I found this on the net...hope it helps
When skin is burned, cut, scraped, or otherwise injured, special cells called fibroblasts produce a substance called collagen to fill and close the wound. Collagen is a tough, fiber-like protein that makes up the most part of scar tissue. Collagen exists in normal skin, too, but in scar tissue, collagen fibers are more numerous and more haphazardly arranged. This is why scars can appear discolored or otherwise noticeable to the eye. Scars change over time. Some fade on their own, though this may take months to years, while others gradually change color and/or shape.
It's not possible to completely remove a scar, but a few treatments might help make your scars less noticeable:
Onion Extract acts as an anti-inflammatory and seems to inhibit the over-production of collagen in a scar. Onion extract is available in the United States as a gel by itself, but is also an ingredient in Mederma gel, a widely used scar treatment that you referred to in your question. Onion extract, by itself or as part of another course of treatment, requires consistent use over several months in order to produce any effect.
Silicone, available either as a gel or in rubber-like sheets, has been found to lighten and flatten scars. You apply the gel directly to the scar or use medical tape to cover the scar with the silicone sheet. It isn't known exactly how silicone helps scars heal — some researchers think that static electricity from the silicone helps align collagen fibers in the scar, while others think it might help trap moisture, which can help make scars fade.
Alpha Hydroxy Acids are natural fruit acids that are used to exfoliate (remove) dead skin cells. This process can improve the appearance of acne scars and reduce redness, as well as wrinkles and signs of aging. If you decide to use alpha hydroxy, investigate the various strengths and use the mildest. For people with sensitive skin, alpha hydroxy can cause irritation, stinging, and other problems. A health care provider or dermatologist can advise you on which types and concentrations of alpha hydroxy acids you can try.
Product manufacturers say that scar-treatment products will work on both new and old scars, though older scars may take longer to improve, if at all, from the treatment. If you are treating a new scar, wait until the wound is completely healed (i.e., no raw open areas, oozing, or scabs), which may take between three weeks and a few months. Also, use them consistently, as indicated, for periods also up to several months.
Some studies have concluded that over-the-counter scar treatments are 25 - 50 percent effective at reducing the spreading and darkening of scars. In other words, these treatments are effective for some, but not for everyone who uses them. Some treatment brands carry guarantees or product-return policies — if you decide to give one a try, it's a good idea to be aware of the terms of any such policy before purchasing. Also, if price is a concern, consider using silicone strips as a first attempt at treatment — they can be washed and reused, sometimes for an entire course of treatment.
If over-the-counter treatments don't give you the results you're looking for, surgical treatments also might be able to help. Collagen and steroid injections, as well as laser treatment, can all help improve the appearance of damaged skin. Your dermatologist or health care provider can help you decide if surgical alternatives are right for you. Also, if you're interested in trying a non-surgical treatment, but aren't sure where to begin, a health care provider can help with that, too.
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