- Horse chestnut is a tree native to parts of southeastern Europe. Its fruits contain seeds that resemble sweet chestnuts but have a bitter taste.
- Historically, horse chestnut seed extract was used for joint pain, bladder and gastrointestinal problems, fever, leg cramps, and other conditions.
- Today, horse chestnut seed extract is promoted for chronic venous insufficiency (CVI; poor blood flow in the veins of the legs, which may lead to leg pain, swelling, itchiness, and other symptoms), irritable bowel syndrome, male infertility, and other conditions.
- Some studies in people have looked at horse chestnut seed extract for CVI, but very little research has been done on its use for other conditions.
- A 2012 systematic review of 17 studies suggested that horse chestnut seed extract can improve symptoms of CVI. Results from one of these studies suggested that horse chestnut seed extract may be as effective as wearing compression stockings. The reviewers noted, however, that there is a need for more rigorous, large-scale randomized controlled trials to assess the efficacy of this treatment option for CVI.
- Small amounts of research have been done on horse chestnut seed extract for male infertility associated with varicocele (a swelling of veins inside the scrotum) and for irritable bowel syndrome, but there’s not enough information to draw definite conclusions about its effects on either condition.
- The raw seeds, bark, flowers, and leaves of horse chestnut are unsafe because they contain a toxic component. Standardized horse chestnut seed extracts, from which this component has been removed, appear to be safe for short-term use.
- Horse chestnut seed extracts are generally well tolerated but may cause side effects such as dizziness, nausea, and digestive upsets in some people.
- Little is known about whether it’s safe to use horse chestnut seed extract during pregnancy or while breastfeeding. No one—including women who are pregnant or breastfeeding—should consume raw horse chestnut.
Talk to your health care providers about any complementary health approaches before you use. It may be contraindicated with any medications you are currently taking.