Unhealthy blood flow in the saphenous vein will cause increase in pressure in the vein and inflammation in the tissue. The inflammation turns the tanning system on and causes areas of the lower leg to appear darker, or to have hyperpigmentation. Treating the venous disease will eliminate the pressure, turn the tanning system off and improve hyperpigmentation.
Spider veins can develop from enlargement of pre-existing veins, heredity, hormone containing medications, hormonal fluctuations, and pregnancy, thus, spider vein are more common in women. Sclerotherapy is the treatment of choice for spider veins on the legs. A safe, painless solution is injected into abnormal veins causing them to shrivel and disappear. Spider veins on the face appear to respond better to laser treatments.
Carolina Vein Center's blog 
Written
on July 11, 2012