The horse chestnut tree is widely cultivated for its bright white, yellow, or red flower clusters. Closely related to the Ohio buckeye, this tree produces large seeds known as horse chestnuts. A superstition in many parts of Europe suggests that carrying these seeds in your pocket will ward off rheumatism. More serious medical uses date back to nineteenth-century France, where extracts were used to treat hemorrhoids.


What Is Horse Chestnut Used for Today?  

Serious German research of this herb began in the 1960s and ultimately led to the approval of a horse chestnut extract for vein diseases of the legs. Horse chestnut is the third most common single-herb product sold in Germany, after ginkgo and St. John's wort . In Japan, an injectable form of horse chestnut is widely used to reduce inflammation after surgery or injury; however, it is not available in the United States, and it may present safety risks.

The active ingredients in horse chestnut appear to be a group of chemicals called saponins, of which aescin is considered the most important. Aescin appears to reduce swelling and inflammation. 1,31 It is not exactly clear how aescin might work, but theories include "sealing" leaking capillaries, improving the elastic strength of veins, preventing the release of enzymes (known as glycosaminoglycan hydrolases) that break down collagen and open holes in capillary walls, decreasing inflammation, and blocking other various physiological events that lead to vein damage. 2,3,31

Horse chestnut is most often used as a treatment for venous insufficiency . This is a condition associated with varicose veins, when the blood pools in the veins of the leg and causes aching, swelling, and a sense of heaviness. While horse chestnut appears to reduce these symptoms, no studies have evaluated whether it can make visible varicose veins disappear, or prevent new ones from developing.

Because hemorrhoids are actually a form of varicose veins, horse chestnut is used for them as well, and one double-blind, placebo-controlled study suggests that it may be effective. 31

Horse chestnut may also help improve sperm counts in men suffering from infertility due to varicocele, a type of varicose veins that affects the testicles. 33

Another double-blind study found that a topically applied gel made from horse chestnut may be helpful for bruises. 5 Oral horse chestnut has also been proposed for minor injuries and surgery , 4,31 but published studies on this potential use were not double-blind. (For reasons why double-blind studies are important, see Why Does This Database Rely on Double-blind Studies? )

Finally, horse chestnut is sometimes used along with conventional treatment in cases where the veins of the lower legs become seriously inflamed (called phlebitis ). Note: Phlebitis is potentially dangerous and requires a doctor's supervision.


What Is the Scientific Evidence for Horse Chestnut?  

Venous Insufficiency  

One trial on horse chestnut followed 212 people over a period of 40 days. 15 In this crossover study, participants initially received horse chestnut or placebo, and then were crossed over to the other treatment (without their knowledge) after 20 days. The results showed that horse chestnut produced significant improvement in leg edema, pain, and sensation of heaviness. However, the design of this study was not quite up to modern standards.

A better-designed double-blind study of 74 individuals also found benefit. 16

Good results were also seen in a partially double-blind, placebo-controlled study, which compared the effectiveness of horse chestnut to that of compression stockings, a standard treatment. 17 This study followed 240 people over a course of 12 weeks. Compression stockings worked faster at reducing swelling, but by the end of the study the results were equivalent, and both treatments were better than placebo.

Despite these generally favorable results, a review of 17 randomized trials involving over 1,593 people with chronic venous insufficiency was somewhat less encouraging. In the placebo-controlled studies, researchers found that horse chestnut did reduce symptoms, such as leg pain and swelling. But, the results were inconsistent when the supplement was compared to other treatments, like compression stockings. 32

Oligomeric proanthocyanidins (OPCs), derived from pine bark, have also been studied as a treatment for venous insufficiency. In a small, double-blind trial, OPCs were more effective than horse chestnut for the treatment of this condition. 30


A double-blind, placebo-controlled study of 80 people with symptomatic hemorrhoids evaluated the use of a horse chestnut product providing 40 mg of aescin 3 times daily. 31 The results indicated that use of horse chestnut produced noticeable subjective improvements in pain, bleeding, and swelling within a week; within 2 weeks, the benefits were visible by objective examination.


A double-blind study of 70 people found that about 10 g of 2% aescin gel, applied externally to bruises in a single dose 5 minutes after they were induced, reduced bruise tenderness. 18



The most common dosage of horse chestnut is 300 mg twice daily, standardized to contain 50 mg aescin per dose, for a total daily dose of 100 mg aescin.

Horse chestnut preparations should certify that a toxic constituent called esculin has been removed (see Safety Issues). Also, a delayed-release formulation must be used to prevent gastrointestinal upset.


Safety Issues  

Whole horse chestnut is classified as an unsafe herb by the FDA. Eating the nuts or drinking a tea made from the leaves can cause horse chestnut poisoning, the symptoms of which include nausea, vomiting, diarrhea, salivation, headache, breakdown of red blood cells, convulsions, and circulatory and respiratory failure possibly leading to death. 19 However, manufacturers of the typical European standardized extract formulations remove the most toxic constituent (esculin) and standardize the quantity of aescin. To prevent stomach irritation caused by another ingredient of horse chestnut, the extract is supplied in a controlled-release product, which reduces the incidence of irritation to below 1%, even at higher doses. 20

Properly prepared horse chestnut products appear to be quite safe. 21 After decades of wide usage in Germany, there have been no reports of serious harmful effects, and even mild reported reactions have been few in number.

In animal studies, horse chestnut and its principal ingredient aescin have shown a low degree of toxicity, producing no measurable effects when taken at dosages seven times higher than normal. 21,22 Dogs and rats have been treated for 34 weeks with this herb without harmful effects.

Individuals with severe kidney problems should avoid horse chestnut. 23-25 In addition, injectable forms of horse chestnut can be toxic to the liver. 26 The safety of horse chestnut in young children and pregnant or nursing women has not been established. However, 13 pregnant women were given horse chestnut in a controlled study without noticeable harm. 29 Furthermore, studies in pregnant rats and rabbits found no injury to embryos at doses up to 10 times the human dose, and changes of questionable significance at 30 times the dose. 21

Horse chestnut should not be combined with anticoagulant, or blood-thinning, drugs, as it may amplify their effect. 27,28


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