Horse chestnut trees are native to the Balkan Peninsula (which includes such countries as Albania, Bulgaria, Greece, Romania, and Serbia), but are grown worldwide.
Historically, horse chestnut seed extract was used for joint pain, bladder and gastrointestinal problems, fever, and leg cramps.
Today, people use horse chestnut extract as a dietary supplement for chronic venous insufficiency (when the veins of the lower leg are unable to send blood back toward the heart), hemorrhoids, and swelling after surgery. Preparations made from the trees bark are applied to skin sores.
Usable parts of the plant include the seed, bark, and leaf, but seed extracts are most common.