Spider veins are small, enlarged superficial blood vessels that appear red or blue. They commonly occur on the legs. These dilated blood vessels may be short, unconnected lines, each about the size of a large hair, or connected in a matted, "sunburst" pattern. They may also look like a spider web or a tree with branches. Sometimes they occur in a small area and aren't very noticeable, or they can cover a large area of skin and be quite unattractive.

Larger, dilated blood vessels called varicose veins may be raised above the skin's surface. They may occur along with spider veins. Patients can have pain, ranging from a dull throbbing pain to a burning sensation. The larger vessels are more likely to cause discomfort, although smaller blue veins have been shown to cause pain as well.

If spider veins are unsightly or uncomfortable, we can treat them by the injection of a solution that will cause them to disappear or become much smaller. The injection method, a procedure called sclerotherapy is used to treat unwanted blood vessels on the legs. One of several kinds of solutions, called sclerosing solution, is injected with a very fine needle directly into the blood vessel.

Sclerotherapy has been used for spider veins since the 1930s, and before that for larger veins. The solution causes the veins 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.