The root cause of all hangovers is, of course, drinking alcohol. If you drink enough and end up with a hangover, it means you've ingested more alcohol than your body can metabolize efficiently. The toxins in alcohol build up in your body and make you feel sick. A chief culprit is a chemical called acetaldehyde. This is an alcohol by-product that research suggests may cause the worst of your hangover symptoms.
Congeners are another cause of hangovers. These are impurities created during the fermentation process in some types of alcohol. Low quality wines and many dark liquors tend to have high levels of congeners. The rule of thumb is the darker your drink, the worse the hangover. Hungover.net's Pain-O-Meter has an amusing list of hangover-inducing alcoholic beverages.
Dehydration is both a cause and a symptom of hangovers. Alcohol is a diuretic, which means it increases urination. The more alcohol you drink, the more water your body loses. Your liver and kidneys need water to process the alcohol, so when you lose water, your body struggles to rid itself of toxins.
The best cure for a hangover is prevention. If you insist on imbibing, be more careful about your intake. Drink no more than one drink per hour. Remember that light-colored drinks will hurt you less. Drink water while you drink alcohol. Having food in your stomach is a good idea because it slows the absorption of alcohol by your body.
Many hangover cures are just old wives' tales. Drinking more alcohol (known as the "hair of the dog") won't help. It simply postpones the inevitable. Caffeinated drinks like coffee are diuretics, so avoid them if you're hung-over. Eating fruits and vegetables can help replenish the nutrients you've lost. Hungover.net recommends B vitamins. Many sources advise against taking acetaminophen (a.k.a. Tylenol) because it could damage your liver if mixed with alcohol. Ibuprofen painkillers are considered a better choice.
Other classic remedies include sports drinks like Gatorade and sugary food and drink. Tomatoes figure prominently in hangover cures, from Bloody Marys to V8 to Italian food. Some swear that exercise (even sex!) is a great way to get the blood pumping and move toxins out of the body. The amino-acid supplement cysteine may help your liver break down alcohol, too.
Medical research has shown that what you really need to get rid of a hangover is restful time for your body to heal. Plenty of water will help you feel better. Just remember to take it easy at the bar, and try to avoid problems next time.