Sclerotherapy involves the injection of a solution into unwanted veins, causing them to scar and collapse, forcing blood to reroute through other, healthier veins.  The collapsed veins are then reabsorbed into the surrounding tissues and eventually fade.  Sclerotherapy is a minimally invasive procedure and is considered the treatment of choice for spider veins of the legs.  It may also alleviate related symptoms, such as aching, swelling and burning.