Varicose veins are caused by insufficient blood flow in your vascular system, where superficial veins are located, near your skin layer. You may have heard them referred to as spider veins, which are actually a milder form of varicose veins. Spider veins are smaller, and might be shaped like a spider web. Large amounts of blood cells can collect around these veins, and since the oxygen content is low in this blood, blue or purple lines can appear through your skin. 

Spider veins may also appear as red and can even impact the skin on your face. Whereas varicose veins most commonly appear in the legs, but they may show up on other parts of the body as well.