http://www.webmd.com/balance/features/hangover-helpers
But first, here is the official word on what that booze does to your system. Getting rid of the hangover really comes down to understanding how the body reacts to alcohol in the first place. Alcohol is a diuretic -- that is, it tends to increase urination, and therefore, dries you out, explains alcohol metabolism researcher James Schaefer, PhD, professor at the Union College in Schenectady, N.Y. Drinking plenty of water the morning after helps to compensate for the dehydration.
But that's not all that's going on. Impurities are added to alcoholic beverages during the distillation process, and these contribute to the nasty stomachache you get with your hangover. These impurities are especially high in sweeter drinks and malt liquors. Drinking lots of water, then, does two things: it rehydrates your body and dilutes the impurities left in your belly.
When Brian Wakabayashi was at the University of California, Irvine (UCI), he always made burnt toast a part of his morning-after breakfast.
Schaefer has this explanation for why that helps: Carbon in the charred part of the toast filters the impurities. In fact, people who come into hospital emergency rooms with alcohol poisoning get a potent carbon slurry pumped into their stomachs for the same reason. The burnt toast is a much more moderate version of the same remedy.