Collagen is used primarily to fill wrinkles, lines and scars on the face and sometimes the neck, back and chest.

The procedure: Treatment with collagen can begin after a skin test determines that you're not allergic to the substance. The collagen is injected using a fine needle inserted at several points along the edge of the treatment site. If a local anesthesia has not been used, you may feel some minor stinging or burning as the injections are administered.

Since part of the substance is salt water that will be absorbed by the body within a few days, the are will be slightly overfilled. You may be asked to hold a hand mirror during the procedure to help decide when you've had enough.

After treatment: Immediately following treatment, you may notice some minor discomfort, stinging or throbbing in the injected area. Occasionally some bruising or swelling will occur, but it is usually minor. Any redness that appears in the injected site usually disappears within 24 hours. However, in some individuals, particularly fair-skinned patients, this redness may persist for a week or more. Tiny scabs may also form over the needle-stick areas; these generally heal quickly.

No bandaging is needed and you are free to eat, drink, and wear makeup with sunblock protection shortly thereafter. There may be some temporary swelling and redness in the treated area which should dissipate within a few days.

Results: As stated earlier, the duration of results from collagen injections is variable. Collagen's longevity depends on the patient's lifestyle and physical characteristics as well as the part of the body treated. In general, the injected material is likely to disappear faster in areas that are more affected by muscle movement.