Spider veins are small, red, or blue veins that often appear on the legs or face. Varicose veins and spider veins develop when tiny, one-way valves inside the veins weaken causing blood flow accumulation increasing pressure on the walls of the vein. This continual pressure produces weakened vein walls and bulge. These veins are caused by factors such as genetics, weight, pregnancy, and age. Some people have a higher risk of development. Common treatments for spider veins include sclerotherapy, laser therapy, and supplements.