The Hangover

Then there is the matter of the hangover. The folk remedies for this affliction are many and ancient. In medieval times, the medical School of Salerno was already recommending the hair of the dog.

Si nocturna tibi noceat potatio vini,
Hoc tu mane bibas iterum, et fuerti medicina.

If an evening of wine does you in,
More the next morning will be medicine.

The insidious logic of this remedy is simple. The hangover is in part a mild withdrawal syndrome: the night before, the body adjusted to a high concentration of alcohol throughout its tissues, but by morning the drug is going or gone. Hypersensitivity to sound and light, for example, may be a left-over compensation for the general depression of the nervous system. The higher the peak blood alcohol level reached, and the longer that the peak is maintained, the more drastic the effects on the body, the stronger the compensation, and the more pronounced the aftereffects. Having another drink, then, restores the conditions to which the body had become accustomed, as well as lightly anesthetizing it. But this only postpones the hours of reckoning, and if repeated may eventually lead to alcoholism and the necessity of suffering a true drug withdrawal.

-Harold McGee's On Food and Cooking: The Science and Lore of the Kitchen