Spider veins, known as "Telangiectasia" are dilated capillaries, less than 2 mm in diameter. They may be red, blue or purplish in color, visible as short, unconnected lines each about the size of a large hair. They may appear as sunburst pattern, or they may resemble a spider web or tree with branches. In some people, they occur in a small area and are not particularly noticeable. In others, they may cover a large area of skin and be quite unsightly.

Up to 80% of varicose veins are accompanied by some form of spider veins. Spider veins may exist without the presence of significant varicose veins.