Spider Veins Causes Spider veins are small, thin veins that appear close to the surface of the skin. They are often red, blue or purple in color and form a web-like pattern. Spider veins can occur in any area of the body, but are most common on the legs and face. [FURL=https://milnerveinandvascular.com/what-causes-spider-veins/]Click Here »[/FURL]