Just one dose of a horse chestnut extract (standardized to 20% aescin) caused me to have significant nausea and vomiting. Might there be a problem with the product?

Answer:

Horse chestnut extract is typically used to reduce inflammation and swelling, particularly associated with varicose veins and hemorrhoids. Aescin (or escin) is an anti-inflammatory compound in horse chestnut thought to be responsible for its beneficial effects. Generally, side effects of horse chestnut extract containing aescin tend to be mild (Pittler, Arch Dermatol 1998; Siebert, Int Angiol 2002).

However, aescin can cause stomach irritation, nausea and gastrointestinal tract symptoms in some people (Pittler, Arch Dermatol 1998). By taking the extract in a controlled release formulation, the incidence of irritation may be reduced. So if the product you used was not controlled release, the side effects you experienced may not be unusual.

Other side effects associated with the use of horse chestnut extract include itchiness, headache, and dizziness (Pittler, Arch Dermatol 1998). Also, be aware that horse chestnut may have antiplatelet effects, so people who take blood-thinning medications, such as aspirin, clopidogrel (Plavix), warfarin (Coumadin) and others should consult their physician before using (Heck, Am J Health Syst Pharm 2000).

Be aware that "whole" or raw horse chestnuts should not be consumed as this is dangerous. Horse chestnuts, as well as the bark, leaves, and flowers of the horse chestnut tree contain the toxin aesculin, also known as esculin (as opposed to extracts, from which this toxin is typically removed). Aesculin can cause stomach pain, nausea and vomiting, diarrhea, decreased blood pressure, paralysis, and changes in heart rate or rhythm, and ingestion of this toxin can be fatal. Horse chestnut can also cause allergic reactions, including facial redness, swelling of the face and throat, difficulty breathing, and anaphylactic shock in sensitive individuals (National Capital Poison Center 2024; Yi, Clin Exp Emerg Med 2021 Dec).