In a study by Chen et al a significant protective effect of orally applied EGCG could be demonstrated in mice with a toxic liver failure caused by tetrachlorohydrocarbons. Otherwise, single cases of hepatotoxicity following application of various forms of green tea polyphenols are known. In the period between 1999 and 2008, 34 such case reports have been published, 29 of which have shown a positive de-challenge and 7 have shown a positive re-challenge. The clinical and pathological symptoms included mild elevations of liver function tests, cholestasis, cholangitis, hepatocellular inflammation and hepatocellular necrosis. The symptoms were usually completely reversible after stopping the medication. One patient died of liver failure. Signs of liver toxicity were recorded between day 9 up to 5 months after beginning a therapy with doses of 187,5 -468,75mg EGCG/day).