Paraguay tea, Yerba, Yerba mate

Yerba mate contains caffeine and should not be used by those who are sensitive or allergic to caffeine. Excessive consumption of caffeine is contraindicated for persons with high blood pressure, diabetes, ulcers, and other diseases.
Yerba mate should not be consumed excessively and chronically (as it has been documented to increase the risk of certain such cancers as oral and esophageal cancer).
Yerba mate has been reported to have MAO-inhibitor activity in one in vitro study. Those persons taking MAO-inhibitor drugs should use yerba mate with caution to monitor these possible effects.