Spider veins are small, dilated blood vessels near the surface of the skin. They are thin and winding and usually look like little red, blue or purple threads running just beneath the skin. Healthy veins that swell can become spider veins. Spider veins are caused by heredity, pregnancy, and prolonged sitting or standing. Generally speaking, spider veins do not create the health problems or leg discomfort that may be observed with varicose veins. However, there can be an underlying cause that should be addressed before treatment occurs if your spider veins are accompanied by symptoms such as pain, swelling, heaviness, itching, or aching. Spider veins can be treated with visual cosmetic sclerotherapy, topical skin laser, or a combination of both.