sunlight over the years, whether through normal outdoor activities or sunbathing, or both.

It is possible to judge the effects of any photoaging of your skin by comparing the appearance of your skin on your hips or buttocks with that of your face. Those areas normally covered by clothing are smooth and freckle- and wrinkle-free. Facial skin, in contrast, may be relatively freckled in susceptible people, namely those with fairer skin, particularly if they have had a lot of previous sun exposure, and especially in older people, is often dry, thickened, yellowish, blotched brown, deeply wrinkled and covered with thread veins. Allowing for the normal effects of aging, the difference between skin that is usually covered and skin that is normally exposed is the result of photoaging.

Did You Know?
UV Radiation From The Sun
The UV radiation component of sunlight is small but biologically important, consisting of the wavelengths between 100 and 400 nanometres (nm). These are then further subdivided into three categories:

UVC: 100-290 nm
UVB: 290-320 nm
UVA: 320-400 nm

UVC is completely absorbed by the ozone in the atmosphere and does not penetrate to ground level, so the solar UV radiation that reaches us consists only of UVB(up to 5%) and UVA(95% or more). These percentages are approximate overall values and the relative amounts vary considerably with the time of day and year, latitude and other factors.

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