At night, your skin repairs any damage from the previous

NEW YORK -- At night, while weary eyes are getting a much-needed break, your skin is hard at work. It has to repair all the damage of the previous day and still be ready and refreshed by morning.

"Just because you're resting doesn't mean nothing is happening with your body," says Kenneth Marenus, vice president of biological research at Clinique.

Skin is exhilarated when it kicks into overdrive while most other organs replenish depleted energy supplies by taking a nap.

Circadian rhythms based on a 24-hour, light-dark cycle regulate several molecular functions, including skin-cell repair, explains Erwin Tschachler, the scientific director at Vienna's Epidermal and Sensory Research and Investigation Center.

The center, known as CERIES -- an acronym for its French name "Centre de Recherches et Investigations Epidermiques et Sensorielles," performs research that is used to develop Chanel skin-care products and cosmetics.

"Skin cells divide during the night, replenishing collagen and antioxidants and hence allowing the skin to recover from day time aggressions such as UV rays and pollution," says Tschachler.

But because of its nighttime duties, skin actually is at its most vulnerable while most of us are sleeping: It's when the skin barrier -- burdened by cell rejuvenation -- is at its weakest and the most water seeps out, Tschachler says. (That might explain why bedtime moisturizers are often thicker and heavier than their daytime counterparts.)

Sometimes when we first wake up, we are greeted with "pillow wrinkles," a sign that circulation has been impeded, which means that some parts of the skin were exposed to less oxygen, water and nutrients than other parts, explains Mary The, an aesthetician who owns a skin-care salon in San Francisco.

Gently washing and massaging the face will restore the balance; by using a very drying soap and scrubbing the skin fairly hard, a lot of dead cells will be scraped off, which will open up the skin to better oxygen and carbon dioxide exchange.

You might think this is a good thing, The says, but actually a strong soap also could remove the acid mantle, which is a protective layer of the skin.

Also, more water vapor escapes from the cells -- another undesirable side effect of an intensive wake-up washing.

Overall, though, skin adapts well to the daily trials and tribulations we put it through as long as it follows a fairly regular routine, says Clinique's Marenus. People that wake up and go to bed on a strict schedule often are rewarded with healthy skin, while those who keep sporadic hours or work overnight shifts typically face more problems, he notes.

And when busy people favor fun or work over sleep, their skin suffers.

"People are shrinking their rest cycles. ... This poses a stress on skin," Marenus says. There also is a reduction in the skin-repair rate when people find themselves in stressful situations, such as students during exam periods or an adult going through a divorce, he adds.

Skin-care products aim to make up for the loss of natural repair time by arming the skin with the nutrients -- and chemicals -- to battle accelerated aging.

Chanel's Age Delay Lotion SPF 15, for instance, has its "protocell complex" which aims to stimulate self-defense proteins, while the Ultra Correction Time Fighting Rejuvenation Night Cream is formulated to deliver hydration when skin is predisposed to renew itself.

Clinique's Repairware Intensive Night Cream and the companion lotion use "vital fuel," a manufactured imitation of the natural cellular fuel function, and white birch extract and biosine induce anti-stress proteins. A natural collagen complex, which includes soybean protein and centella asiatica extract, boosts natural collagen and elastin, according to the company.

A DAY IN THE LIFE OF YOUR SKIN

Here's a typical day in the life of one's skin, based on a person who gets up after sunrise and goes to sleep after the evening news, according to Debbie D'Aquino, vice president of product development at Clinique:

4 a.m. The peak renewal time for skin. At night, your skin is freed of external damages and cells can devote their time to rebuild essential components that were depleted during the day. While you sleep, there is an increase in cell renewal and other biological functions in the skin.

This is a good time for a nighttime skin-care treatment to absorb negative energy and facilitate the production of energy for a repair boost.

7 a.m. Skin looks its best, refreshed and renewed and ready for the day.

8 a.m. The environmental assault begins. On your way to work, skin is exposed to damaging elements such as bus fumes, pollution and ultraviolet rays. Even just a little UV exposure, the leading cause of premature aging, can harm skin cells.

This also is when "free radical activity" begins. When the skin experiences environmental stress, radicals move back and forth, resulting in energy depletion.

Protect your skin with sunscreen.

11 a.m. The "EMF attack": Your computer is generating electromagnetic frequencies, which slow down your metabolic process. Anything that slows down your body, also slows down your skin cell activity.

3 p.m. A stressful, two-hour meeting compromises the skin barrier function, resulting in skin that feels more sensitive and begins to show signs of wear and tear.

There is a cause-and-effect relationship between your brain and your skin cells. Just like when you touch something hot and neuropeptides send messages to the brain telling you to move your hand, when you experience mental stress, messages are sent to your skin cells to slow down repair.

6 p.m. If you hit the gym -- or even walk a few blocks from office to home -- skin will reap rewards along with your abs. When you exercise, your body releases endorphins and gains oxygen, and oxygen is a prerequisite for ATP production.

10:30 p.m. Your tank is empty -- and your skin's energy reserve is low. Go to bed so your skin can go to work.