PAU D'ARCO contains hydroquinone known to be toxic. High doses taken internally may cause liver and kidney damage. Even fairly low doses of pau d'arco can cause dizziness, nausea, vomiting, and diarrhea and can interfere with blood clotting. The tree is endangered. It has been used by the ancient Incas for pain, arthritis, inflammation, fever, dysentery, boils and ulcers.