Even if you use sunscreen and buy expensive moisturizers, you could still be damaging your skin without even knowing it. Here are some things that can damage your skin:

Smoking. Even just a few cigarettes a day can cause wrinkles and also reduces the amount of zinc in your body, which your skin needs for healing.

Crash dieting. You may not like it, but your skin needs fats! Frequent yo-yo dieting can affect the elasticity of your skin and cause sagging.

Running. High-impact sports can cause sagging and stretching from all that bouncing up and down. Also, running can lead to dehydration, which causes dry skin.

Lack of sleep. Sleep is your body's time to repair itself, so if you're not getting enough sleep it means your body has less healing time.

Cosmetics. Be on the lookout for a nasty chemical called sodium lauryl sulphate (found in some beauty products) -- it can dissolve the natural fat in the skin!