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ADVANCES IN SKIN CARE, Part II
PREVENTING SUN DAMAGE
Timothy J. Mickel, M.D., F.A.C.S.
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What do raisins, sun dried tomatoes and tan, leathery, wrinkled skin have in common? Give up? They have all suffered the ravages of sun damage over time. Fortunately, the first two can easily be put to culinary use, but improving weather beaten skin takes a little work.
As I emphasized in last month's article, the single best thing you can do for your skin is to avoid excessive sun exposure, beginning in the first decade of life. While this is truly a case where an ounce of prevention is worth a pound of cure, the situation isn't unsalvageable just because you baked in baby oil instead of gently browning in sunscreen for the first thirty years of your life. In our last article we discussed the beneficial effects of Retin-A on both aging and sun-damaged skin. In this article we will review the mechanism of sun damage and its consequences on the skin, and focus on how to prevent the problem in the first place.
Believe it or not, having a great tan wasn't always in vogue. In earlier centuries, a dark tan was associated with the working class. Lilly white skin, especially in women, was considered a mark of aristocracy. After all, poets described "fair" maidens, not women who were bronze and weather-beaten. But somewhere along the way things changed. Poet/songwriters of my generation sang of endless summers, California dreamin' and cinnamon girls. Tan skin became a sign of health and vitality. Women preferred tan men and men wanted California girls. So we greased up and laid out to bake, like big turkeys in a solar oven. And we looked great - for a while.
Over time, the invisible radiation in sunlight begins to take its toll. As you may remember from watching Mr. Wizard on television, sunlight contains the entire electromagnetic spectrum of radiation. This includes not only visible light, but also X-Rays, gamma rays, infrared and ultraviolet radiation. As far as we know, only ultraviolet radiation is clinically significant in terms of solar damage to the skin.
The ultraviolet spectrum consists of UVA, UVB, and UVC rays. Our ozone rich stratosphere effectively absorbs the UVC rays so that the sunlight that penetrates to the earth's surface is primarily UVA (95%) and UVB (5%). The UVB rays are the bad rays, accounting for acute sun burns as well as for most of the chronic sun damage and malignant degeneration that occurs in human skin over time. However, recent research has shown that even "good" UVA rays can be bad, in that they can accentuate the acute damage caused by UVB, and markedly enhance the latter's long term detrimental effects on our skin. Tanning beds contain high density bulbs that emit UVA. Heat intensifies the skin damage caused by both types of ultraviolet radiation. So just because you tan in a sun bed, doesn't make you immune to the detrimental effects of ultraviolet radiation.
Over time, excessive sun exposure does several bad things to our skin. "Photoaging" is the medical term for sun damage over time. Where thinning of the skin and degeneration of its components is the hallmark of normal aging, photodamaged skin is actually thicker than normal. Microscopically, this is manifested by thickened, degraded elastic fibers in the dermis and an overall decrease in collagen. Externally, photoaging is characterized by mottled pigmentation ("age spots"), coarseness, wrinkling and laxity of the skin. Sun damaged skin bruises easily and often has small visible spider veins. In the public's eye, sun damaged skin is synonymous with old looking skin. So if you want to look old before your time, bake in the sun, and in the off season visit tanning salons frequently.
Prevention is clearly the best weapon against photoaging. Spending your entire life indoors is the surest way to have young looking skin well past middle age. Since this isn't practical unless you live at the Galleria in Dallas , we have to rely on other methods. Clothing is the simplest, most practical method of sun protection. If clothes and hats are dry and made of tightly knit material, they will block nearly all UVA and UVB radiation. On the other hand, wet T-shirts, loosely woven shirts or hats, and fashionable, see-through garments can allow 30-40% of the ultraviolet rays to pass through. Interestingly, window glass blocks all UVB and about 50% of UVA radiation, an umbrella on the beach reduces exposure only by about half (because of reflection from water and sand), and thin cloud cover reduces ultraviolet radiation by 20-40%. Yes, you can get a sunburn on a cloudy day.
Tanning is our skin's natural protective response to sun exposure. Sunlight increases the amount of melanin in the skin. This brown-black pigment absorbs light energy throughout the ultraviolet spectrum and helps prevent sun damage over the short term. Years of sun exposure can overcome this protective barrier, leading to the skin changes outlined above.
Sunscreens help reinforce our natural defenses by reducing the deleterious effects of UV radiation through absorption or reflection of the rays. Sunscreens are rated by their sun protective factor (SPF), the amount of UVB energy needed to produce a minimal red reaction of the skin through the sunscreen. Sunscreens are either physical reflectors, such as zinc oxide, or chemical absorbers like PABA or other clear compounds. Unless you are near the equator or on a sunny mountain top, any sunscreen with an SPF of 15-20 is probably adequate. There is no firm scientific evidence to support the use of any sunscreen with an SPF greater than 30. But in my opinion, if a little sun protection is good, more is better. So if you want to wear a higher SPF, by all means do so.
This entire article has discussed only the cosmetic effects of photoaging. Perhaps the most significant detrimental effect of years of excessive sun exposure is the increased incidence of all types of skin cancer. If you notice enlargement or darkening of an existing mole, a new dark mole or a red place on your skin that doesn't go away in 6 - 8 weeks, see a Dermatologist. The recent report by the news media that sunscreen does not prevent a form of skin cancer called melanoma was, in my opinion, irresponsible because it will encourage people to draw the erroneous conclusion that sun protection isn't necessary. After all, seat belts don't prevent 100% of traffic fatalities, but no one would recommend taking them out of cars. They improve your chances, and so does sunscreen. Wear it.
Some sunscreens, or the perfumes and carriers added to them, can be irritating or cause allergic reactions. If one type disagrees with you, try another. Remember to apply sunscreen 15-20 minutes before you go outside, so it will have time to absorb, and reapply frequently if you are sweating or jumping in and out of a pool. A variety of well tolerated sun screens, including an SPF 20 clear zinc oxide, are available at Dermatique. Come by for a visit, and find out not only how to prevent sun damage, but also to discuss the options for treating wrinkles, sun spots and the other changes of photoaging.
