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Herb library · Herb · Aesculus hippocastanum

Horse Chestnut

A European tree whose seed extract is sold mostly for poor blood flow in the leg veins. A review of 17 studies suggests the extract can ease those symptoms. The raw seeds, bark, flowers, and leaves are toxic.

Traditional use

Native to parts of southeastern Europe; its seeds resemble sweet chestnuts but taste bitter. The seed extract was traditionally used for arthritis, pain and swelling, menstrual cramps, and hemorrhoids. Today it is sold for chronic venous insufficiency (leg pain, swelling, and itch from poor vein flow), irritable bowel syndrome, and male infertility.

What studies show

  • Limited

    Chronic venous insufficiency: a 2012 review of 17 studies suggested the seed extract can improve symptoms, and one study found it about as effective as compression stockings. The reviewers said larger, more rigorous trials are needed.

  • Insufficient

    Male infertility linked to varicocele, and irritable bowel syndrome: only small amounts of research, not enough for definite conclusions.

Be careful of

Cautions

  • NoteThe raw seeds, bark, flowers, and leaves are unsafe to take by mouth because they contain a toxic component. Standardized seed extracts have it removed.
  • AmountStandardized seed extracts are likely safe short term and were used safely in studies for up to 12 weeks.
  • NotePossible side effects: dizziness, upset stomach, headache, and itching.
  • ConditionLiverTox lists horse chestnut as a possible, rare cause of liver injury.
  • PregnancyLittle is known about its safety in pregnancy or while breastfeeding.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

From the old books

What herbals and dispensaries of the past printed. History, in their words.

“Ten grains of the powder of the rinds of the nuts have been asserted to be equivalent in narcotic power to three grains of opium. This claim, however, requires substantiation.”
Harvey Wickes Felter and John Uri Lloyd, King's American Dispensatory (1905), vol. 2, p. 992. See the page of King's American Dispensatory, vol. 2, p. 992 (opens in a new tab) · Read the full passage from King's American Dispensatory, vol. 2, p. 992

Sources

  1. Horse Chestnut: Usefulness and Safety (opens in a new tab) · NCCIH · read September 25, 2026
  2. Horse Chestnut (LiverTox) (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.