You wouldn't go out into the cold with bare feet, would you? Or leave your sunglasses at home during an afternoon at the beach? Or apply a big glob of moisturizer to block out the sun's rays?

Of course not. By now, we're quite good at protecting ourselves from weather extremes. In summer, we know that less is more, except when it comes to sunscreen and the width of hat brims, when more is more. In winter, layering's the trick from top to heel; whether Polartech, silk, cotton or wool, each has appeal.

During ski season, however, common sense can leave us when we bare our most tender parts: our skin, lips and eyes.

Winter skin is already under assault - from dry air, low in humidity; from our daily bathing rituals, which strip protective oils from skin; and simply from the effects of aging, giving rise to itchy, scaly, irritated and just plain dry skin. Add exposure to the sun's ultraviolet (UV) rays reflecting up from snow cover and a bracing gust along the trail, and you're a dermatological disaster. They don't make Chapstick big enough to balm all that.

Skin experts insist that skiers blow the sand off summer suntan lotion and pack it in a winter-activity kit. At the very minimum, they recommend applying a moisturizer with sunscreen containing a sun protection factor (SPF) of at least 15 along with protection against UV-A and UV-B radiation. True sunscreens make an even better choice. Also, apply a good moisturizer to hands and feet before slipping on gloves and socks; your cuticles will thank you later. And treat lips to a layer of balm, preferably one with sunscreen. For a totally rad effect, top with a skim of sun-reflecting zinc, the white goop worn on lifeguards' noses.

On a sunlit snowy day, sunglasses are more than mere fashion: they guard against snow blindness. Snow blindness is a "temporary loss of vision resulting from a burn on the cornea caused by ultraviolet rays reflected off the snow," reports the Feb. 2001 issue of the University of California, Berkeley, Wellness Letter. The public health newsletter recommends sunglasses that block at least 90 percent of visible light and, better yet, 100 percent of UV rays. "Polycarbonate lenses not only block UV rays, but also are the most shatterproof," it adds, a helpful hint for those of us who put fragile items in unforgiving places, like back pockets.

Remember to hydrate. For winter sports enthusiasts, it's easy to lose track of water loss through sweating and exhalation. But the water in your skin comes from within. By the time you feel thirsty, your body is probably parched. By drinking at least eight ounces of water for every 20 minutes of exercise, you'll replenish moisture throughout your body. Hot beverages such as decaffeinated tea and coffee are quenching and warming.

Back at home, there are some things you can do to ease winter skin woes. Long hot daily showers that transport you to tropical climes actually rob your skin's natural oils that keep moisture locked in. "The absence of these oils can increase water loss by 75 percent," writes Jane Brody, author of the Personal Health column in The New York Times. How one quantifies moisture loss - well, who knows? But the number sure is impressive. Brody, writing in her February 13, 2001, column, suggests these alternatives to daily showers: Showering every other day and spot-washing in between; or soaking in a lukewarm bath for 10 minutes.

You'll also want to choose your cleansing and moisturizing products with care. Many soaps are drying, such as deodorant, glycerine, antibacterial and gels. Instead, opt for a mild, unperfumed bar with low alkaline: Cetaphil, Aquanil, Basis, Dove or Oil of Olay are brands mentioned by Brody.

After bathing and while your skin is still damp, apply a generous layer of moisturizer. You might think that skin absorbs moisture from moisturizer, but it's not so. The necessary moisture is already in your skin; moisturizers help to keep it there.

In choosing a moisturizer, buy by price - not packaging and fragrance, advises the UC Berkeley Wellness Letter, January 2001. "Consumer Reports found that the least expensive - Vaseline Intensive Care Dry Skin formula - worked best. (It cost 28 cents an ounce, compared with $16 an ounce for the priciest moisturizer, which did less moisturizing than any of the other products tested.)"

Most of all, beware of moisturizers that advertise themselves as "anti-aging creams." These pricey products may contain alpha-hydroxy acids; the enzymes that help "plump up" skin cells actually amplify sunlight's damaging effects. Read labels carefully. If you use these creams often, double up on your sunscreen protection - no matter the season.