The seeds are the source of a saponin known as aescin, which has been shown to promote circulation through the veins. Aescin fosters normal tone in the walls of the veins, thereby promoting return of blood to the heart. This has made both topical and internal horse chestnut extracts popular in Europe for the treatment of chronic venous insufficiency and, to a lesser extent, varicose veins. Aescin also possesses anti-inflammatory properties and has been shown to reduce edema (swelling with fluid) following trauma, particularly following sports injury, surgery, and head injury. A topical aescin preparation is very popular in Europe for the treatment of acute sprains during sporting events. Horse chestnuts also contain flavonoids, sterols, and tannins.

The use of horse chestnut in cultural and traditional settings may differ from concepts accepted by current Western medicine. When considering the use of herbal supplements, consultation with a primary health care professional is advisable. Additionally, consultation with a practitioner trained in the uses of herbal/health supplements may be beneficial, and coordination of treatment among all health care providers involved may be advantageous. Horse chestnut has been used topically to cosmetically improve the appearance of varicose veins. It has also been promoted for relief of swelling or inflammation of joints, tendons, and muscles and hemorrhoids. Horse chestnut has been used orally to improve symptoms of fatigue, and pain, nighttime cramping, itching and swelling in the legs.

The unique actions of Horse Chestnut are on the vessels of the circulatory system. This herb seems to increase the strength and tone of the veins, in particular. It inhibits the enzyme hyaluronidase, and makes veins less permeable and less fragile. Horse Chestnut can improve the tone of veins and increase the flow of blood through them. Horse Chestnut leaves have been used as a cough remedy and to reduce fevers. They were also believed to reduce pain and inflammation of arthritis and rheumatism. Externally, Horse Chestnut has been used as a lotion for pain relief from hemorrhoids, rheumatism, swellings, varicose veins, and leg ulcers. Primary internal uses for Horse Chestnut are for support of capillary weakness, edema, frostbite, hemorrhoids, phlebitis, and varicose veins. Horse Chestnut also helps move congestion, and strengthening the capillaries while decreasing their permeability. Horse Chestnut is also utilized extensively in Europe as an anti-inflammatory agent for a variety of health conditions, in addition to being used for vascular problems. A topical aescin preparation is very popular in Europe for the treatment of acute sprains during sporting events. Scientific studies (randomized double-blind, placebo-controlled) have shown that Horse Chestnut can reduce edema. A clinical study compared Horse Chestnut extract to compression stockings and placebo for varicose veins - both the herbal medicine and the stockings significantly reduced edema of the lower legs compared to placebo.