Horse Chestnut
Summary
Horse chestnut seed extract has its best evidence for chronic venous insufficiency: in a Cochrane review, six trials (502 people) found less leg swelling than placebo, and one trial matched compression stockings. Use is short term (up to 12 weeks). Raw seeds, bark, flowers and leaves are unsafe to swallow; only standardized extracts were studied.
Key facts
- Leg swelling and pain from chronic venous insufficiency (grade B)[1]
- 50 mg aescin twice daily for 12 weeks in the largest single trial[2]
- Raw seeds, bark, flowers and leaves are unsafe orally because they contain a toxic component; standardized extracts have it removed[6]
- The 1986 transcapillary-filtration study tested the branded extract Venostasin retard; the Cochrane review declares no known conflicts[5][1]
- 4 graded human outcomes on this page
- October 10, 2026
How it works
ProposedAescin is thought to reduce fluid leaking out of small blood vessels: a single dose lowered the capillary filtration coefficient of the lower leg by 22% versus placebo in people with chronic venous insufficiency.[5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Leg veins | Grade B | Improved | Meta-analysis · n = 502 · 2012 | 3 rows |
| Male fertility | Grade D | Mixed | RCT · n = 219 · 2010 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Leg volume and leg pain in chronic venous insufficiency | Improved | Grade B | Meta-analysis · n = 502 · 2012 Adults with chronic venous insufficiency (17 RCTs in the review; leg volume pooled from 6 placebo-controlled trials) Form: Oral horse chestnut seed extract (single-ingredient products) · Dose: Doses varied across trials; not given in the abstract · Duration: Short term (trials up to about 12 weeks per NCCIH) Leg volume fell by about 32 mL more than placebo (6 trials, 502 people). Six of seven placebo-controlled trials reported less leg pain. Adverse events were usually mild and infrequent; the authors call for larger, definitive trials. | 23152216 (opens PubMed)Source [1] |
| Lower-leg swelling compared with compression stockings | Improved | Grade C | RCT · n = 240 · 1996 Patients with chronic venous insufficiency Form: Dried horse chestnut seed extract · Dose: 50 mg aescin twice daily · Duration: 12 weeks Lower-leg volume fell by 43.8 mL with the extract and 46.7 mL with class II compression stockings, while it rose by 9.8 mL with placebo; both were better than placebo and judged equivalent. Both were well tolerated. | 8569363 (opens PubMed)Source [2] |
| Sperm quality in varicocele-associated infertility | Mixed | Grade D | RCT · n = 219 · 2010 Chinese men with varicocele-associated infertility (control, surgery and escin groups) Form: Escin (aescin) · Dose: 30 mg every 12 hours (60 mg/day) · Duration: 2 months Sperm density improved in 57.5% of the escin group versus 38.5% of controls (significant); sperm motility improvement did not differ significantly from control. All groups also received other medicines aimed at sperm quality. Mild side effects were infrequent. | 19682880 (opens PubMed)Source [3] |
| Leg swelling in chronic deep vein incompetence | Improved | Grade D | RCT · n = 40 · 1992 Patients with venous edema from chronic deep vein incompetence Form: Horse chestnut seed extract · Dose: Not stated in the abstract · Duration: Not stated in the abstract Leg volume measured by hydroplethysmography fell significantly more with the extract than with placebo, including after provoked swelling; the preparation was well tolerated. | 1621440 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Standardized horse chestnut seed extract | Varies[1][2][6] | No absorption data for the extract in our sources.[6] | Generally well tolerated in trials; reported side effects include dizziness, digestive upset, headache and itching.[6][1] | Chronic venous insufficiency trials up to 12 weeks |
| Escin (aescin) on its own | Varies[3] | No absorption data in our sources.[3] | Very low frequencies of mild side effects in the varicocele trial; no effect on liver or kidney tests reported.[3] | Varicocele-associated infertility trial |
| Raw seeds, bark, flowers or leaves | Varies[6] | Not applicable: not a studied supplement form.[6] | Unsafe orally because they contain a toxic component that standardized extracts remove.[6] | Not studied; unsafe |
Studied doses
Doses studied in human trials ranged from 60 mg of escin per day for 2 months to 100 mg of aescin per day (50 mg twice daily) for 12 weeks; a single 100 mg aescin dose was used in a short filtration study.[3][2][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Prescription medicinesNIH fact sheetNo interaction studies are cited here. NCCIH advises anyone on medicines to talk with a health care provider before using herbal products, because some herbs and medicines interact.[6]
Who should be careful
- Raw plant parts
- The raw seeds, bark, flowers and leaves are unsafe to swallow because they contain a toxic component; only standardized extracts were studied.[6]
- Pregnancy and breastfeeding
- Little is known about whether horse chestnut seed extract is safe during pregnancy or breastfeeding.[6]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety first
Only standardized seed extracts belong in a supplement; the raw plant is unsafe to swallow.
- Toxic raw plant
- NCCIH states the raw seeds, bark, flowers and leaves are unsafe orally because of a toxic component.[6]
- Side effects
- Dizziness, digestive upset, headache and itching are reported with extracts; adverse events in trials were usually mild and infrequent.[6][1]
- Duration
- Research use has been safe for up to 12 weeks; longer-term safety is not established in our sources.[6]
How to read the label
- Label dose vs clinical doseTrials gave 50 mg of aescin twice daily; check that the label states aescin content, not just extract weight.[2]
- Standardized extract onlyProducts should be standardized seed extracts, which have the toxic component removed; raw seed products are unsafe.[6]
- Not a substitute for compressionOne trial found the extract equivalent to compression stockings for swelling, but the Cochrane authors call for larger trials.[2][1]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
Enter the price, servings and the amount per serving from your label.
Frequently asked questions
Does horse chestnut help leg swelling?
In a Cochrane review, horse chestnut seed extract reduced leg volume by about 32 mL more than placebo across six trials in people with chronic venous insufficiency.[1]
Is it as good as compression stockings?
One 12-week trial of 240 patients found swelling fell about the same with the extract (50 mg aescin twice daily) as with class II stockings; more trials are needed.[2][1]
Is horse chestnut safe?
Standardized seed extracts are likely safe for short-term use (studied up to 12 weeks). The raw seeds, bark, flowers and leaves are unsafe to swallow.[6]
Sources
- [1]Horse chestnut seed extract for chronic venous insufficiency.. Cochrane Database Syst Rev, 2012. meta-analysis
- [2]Comparison of leg compression stocking and oral horse-chestnut seed extract therapy in patients with chronic venous insufficiency.. Lancet, 1996. RCT
- [3]Escin improves sperm quality in male patients with varicocele-associated infertility.. Phytomedicine, 2010. RCT
- [4]Medical edema protection--clinical benefit in patients with chronic deep vein incompetence. A placebo controlled double blind study.. Vasa, 1992. RCT
- [5][Effects of horse-chestnut seed extract on transcapillary filtration in chronic venous insufficiency].. Dtsch Med Wochenschr, 1986. crossover-RCT
- [6]Horse Chestnut: Usefulness and Safety (last updated April 2025). National Center for Complementary and Integrative Health (NCCIH), 2025. fact-sheet
- [7]Horse-chestnut seed extract for chronic venous insufficiency. A criteria-based systematic review.. Arch Dermatol, 1998. systematic-review
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its PubMed abstract. Official source opened: NCCIH Horse Chestnut page (last updated April 2025). Superseded Cochrane versions (11869657, 15106197, 16437450) excluded in favour of the 2012 update (23152216, no UpdateIn flag). Industry ties: Venostasin retard (branded extract) in the 1986 filtration study; Cochrane review funded by the Chief Scientist Office with no known conflicts; funding for the 1992, 1996 and 2010 trials is not stated in PubMed and they have no PMC full text. Retraction, expression-of-concern, erratum and withdrawn checks on all cited PMIDs: none flagged. Page set indexable.