Spider veins develop from venous insufficiency which comes from a back-flow of blood in the veins; the pressure causes damage to the vessel walls. Prolonged inflammation, high blood pressure, and obesity are some of the medical causes of spider veins. Sometimes, a non-medical condition causes venous insufficiency. Rubbing or washing the face too hard can cause broken capillaries.
Aging causes the weakening of veins and skin, and the aging skin can make the spider veins more noticeable. Generally, smaller spider veins are reddish, and larger spider veins are bluish. The color of the spider vein stems from the repair capabilities of the veins affected. A broken capillary in younger skin can delegate its function to a larger vein and remain reddish until it repairs. Aging capillaries may not be able to depend on larger veins to do this job if the larger veins are also broken and weak.