Stretch marks are very difficult to treat. They form when a person grows quickly, gains weight rapidly, or is pregnant. The skin stretches so quickly that the elastic tissue in the skin actually tears. That is why stretch marks don’t go away when the person loses weight or is no longer pregnant. There seem to be genetic factors that make some people more prone to stretch marks than others.
Fractional resurfacing is the treatment of microscopic columns of skin within the treatment area. It doesn’t treat all of the skin at once, which could create a large wound, rather it treats a fraction of the skin at a time. The skin in these fractional zones then heals from the untreated adjacent skin. Ablative fractional resurfacing, with the carbon dioxide laser, appears to be the best treatment option for stretch marks. At the very least you should get some fading and blending into the surrounding skin, and in some people (with multiple treatments) they may go away completely. Fractional lasers that do not use carbon dioxide will give you more subtle results, and will require many more treatments.