Horse chestnut (Aesculus hippocastanum) is commonly used in Europe to treat spider veins and varicose veins. An inherited weakness in the structure of veins, which is seen more frequently in women than in men, predisposes a person to varicosities when veins are subjected to increased pressure over time. The best preventive measures are maintaining a healthy weight, avoidance of prolonged standing, frequent elevation of legs when seated, and conscientious use of elastic support stockings if standing is necessary. Conventional medical and surgical treatments are very invasive and often not successful. Horse chestnut is a promising alternative, and clinical studies have demonstrated that supplementing with horse chestnut seed extract may help relieve the pain and swelling of varicosities. The seeds' active compounds appear to inhibit enzymes that can damage capillary walls, and this also helps strengthen veins. Look for products standardized to 20% eschin content and follow package directions. Horse chestnut seed extract might interfere with Coumadin, and those on anti-coagulant therapy should use it with caution. Although varicosities often can form during pregnancy, women should avoid the herb if they are pregnant or breastfeeding.