The seeds of the horse chestnut contain a chemical saponin known as aescin, which in clinical studies has been reported to promote increased blood circulation. Aescin purportedly is able too promote blood circulation through the veins by increasing the tone in the walls of the veins, whereby enabling blood to flow unrestricted. Its ability to promote blood circulation has made horse chestnut a popular treatment, both topically and internally, for both chronic venous insufficiency and varicose veins.