Horse chestnut, or Aesculus hippocastanum, is a tree native to the Balkan Peninsula.
Horse chestnut contains a substance that thins the blood. It also makes it harder for fluid to leak out of veins and capillaries and weakly promotes fluid loss through the urine to help prevent water retention (edema).
Extract from the horse chestnut seed is a popular dietary supplement commonly used to improve vein health and reduce inflammation.