We all want to maintain that fresh, glowing face we first saw in the mirror as youths. Collagen injections may be one way to rejuvenate sun-damaged or aging skin.

Your skin contains multiple layers. Just below the outer layer (epidermis) is the second layer, called the dermis. This layer has blood vessels, nerves and hair follicles, but it's mostly made up of a protein called collagen. Collagen is a key support structure in your skin with its network of fibers that provides a framework for the growth of cells and blood vessels. Collagen also is found in cartilage, teeth and bones.

Medical science has harnessed the value of this natural protein and surgeons now use a variety of collagen fillers to ease the signs of aging, fill scars and add volume to enhance the appearance of your face. Collagen fillers were the first type of dermal fillers on the market to be used in aesthetic procedures. One of the most popular treatments is collagen lip injections.

Collagen fillers are derived either from human skin or animals, including cows (bovine) or pigs (porcine):

• Injectable collagen formulas derived from human sources include, Cosmoderm and Cosmoplast.
• Zyderm and Zyplast are forms of purified bovine collagen that, unlike human derived collagen, require allergy testing.
• Evolence is a dermal collagen filler made from purified porcine (pig) collagen and also requires an allergy test.
• A hybrid form of collagen is Artefill (known in Europe as Artecoll). This is a mixture of bovine collagen and homogeneous polymethylmethacrylate microspheres, which are tiny plastic spheres. Those spheres not only create a desired new look, but they also stimulate natural collagen production.
• Another key source for collagen fillers is your own body. Autologen is collagen from your own skin, which is harvested during a previous operation and processed into liquid form. If you have a tummy tuck or another operation in which skin is removed, your skin can be used to extract collagen. It's then sterilized and prepared for re-injection. Your processed liquid collagen can be safely stored for five years and used as needed.
• Isolagen injection is collagen that's also taken from your own skin, but in this method, it's cloned in a lab and processed into liquid form. A piece of skin the size of an eraser is all that's needed. It's sent off to a lab and then returned to your surgeon within a few weeks. A minimum of three injections are recommended at two-week intervals. The first injection will improve your wrinkles by about 15 percent, the second injection by 35 percent, and the third injection by 70 percent. Because live cells are injected, improvement may continue for several months after the last injection.
• One final option is Dermalogen, a form of collagen from human cadaver skin which has been sterilized, purified and processed into liquid form. Two or three collagen injections are recommended at one- to two-month intervals to achieve the best result.