Side Effects of Horse Chestnut

Horse chestnut seed extract is an herbal remedy effective for treating chronic venous insufficiency, according to the U.S. National Institutes of Health (NIH). This disorder can cause varicose veins, leg swelling and pain, itching and skin ulcers. When used properly, horse chestnut seed extract is generally considered safe, but it can have serious side effects otherwise.

Toxicity

• The U.S. Food and Drug Administration (FDA) classifies horse chestnut seed as unsafe because some of its components are toxic. Standardized horse chestnut seed extract should not include significant amounts of these components, and should be safe for adults to use in recommended doses for short time frames, according to the NIH. Unprocessed horse chestnut seeds can cause severe side effects and can even be fatal. Symptoms of horse chestnut poisoning may include confusion, coordination problems, diarrhea, vomiting, weakness, muscle twitching, paralysis, and coma. Horse chestnut use also has been linked to liver and kidney toxicity.

Common Side Effects

• The most common side effects associated with horse chestnut seed extract are gastrointestinal, according to Memorial Sloan-Kettering Cancer Center. They include stomach upset and irritation, nausea and vomiting. Some people have reported headaches and dizziness.

Reduced Blood Sugar

• Animal research with horse chestnut indicates the herb can cause reduced blood sugar, as explained by the NIH. Anyone taking medications such as metformin or insulin for diabetes should monitor blood sugar levels closely when also taking horse chestnut seed extract.

Increased Bleeding

• Horse chestnut may increase risk of abnormal bleeding, according to the NIH. People with bleeding disorders may not be able to take horse chestnut seed extract safely, and the risk is further elevated if taking drugs or supplements with blood-thinning properties, such as aspirin, anticoagulants and Ginkgo biloba.

Allergic Reaction

• As with any herbal remedy, horse chestnut seed extract may cause an allergic reaction in some people. Signs as listed by Drugs.com include rash or hives, itching, trouble breathing, tightness in the chest, and facial or mouth swelling. An allergic reaction to horse chestnut should be considered a medical emergency. Additionally, topical solutions containing horse chestnut seed extract can cause an allergic skin rash.