Hangover symptoms include dry mouth, headache, nausea, and sensitivity to light and noise. These symptoms are partly due to the toxic acetaldehyde produced from alcohol by alcohol dehydrogenase, and partly due to general dehydration. Drinking plenty of water between and after alcoholic drinks can mitigate the dehydration portion of the hangover effect. Other components of the hangover are thought to come from the various other chemicals in an alcoholic drink, such as the tannins in red wine, and the results of various metabolic processes of alcohol in the body, but few scientific studies have attempted to verify this. Consuming a large amount of water is the best way to overcome a hangover.