If they are stretch-marks, then there isn't really anything that you can do once you have them. Stretch-marks are scar tissue from where the skin does not grow at the same speed as the body part that it is encompassing, and stretches the connective tissues causing scarring. Stretch marks can be minimized during the time when they are being created (growth spurts, pregnancy, etc.) with such things as vitamin E oil and cocoa butter, but once they are there just like any other scar tissue, there isn't a whole lot that can be done about them.