Spider veins are small enlarged superficial blood vessels that appear red or blue. They commonly occur on the legs, but frequently occur on the face or elsewhere Sclerotherapy is used to treat unwanted blood vessels. One of several kinds of solutions, called sclerosing solution, is injected with a very fine needle directly into the blood vessel. This procedure has been used for spider veins since the 1930's and before that for larger veins. The solution irritates the lining of the vessel, causing it to swell and stick together and the blood to thicken. Over a period of weeks, the vessel turns into scar tissue that is absorbed, eventually becoming barely noticeable or invisible.   More Info