What causes spider veins?

Q: I recently turned 40 and have noticed spider veins forming on the outside of both thighs. What causes this?

A: Spider veins, medically termed telangiectasias, are blue or red capillary veins visible just under the skin surface. Most common in the legs or around the ankles they can appear isolated as solitary fine lines or as branches or webs. They do not turn into larger varicose veins but usually become more numerous or widespread over time. Spider veins are very common but are more frequent in women and get worse with age. Other risks for spider veins include genetics, prolonged standing, obesity, and the hormonal influences of pregnancy, menopause, or certain medications.

Fortunately, spider veins do not pose any significant health risk. They are generally painless although sometimes can cause localized symptoms such as itching or burning. Spider veins are not essential for circulation and treatment is done primarily to improve appearance and occasionally to alleviate symptoms. The most common and effective treatment are vein injections, or sclerotherapy. A tiny needle is used to inject a solution into veins that makes them collapse and fade. The discomfort during treatment is generally minimal, even in patients who have an aversion to needles. Laser treatment is an option for veins that are too small for injections. Spider vein treatments are effective but not perfect, a 60-90% improvement is usual, and sometimes several treatments are needed. Treated veins rarely come back but people with spider veins tend to get them throughout life. Depending on the severity of their veins some people come in every few years or so for maintenance treatments.