The job of the veins of the leg is to channel blood back to the heart. Since the legs are generally lower than the heart, this process must occur against gravity. To prevent the blood from simply running down hill and pooling in the feet, the larger veins are equipped with a series of tiny one-way valves. For various reasons, mostly due to genetic weakness, these valves frequently fail to close all the way and allow blood to flow towards the feet instead of the heart. This backwards or reverse flow is called reflux. Over time it results in excess pressure (venous hypertension) in the leg and causes small veins to distend grossly into visible varicose veins which bulge out through the skin. The excess pressure also leads to pain, swelling, aching, burning, itching, cramps, superficial blood clots, inflammation and in some people restless legs syndrome. If left untreated long enough, skin changes occur and ultimately open sores or spontaneous bleeding may develop. Varicose veins affect nearly 40 per cent of the population. Due to hormonal factors, women are affected by this condition three times as much as men.