For people looking for hangover remedies, tea sometimes makes it to the list of tips, but at other times is advised against. What has become even more complicated is when peppermint tea or ginger tea is being suggested as an effective cure. Which ingredient exactly is working? Is it peppermint and ginger, or is it tea?
According to the director of gastroenterology of Taipei Medical University Hospital in Taiwan, Rui-Xiang Tang, there is no medical evidence yet to support the popular claim that drinking tea is effective to cure a hangover. People who claim its effectiveness may have to attribute the substantial amount of water being washed down that help speed up alcohol metabolism in the body, not attribute to tea leaves themselves. Eliminating alcohol from the body has to rely on the liver and enzymes such as alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH).
He added that because the metabolism of both theophylline (existing in tea leaves) and alcohol need to go through the kidney, so when a significant amount of tea liquor is consumed, the elimination of alcohol from the body slows down. This does not help cure the hangover and the function of the liver is likely to be negatively impacted. Therefore, it's better to avoid drink tea right after alcohol consumption.
Source of the above information can be found here (in Chinese)