It is the seed or conker from the horse chestnut tree which is used medicinally. Horse chestnut seed is astringent, anti-inflammatory, a circulatory stimulant, and a tonic for the peripheral vascular system (1,2). It is used internally and externally to strengthen the walls of the small blood vessels, and is most commonly used to treat varicose veins, haemorrhoids and other issues related to venous insufficiency (1). 

Horse chestnut is an anti-inflammatory tonic for the vascular system, specific for strengthening the venous and capillary walls. This reduces capillary permeability which decreases oedema, and tones the walls of the blood vessels to move congestion by supporting the return of blood from the periphery. This support for the blood vessel walls enhances elasticity, improves blood flow and venous return, which prevents the pooling of blood responsible for varicose veins and haemorrhoids (3).

Horse chestnut can be useful in conditions where local tissue oedema is causing pain, such as compression neuropathies like carpal tunnel syndrome and spinal disk compression, as well as congestive menstrual pain (4). 

The seed can be crushed and made into a tincture or decoction, although internal use requires some caution, and guidance is recommended from a medical herbalist. For external use, a tincture or decoction can be applied directly to the skin as a liniment or compress, or used as an ingredient to make a lotion, balm or gel. 

The saponins in the seed are extracted by soaking the crushed water, which can be used as a soap or detergent substitute to clean clothes, stop mould, and deter clothes moths (1,5,6).

Constituents extracted from horse chestnut seed, particularly aescin, are a common ingredient in cosmetic products, often promoted for skin tightening (7). The tannins will also contribute to this action, and a wash or skin toner can be made from an infusion or a diluted tincture for this purpose.

The pharmacologically active constituents in horse chestnut seed are saponins (collectively referred to as aescin), coumarins and flavonoids (2). 

Horse chestnut has anti-exudative and tightening actions on the vasculature via mechanisms of action related to the anti-inflammatory processes of the body. 

Horse chestnut seed extract has an inhibitory effect on catalytic enzymes such as collagenase, hyaluronidase and beta-glucuronidase, which break down capillary walls (8,9). In chronic pathological conditions of the vascular system, this lysosomal enzyme activity is increased, causing a breakdown of the mucopolysaccharides in the capillary and venous walls (10). The saponins in horse chestnut inhibit the activity of these enzymes, which improves the integrity and function of these vessels by decreasing vascular permeability (8,9,10). This reduction in vascular permeability decreases the filtration rate of small proteins, electrolytes and water into the interstitial space (11). This affects the initial phase of inflammation by exerting a ‘sealing’ effect on capillaries and by reducing the number and diameter of capillary pores, reducing vascular leakage, oedema, and swelling (2).

The triterpene saponin aescin, tones the veins by increasing the sensitivity of calcium ion channels, and enhancing venous contractile activity, resulting in the venotonic action (12). Additionally, these saponins increase venous tone by increasing prostaglandin synthesis in the vascular tissue, which induces contraction of the venous tissues (2). This vasoconstriction increases the venous tone and raises the flow velocity of blood in the veins (8). The contraction of the veins, combined with the decreased permeability of the capillaries improves the peripheral vascular tone and reduces venous swelling and oedema.

The flavonoids and tannins are recognised as having anti-inflammatory and astringent properties, respectively (2). The coumarin aesculin is antioxidant, anti-inflammatory and tonic to the venous vessels (13).

Energetically, horse chestnut is cooling, drying and constricting (5,14).

As a flower essence, horse chestnut is for those who repeat the same mistakes without learning from them (5). It helps people to gain knowledge and wisdom from mistakes, by being more aware and observant of the present moment (15). Failure to learn from mistakes can often be linked to poor boundary setting, and horse chestnut can help enforce healthy personal boundaries (16). It can also be a good remedy for children who are absent minded and need support to be more attentive (15). Matthew Wood considers horse chestnut to be an excellent remedy for obsessive and compulsive thinking, where someone feels they have no control over the thoughts racing around their head (17). 

Horse chestnut has a long history of use for treating many ailments including peripheral vascular issues, haemorrhoids, rheumatism, leg cramps, neuralgia, bladder issues, gastrointestinal disorders, diarrhoea and fever (1,2). It was regarded as a remedy for congestion and engorgement, to ease the associated throbbing sensations and dull aches in any part of the body (4). 

In 1898, horse chestnut seed and bark were listed in King’s American Dispensatory as a tonic, astringent, febrifuge, narcotic, and antiseptic (18). The bark was made into a tea and used for its tonic, astringent, febrifuge, narcotic and antiseptic properties, to treat malaria, fever and dysentery (1,19). Externally, a strong infusion of the bark was applied to “gangrenous and ill-conditioned ulcers”, and an oil made from the powdered seed locally applied to ”neuralgic” and ”rheumatic affections” (18).

In the 1800s, the primary internal use was for neuralgia of the internal viscera, due to vascular congestion, engorgement and stasis, with a sense of soreness, throbbing, and malaise all over the body (18). Horse chestnut was known to exert a specific influence on rectal disorders, such as rectal irritation, haemorrhoids, rectal neuralgia and proctitis, by relieving itching, heat, pain, aching, and spasms (18). The dose of the seed tincture was 5–20 drops (¼–1 ml) (19).

Circulatory system

Horse chestnut is most commonly used to treat conditions arising from venous congestion, such as varicose veins and haemorrhoids (1). The Commission E, which provides therapeutic guides for herbal medicine professionals, approves use for treatment of symptoms of chronic venous insufficiency (CVI), including varicose veins, oedema, pain, feelings of heaviness in the legs, night cramps, itching and swelling (11,20). Herbal medicine practitioners will usually prescribe herbs as combination, bespoke medicines, however horse chestnut seed extract is licensed by the European Medicines Agency for use internally and externally in commercially available herbal medicine products (21). It is approved to treat CVI (characterised by swollen legs, varicose veins, a feeling of heaviness in the legs, pain, tiredness, itching, tension and cramps in the calves), as well as bruises, local swelling and haematoma (21).

Horse chestnut has anti-exudative and tightening actions on the vasculature, which restores functionality of the vein wall, and reduces the oedema and venous swelling associated with these conditions. The actions on the vessels in the circulatory system make horse chestnut uniquely suited to both the internal and external treatment of phlebitis (vein inflammation), varicosities, and haemorrhoids (10). In these chronic pathological vascular conditions, there is increased activity of enzymes which cause a breakdown of the capillary walls (10). The saponins in horse chestnut inhibit these enzymes, decreasing vascular permeability which leads to exudation and oedema and the symptoms of CVI (10,22). The combination of the vascular tonic effect and the improved capillary resilience has been demonstrated in clinical trials to improve symptoms in patients with venous insufficiency (8,23). 

The active constituents are absorbed trans-dermally and orally, although the bioavailability of the saponins across the gastrointestinal tract (GIT) is low (4). For this reason, horse chestnut is often concurrently included in both oral and topical formulas. However, in some individuals, internal use may be contraindicated, and topical use is to be discontinued if the skin is broken, due to the haemolytic effect of the saponins.  

Internally, horse chestnut combines well with:

• Yarrow (Achillea millefolium) to stimulate the peripheral circulation
• Gotu kola (Centella asiatica) to support the connective tissues
• Bilberry (Vaccinium myrtillus) to further support the integrity of the microvasculature
• Prickly ash (Zanthoxylum americanum) as an analgesic which also stimulates the peripheral circulation

Topical application

In cases where horse chestnut may be contraindicated, for example in cases of gastric ulcers or gastrointestinal irritability, external applications are preferable. The additional benefit of an external application is the opportunity to massage the area of swelling and oedema. Rubbing a cream, balm or gel into the skin, massaging towards the centre of the body, provides an additional support to the circulatory flow back to the heart, as well as dissipating the oedema from the surrounding tissues. Other lifestyle advice to support CVI and varicose veins includes the use of compression stockings, avoiding standing for long periods, frequently walking around to support blood flow, and sleeping with the legs on a pillow or elevating the foot of the bed slightly.

Because horse chestnut is so effective at supporting the peripheral blood vessels it also makes an effective external application for spider veins, capillary fragility, and those who bruise easily(6,24). Other topical applications include haematomas, contusions, sprains and rheumatic pains (5,24).  

Deep vein thrombosis (DVT)

CVI, phlebitis (inflammation of veins) and varicose veins carry an increased risk of DVT, with horse chestnut treatment reducing this risk (24, 25,26). Horse chestnut can be recommended for use internally or externally before and during long flights to reduce oedema and for preventing thrombosis (7). Horse chestnut can be used prophylactically before surgical treatment, in those at risk of DVT (22).

Neurological 

Horse chestnut may be indicated in disorders where local tissue oedema may be causing nerve compression, such as trigeminal neuralgia, Bell’s palsy, sciatica, disc lesions and hernia, carpal tunnel syndrome (24). Similarly, horse chestnut supports microcirculation in the skin in cases of diabetic neuropathy and diabetic ulcerated lesions (22).

Digestive system

The astringent tannins (anthocyanidins) are helpful in relieving diarrhoea, but can be constipating for those who are prone (3, 16).

Reproductive system 

In women, horse chestnut can be used to address any blood stasis and venous congestion in the pelvic region which could be causing menstrual pain and dysfunction (26). It can also help to reduce oedema associated with premenstrual fluid retention (26). Horse chestnut can also be used prophylactically or in the treatment of venous problems associated with the use of the contraceptive pill (22). 

Clinical data supports both internal and external use of horse chestnut seed extract for symptoms of chronic venous insufficiency (CVI), such as varicose veins and haemorrhoids.

Many studies have assessed the effects of horse chestnut seed extract in patients with CVI, a common condition which causes oedema of the lower leg (2).

A review of five clinical trials demonstrated the effectiveness of horse chestnut seed extract (20–50 mg aescin) used either internally or externally, in patients with chronic venous insufficiency (CVI) and varicose veins (8). The preparations were effective at reducing lower leg oedema (swelling), and improving leg pain, heaviness, and itching (8). 

A Cochrane review of randomised controlled trials (RCT) reviewed the efficacy and safety of horse chestnut seed extract in treating CVI, compared to either a placebo or compression treatment (23). A total of seventeen RCTs were included in the analysis, using internal doses of standardised extracts equivalent to 100–150 mg aescin daily. The study showed a superior improvement of horse chestnut over placebo, with equivalent efficacy for compression stockings (23). It was concluded that horse chestnut seed can increase venous tone and improve venous return leading to reduced swelling, pain and itching (23).

Mechanistically, a significant reduction of transcapillary filtration has been demonstrated in pharmacological studies involving human subjects, and in various randomised double-blind and cross-over studies (11). These studies demonstrate a significant improvement in the symptoms of CVI, including sensations of tiredness, heaviness and tension, pruritus, pain and leg swelling (11).

The seeds were traditionally used to treat respiratory problems in horses, which is the root of the common name (5,27). The name of the seed or “conker” comes from a game played with snails, called ‘conqueror’ or ‘conche’ (27).

Horse chestnut is native to Albania, Bulgaria, Greece, Turkey, Turkmenistan, Yugoslavia, Western Asia, and has been introduced widely across Europe and North America (1,31). The species is found in deciduous forests, woodlands, rocky slopes, valleys and canyons (30,32). It was introduced into the UK in 1629 and is found in deciduous and mixed woodland, and is widely planted in parkland, large gardens and estates, churchyards, urban streets and village greens (32). Horse chestnut trees occasionally self-seed in scrubby areas, waste ground or rough grassland, and woodland, but are cultivated and naturalised in most temperate regions (7,32).

There is no legislation on the trade of the species from the Convention on International Trade in Endangered Species of Wild Fauna and Flora (33). 

The International Union for Conservation of Nature (IUCN) global assessed Aesculus hippocastanum in 2017 and it is listed as Vulnerable (30). They state that the species is widely distributed in many parts of Europe, but populations are declining and have been significantly damaged by the leaf-miner moth Cameraria ohridella (30). The moth impairs the growth and survival of trees by reducing seed weight, germination rates and seedling growth, which may endanger the long term persistence of the species (30). The species is threatened across most of the native range, it is endangered in Bulgaria, and critically endangered in Albania (30). According to extinction risk predictions, horse chestnut is not currently at risk of extinction (31). Collection of seed for use as herbal medicine and by the pharmaceutical industry presents a threat in Greece, whilst in Bulgaria, seed is primarily collected from cultivated sources (30). Horse chestnut is widely cultivated in Europe, Russia and North America, with cultivated sources being recommended to protect nature habitats (1).

Horse chestnut has no status ranking by Nature Serve, where the distribution across North America has not been assessed (34). It does not appear on the U.S. or Canadian Endangered Species acts, or on the United Plant Savers list of species at risk (34,35). 

In the UK, its distribution is stable, with an increase in areas of Ireland and Northern Scotland due to the planting of trees (32). Horse chestnut is not listed by The Vascular Plant, Red Data List, For Great Britain, and does not appear on the UK Biodiversity Action Plan List of Priority Habitats and Species (37).

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 very safe to take; however, their safety and efficacy can be jeopardised by quality issues. So, it is important to buy herbal medicines from a reputable supplier, from sources known to test their herbs to ensure there is no contamination, adulteration or substitution with incorrect plant matter, as well as ensuring that recognised marker compounds are at appropriate levels in the herbs.

Some important quality assurances to look for are certified organic labelling, the correct scientific/botanical name, and the availability of information from the supplier about ingredient origins. A supplier should be able to tell you where the herbs have come from, what contaminants are not in the herb, and what the primary compounds are.

The fresh seeds can be planted outdoors in autumn, with the scar pointing down into the soil (1). Soaking for 24 hours can aid gemination (1,19). Horse chestnut trees grow rapidly and will tolerate poor soil and varying light conditions, though they will not bear seeds until 20 years of age (1).

Vein-soothing lotion*

Ingredients

• 250 g aloe vera gel or plain base cream
• 10 ml horse chestnut leaf infused oil
• 10 ml calendula oil
• 10 ml horse chestnut seed tincture
• 10 ml yarrow tincture
• 10 ml witch hazel tincture
• 10 ml witch hazel distilled water
• 20 ml peppermint or rosemary essential oil

Instructions

• Place the aloe vera or base cream in a bowl and gradually whisk in the oils, one teaspoon at a time. Use the same method to gradually add the tincture, whisking thoroughly, before adding the essential oil and then finally, the witch hazel water. 
• Apply twice per day to varicose veins, thread veins or haemorrhoids.

* Adapted from Chown and Walker (28)

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