The source of the physical and mental pain of the alcoholic hangover is, to repeat, the state of hyperactivity in the central nervous system caused by the withdrawal of alcohol. The cells, which are accustomed to the presence of alcohol and dependent on it for energy, stimulation, and sedation, become agitated when it is suddenly not available. The cells' distress is experienced by the alcoholic as the headache, eyeache, dizziness, nausea, and anguish characteristic of the hangover, ("anguish" is an older term than "anxiety" and refers to both mental and physical pain or suffering -- "anxiety" refers only to psychological conflict or tension).
"Under The Influence" pg. 67
Stickied here, surprised no one quoted it.
I generally defer to 'opinions' that are a little more informed than my own.
My personal experience, a 'hair of the dog' worked wonders for relieving a hangover, far in excess of any analgesic properties that alcohol has.