Spider veins are dilated small blood vessels that have a red or bluish color. They appear mostly on the legs, occasionally on the face or elsewhere.

They can be short, unconnected lines or connected in a "sunburst" pattern. They may also look like a spider web or a tree with branches. Sometimes they can cover a large area of skin and be quite unattractive.

The cause of spider veins is not known, but family history and jobs that require prolonged standing are common factors. Spider veins appear in both men and women, but more frequently in women. The hormones estrogen and progesterone may play a role in their development. Puberty, birth control pills, pregnancy or hormone replacement therapy, often seem to bring them out.

They also may appear after injury or as a result of wearing tight girdles or hosiery held up with tight bands.

A concentrated salt solution or the new product ASCLERA is injected with a very fine needle directly into the blood vessel. The vessels are close to the surface and the needle used is so small, that the pain from the needle is usually not significant. This procedure has been used for spider veins since the 1930s and before that for larger veins. The solution irritates the lining of the vessel, causing it to swell and close off. Over a period of weeks, the vessel is no longer functioning and is dissolved.

Some blood vessels may have to be injected more than once, some weeks apart. In any one treatment session a number of vessels can be injected.  Over time, people may eventually form some new ones. These can be treated, if desired.

Larger dilated blood vessels called varicose veins may be raised above the skin surface. They may occur along with spider veins.  Standard sclerotherapy does not treat the large, bulging varicose veins.  Patients with those are sometimes referred for other procedures, for medical reasons.

Although unwanted blood vessels carry blood, the great majority of them, especially spider veins, are not necessary. If they are unsightly or uncomfortable, they can be treated by injection of a solution that will cause them to disappear or become much smaller. Depending on the number and caliber of the vessels, a single session may improve them more than 70%. Some people need more than one session.  The vessels that go away over the weeks after a treatment have collapsed and are dissolved over time.  People may eventually develop new spider veins, but this is usually over the long-term.