Wrinkle, wrinkle on my skin, What's the way to do you in? They're 'only' skin deep, but nothing can make you frown like those folds, creases or ridges on your face that are the not-so-pretty signs of aging. What causes these nasty dents in your once-smooth skin? Generally speaking, our skin constantly repairs itself, using its fibroblast cells to produce new collagen and elastin. But as we get older, a grab-bag of factors causes our connective tissue to become disordered and lose its ability for self-renewal. And as the skin's strength deteriorates, it starts to wrinkle.

Topping the list of skin wreckers that wreak real havoc are smoking and sun exposure, and these you can control. But a few other influences are out of your hands, including heredity (indeed, there are wrinkle-prone families) and skin type (if you're fair and blue-eyed, you do have the curse--sensitive skin that's more susceptible to that harmful sunshine).

To make things even more complicated, you don't just have one kind of wrinkle to worry about: There are four types. First we've got--hold your breath for this mouthful--atrophic crinkling rhytids. These are the small parallel lines that pop up when you knit your brows together, also referred to as furrows. Sun damage is the main trouble-maker here: Exposure to UV rays leads to the release of free radicals, which break down the precious collagen and elastin that provide firmness and structure to our skin--and, alas, it begins to droop. So put up a barrier: Splash on daily SPF sun protection for your face and other exposed areas, like your neck and chest.

Still with me? The second kind of wrinkles are permanent elastotic creases, the fold lines that appear on our cheeks, lips and neck and evolve into permanent wrinkles over time. Again, hanging out in the sun can make these lines more severe, and smoking is also a big culprit for these creases. The awful truth is that smoking releases a variety of chemicals and carcinogens onto your face and into your body. And inhaling the smoke hampers your body from circulating oxygen to your skin, which helps it make healthy skin cells and heal wounds or scars.

The third group of skin saboteurs are the ones generated by your own joie-de-vivre, called dynamic expression lines, which show up around your mouth, eyes (crow's feet), and forehead when you grin, frown, raise your eyebrows or otherwise distort your face. And, clearly, you can't help but create this wear and tear by simply living your life, whether that means laughing at your favorite comedian or pouting when your hero hits the dust.

Last but not least among types of wrinkles are those known as gravitational folds, which happen naturally with age as the structure of our skin starts to loosen and sag. One place you'll really see these pop out is on your eyelids. Once more, chalk it up to the loss of collagen and elastin, leading to dry, crepey-looking skin. These folds will be more apparent to those of you with that enviable, lean-faced, fine-boned look. If you've got more of a Shirley Temple-type face, fuller and more cherubic, the folds won't be so noticeable. Of course, the best way to attack both the lines and the folds is to hydrate your skin--or, as my mom used to say, moisturize, moisturize, moisturize! Hopefully, that home remedy, along with wise words from mommie dearest, will help make you more confident about the skin you're in.