Veins are tubes that facilitate the blood circulation in the body. Since they need to carry blood in the direction of the heart only, they have a one-way mechanism valve inside of them that opens and closes to keep blood flowing in the right direction. When these inner valves get damaged, it causes the blood to pool or flow backwards, which is termed as a reflux. On account of this condition the veins begin to get thick, large and distorted, subsequently causing varicose veins. Varicose veins in the legs, is a condition caused by weak or damaged vein walls and valves, or when blood pressure increases inside your veins. This condition can occur due to pregnancy, constipation, a tumor, standing long hours, age, obesity, and family history.