The raw seeds, bark, flowers, and leaves of horse chestnut contain toxic compounds and are therefore unsafe for use internally unless using an extract that has been standardised to remove the toxic constituents (3). 

For this reason, it is best to source horse chestnut extracts from reputable suppliers. There are many horse chestnut seed products that are safe for internal and oral use as they have either been standardised or the toxic compounds have been removed. These can be found in most independent health food stores and appear to be safe for short-term use. It is important to note that no parts of the horse chestnut tree should be eaten raw as it contains significant amounts of a poison called aesculin and can be fatal if significant quantities are eaten raw (3).

Many capsules and standardised extracts can be taken internally. These are often marketed for the treatment of varicose veins or other localised conditions where the veins become enlarged, dilated, and congested (2).

Horse chestnut extracted in a gel, cream or ointment is used to treat haemorrhoids and varicose veins. Horse chestnut works by protecting the small veins and capillaries due to its antioxidant tannin content (2). The topical use of horse chestnut is safe providing used on unbroken skin.

Both the extract of horse chestnut and the topical preparations of horse chestnut are used to relieve symptoms of discomfort and heaviness of legs related to minor venous circulatory disturbances and for relief of signs of bruises, such as local oedema and haematoma (1).

Horse chestnut topical preparations offer relief from night cramps and congestion in the lower limbs, classified by pain, itching and swelling as well fatigued, heavy legs (5). It may also be used for restless leg syndrome (7).

The energetics of horse chestnut are cool and dry as well as being powerfully bitter and astringent. The dynamic effect of horse chestnut makes it an important protector of vascular structures and microcirculation. 

In TCM (Traditional Chinese Medicine) it is specifically indicated for the liver and bladder meridians. It is also referenced as a medicine that tonifies and moves the blood, stopping bleeding (6) due to its ability to heal and support the vascular walls (5).

Horse chestnut combines well with lime flowers and yarrow to strengthen and support the blood vessels, and with chilli or hawthorn to improve circulation.

The first written account of medicinal uses in the West in 1720 referenced horse chestnut as being used to treat rheumatism and rectal complaints (2). In the 19th century it was used for bladder, gastrointestinal disorders, fever and haemorrhoids and leg cramps (2).

In 1960 researchers identified that the anti-oedematous and vaso-protective properties of horse chestnut seed were exclusively attributable to a compound called aescin. Horse chestnut seed extract has since been widely prescribed in Europe for the treatment of venous insufficiency and vascular fragility (4).

Cardiovascular system

Horse chestnut is primarily used for conditions in the cardiovascular system such as chronic venous insufficiency. This condition is characterised by swollen legs, varicose veins, heaviness, pain, tiredness, itching, tension and cramps in the calves (1).

Other conditions where horse chestnut is commonly indicated include haemorrhoids, various veins and post-operative oedema (2).

Horse chestnut has a number of actions enabling therapeutic effects on vascular structures. It increases venous tone and improves capillary resistance and permeability. It tones the veins, decreases oedema through direct localised healing effects on the vasculature, and encourages lymphatic activity, reducing both inflammation and congestion (5).

One of the key compounds involved in horse chestnut’s ability to decrease vascular permeability is aescin. Aescin has been shown to elicit anti-oedematous, anti-inflammatory, and venotonic properties. Horse chestnut increases sensitisation to calcium ions, enhancing venous contractile activity and decreasing capillary permeability. These combined actions improve venous tone thus producing a sealing effect upon the weakened or affected vascular tissues thereby reducing oedema and swelling (2, 5).

Horse chestnut may also be used by herbalists as part of a prophylactic approach for deep vein thrombosis as well as for presentations with a higher risk of developing chronic venous insufficiency (5).

Research including clinical trials, in vivo and in vitro studies have investigated the uses of horse chestnut for many decades. Some of this has been carried out using standardised whole plant extracts as well as isolated compounds of horse chestnut, mainly focusing on its use in diseases of the cardiovascular system. 

Animal studies are not condoned by herbal reality, however, to include research from which some understanding of therapeutic actions can be confirmed, some animal studies have been included.

Chronic venous insufficiency

In a 2012 systematic review encompassing 17 studies, findings demonstrate the effects of horse chestnut seed extract alleviate symptoms associated with chronic venous insufficiency (CVI). Notably, results from one of these studies suggest comparable effectiveness of horse chestnut to wearing compression stockings (3).

Haemorrhoids

In a double-blind, placebo-controlled trial participants with acute symptomatic haemorrhoids were administered horse chestnut seed extract (HCSE) in the form of 40 mg aescin tablets three times daily for two months. The results demonstrated a significant improvement in symptoms with  reduced bleeding within less than a week of treatment confirmed through endoscopic evaluation. 

Out of the 38 patients receiving aescin, 31 (82%) reported notable reduction of pain, itching, burning, and swelling, in contrast to only 11 of the 34 (32%) in the placebo group. Endoscopic assessment revealed a significant reduction in bleeding for 26 patients in the aescin group compared to 13 in the placebo group, along with decreased swelling reported by 29 patients in the aescin group compared to 12 in the placebo group (2).

Deep vein thrombosis

A large-scale, randomised controlled trial was carried out on horse chestnut on 4176 patients with thrombosis lung infection and lung embolism to investigate the prophylactic potential of horse chestnut in post-surgical risk of thrombotic conditions.

Horse chestnut was administered intravenously at 10ml a day in the treatment group, the control received either strophanthin or digitalis, vitamin B complex and vitamin C for 4 days prior to surgery and 7 days post surgery. The study results showed that horse chestnut significantly reduced the incidence of deep vein thrombosis after surgery (5).

Male infertility

Limited research has explored the potential benefits of horse chestnut seed extract in addressing male infertility linked to varicocele (swelling of veins inside the scrotum) as well as irritable bowel syndrome. However, the available information is insufficient to make definitive conclusions about its efficacy for either condition. Further research and larger-scale clinical trials are required to elucidate the potential of horse chestnut as a treatment option for these conditions (3).

The common name, ‘horse chestnut’ is thought to originate from the resemblance of brown conkers to chestnuts and the horseshoe-shaped mark, complete with spots resembling horseshoe nails, left on the twig when the leaves shed in autumn.

One of the key active constituents in horse chestnut ‘aescin’ (or escin) is a registered drug in Germany. It is prescribed both topically and orally for the treatment of peripheral vascular diseases (5).

Horse chestnut is native to parts of southeastern Europe. It is thought to originate from the Balkan Peninsula.

According to the IUCN Red List of Threatened Plants Status horse chestnut is classified as vulnerable as its population is decreasing. It is affected by deforestation, exploitation, mining, tourism development and other threats, even in some protected areas. Populations are considered to be severely fragmented. The IUCN (7) states ‘the species has been assessed as threatened across most of its native range. It is Endangered in Bulgaria and critically endangered in Albania. In Greece, the declining population is estimated at less than 1,500 adult trees, whilst in Albania, the population does not exceed 500 individuals (7)’.

Habitat loss and over-harvesting from the wild are two of the biggest threats faced by medicinal plant species. There are an increasing number of well-known herbal medicines at risk of extinction. We must therefore ensure that we source our medicines with sustainability in mind. 

The herb supplement industry is growing at a rapid rate and until recent years a vast majority of medicinal plant produce in global trade was of unknown origin. There are some very real and urgent issues surrounding sustainability in the herb industry. These include environmental factors that affect the medicinal viability of herbs, the safety of the habitats that they are taken from, as well as the welfare of workers in the trade.

The botanical supply chain efforts for improved visibility (transparency and traceability) into verifiably sustainable production sites around the world is now certificated through the emergence of credible international voluntary sustainability standards (VSS). 

Read our article on Herbal quality & safety: What to know before you buy  and Sustainable sourcing of herbs to learn more about what to look for and questions to ask suppliers about sustainability.

Herbal Medicines are often extremely safe to take, however it is important to buy herbal medicines from a reputed supplier. Sometimes herbs bought from unreputable sources are contaminated, adulterated or substituted with incorrect plant matter.

Some important markers for quality to look for would be to look for certified organic labelling, ensuring that the correct scientific/botanical name is used and that suppliers can provide information about the source of ingredients used in the product.

A supplier should be able to tell you where the herbs have come from. There is more space for contamination and adulteration when the supply chain is unknown.

Horse chestnut is easy to grow. The seeds can easily be found in parks, gardens and arboretums. The seeds are planted in late autumn, before the first frost (Around October to November).

• Carefully open the green spiky seed husks to remove the brown seed (conkers). Submerge the seeds (or ‘conkers’) in a bucket of water, any that float to the top are dead and will not grow.
• Prepare small pots with a mixture of soil and compost (70%/30%) making a 2cm hole in the soil in which to place the seed. 
• The seeds will require 4 hours of sunshine in order to germinate. Water the soil when it starts to dry out. The seeds should sprout in the spring after planting.
• Note: To give your tree seeds that best chance- make sure to keep the pots out of reach from birds and squirrels.
• Once the seedlings have grown to saplings, they will need to be transferred into bigger pots or the ground when they reach roughly 0.3m – which could take up to a year.

1. European Union herbal monograph on Aesculus hippocastanum L., semen Draft -Revision 1. (2008). https://www.ema.europa.eu/en/documents/herbal-monograph/draft-european-union-herbal-monograph-aesculus-hippocastanum-l-semen-revision-1_en.pdf
2. Aesculus hippocastanum (Horse chestnut). (n.d.). https://altmedrev.com/wp-content/uploads/2019/02/v14-3-278.pdf
3. Pittler, M. H., & Ernst, E. (2012). Horse chestnut seed extract for chronic venous insufficiency. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.cd003230.pub4 Aesculus hippocastanum – an overview ScienceDirect Topics. (n.d.). Www.sciencedirect.com. Retrieved November 29, 2023, from https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/aesculus-hippocastanum
4. Bone, K., & Mills, S. (2013). Principles and Practice of Phytotherapy: Modern Herbal Medicine (2nd ed.). Edinburgh Churchill Livingstone, Elsevier.
5. Horse Chestnut (Qi Ye Shu) | East West Healing Academy. (n.d.). White Rabbit Institute of Healing. Retrieved November 30, 2023, from https://www.whiterabbitinstituteofhealing.com/herbs/horse-chestnut/
6. Aesculus hippocastanum. (2011, October 19). The Naturopathic Herbalist. https://thenaturopathicherbalist.com/herbs/a-2/aesculus-hippocastanum-horse-chestnut/
7. Allen (IUCN), D., & Group), S. K. (Cave I. S. (2017, July 20). IUCN Red List of Threatened Species: Horse Chestnut. IUCN Red List of Threatened Species. https://www.iucnredlist.org/species/202914/122961065