The climate, the air and the chemicals that surround us also exert pressure on our skin.
Dry air is the worst offender. It simply sucks water from skin, despite the skin's best attempts to keep it. It's a sad cycle: When dry air takes moisture from our skin, its structure changes. Those changes make our skin less able to hold onto moisture [sources: Bonté, Rawlings].
For instance, at low humidity, enzymes that cut connections among cells on the skin's surface, allowing such mild skin-shedding that we can't see it, start chopping deeper in our skin, and our skin flakes [source: Bonté]. Then, water escapes from our skin more easily because the flaking shortens the distance to escape. When the humidity drops below 10 percent, the enzymes that make some of our natural moisturizing factors don't work as well [source: National Weather Service, Bonté]. The stratum corneum dries.
Let's say we're in a city where it's dry and cold. Cold makes us switch on the heater, and the heater dehydrates our skin by dehydrating the air.
If the UV index is high, your skin is under further attack. Like dry air, ultraviolet rays from the sun shut off an enzyme that stocks the stratum corneum with natural moisturizing factors. You don't need a high dose of rays to see the effect. If your skin is reddened by the rays, you've experienced enough [source: Bonté].
You can fight back with common sense. The air can't burglarize skin that it doesn't touch, so when you're outside, shield yourself with a jacket, hat and gloves. If it's too warm for layers, moisturize exposed skin. Inside, if you use a heater, return moisture to the air with a humidifier or a pan of water in the room. Or warm yourself with a blanket. And in the sun (or snow), wear a UV-blocking sunscreen.
We're not done yet: Water can also be a problem. This life-giving liquid doesn't actually dehydrate you; the substances in it do, such as soap. To the teachers, nurses, doctors, dentists and other frequent hand-washers of the world, dermatology professor Aftergut says, "Don't wash your hands excessively. Obviously, if you've shaken hands with someone with the flu, wash your hands. When you start washing your hands 30 to 50 times a day, that's not good. When you do wash, use a gentle, nondetergent-based soap, and moisturize frequently."
In addition to hand-washing, swimming can be a problem. Swimming pools, at least hygienic ones, dry skin thanks to the chlorine. Fortunately, a shower after the pool to rinse off the chlorine usually takes care of it.
Now grab some moisturizer and keep reading for more links to skin stuff you might like.