Horse chestnut is a type of tree that grows throughout the Northern Hemisphere. In traditional medicine, horse chestnut is used to relieve symptoms such as swelling and inflammation and to strengthen blood vessel walls. Other common uses include: to treat circulatory disorders, diarrhea, haemorrhoids and varicose veins. A tea made from horse chestnut is a staple in Turkish folk medicine and used to relieve upset stomach and pass kidney stones.