6 Secrets to Gorgeous Skin (cont.)

Here are, from top dermatologists and Campbell herself, the secrets to stunning skin.

No. 1 and No. 2: Smoking No, Sunscreen Yes

Imagine two people starting out with the same exact DNA. One smoked and sunbathed, the other avoided both. Would that make a difference in the appearance of their skin?

Researchers have the answer to that, and it's a resounding yes.

A team of experts led by plastic surgeon Bahman Guyuron, MD, of Case Western Reserve University analyzed photographs of the faces of 186 pairs of identical twins taken at the Twins Day Festival in Twinsburg, Ohio. The twins had also filled out detailed questionnaires about their lives and daily habits.

It turns out that siblings who smoked and spent lots of time outdoors without wearing sunscreen looked years older than the brother or sister who shunned cigarettes and tanning. They had more fine lines, deeper and more plentiful wrinkles, and their skin was more mottled.

Bourelly isn't surprised. "Many of the things that my patients complain about -- dull, rough skin, and uneven skin tone -- are related to chronic sun exposure," she says, "and studies have shown that smoking is associated with premature wrinkling."

Her straightforward advice: Wear a broad-spectrum sunscreen that protects against both UVA and UVB rays with an SPF of 30 or higher, even on cloudy days, and reapply every two to three hours you're outdoors.

And, for the sake of your overall health as well as your appearance, don't smoke.

No. 3: Consider Retinoids

Studies have shown that the vitamin A derivatives known as retinoids unplug pores, help clear up acne, reduce fine lines, boost the production of collagen, lighten brown spots and freckles, and improve skin texture.

The retinoids -- which have even been shown to help treat precancerous skin lesions -- is sold by prescription only under names that include Renova, Retin-A, and the generic Tretinoin.

"A retinoid should be the foundation of any topical antiaging regimen," says dermatologist Paul M. Friedman, co-author of Beautiful Skin Revealed: The Ultimate Guide to Better Skin.

Friedman, who is a professor of dermatology at the University of Texas Medical School and also at New York's Weill Cornell Medical College, recommends that men and women make a retinoid part of their evening regimen beginning in their 20s.

The downside is that retinoids can initially cause dryness, flaking, and redness.