Varicose veins and spider veins are diseased veins that have become permanently dilated. They can be treated during an in-office, lunch break procedure. The treatment, called sclerotherapy is done by injecting a small amount of solution (called a sclerotic agent) into a varicose vein. The sclerosing solution irritates the lining of the vein and causes the vein to become temporarily inflamed and, eventually, dry up. The vein is replaced with a fibrous tissue that is reabsorbed by the body and disappears.