The horse chestnut (also known as Spanish chestnut or buckeye) is a deciduous tree native to southeastern Europe and commonly cultivated in the U.S. and Canada. The tree grows from 40 to 80 feet in height, and is covered with rough brown bark. Horse chestnut has compound leaves that feature 5 to 7 large, serrated, wedge-shaped leaflets. The tree flowers from May to June, bearing small white, yellow, or red colored blossoms. The fruit is a spiny, spherical capsule that contains 1 to 6 shiny brown seeds. The seeds are used for health purposes.
The principal ingredient in horse chestnut seed extract is aescin (or escin), which is a mixture of triterpene glycosides. The seeds also contain flavonoids and sterols. Horse chestnut extracts are commonly standardized to provide consistent (16 to 20 percent) aescin concentration.
For chronic venous insufficiency, Germany's Commission E Monographs recommends divided doses of standardized horse chestnut extract providing the equivalent of 100 mg of aescin per day. Topical preparations may be applied liberally 3 to 4 times per day. The herb appears to be well tolerated at this dosage range, although minor side effects such as nausea and other gastric complaints have been reported in isolated cases. Topical preparations may cause allergic skin reactions in some individuals.