Sant P. Singh, a professor and chief of endocrinology, diabetes and metabolism at the Chicago Medical School, explains.

The alcohol hangover has been known since Biblical times: "Woe unto them that rise up early in the morning, that they may follow strong drink" (Isaiah 5:11).

Approximately 75 percent of those who drink alcohol to intoxication will experience a hangover. Consumption of relatively large amounts of alcohol leads to more severe symptoms, which include headache, nausea, vomiting, thirst and dryness of mouth, tremors, dizziness, fatigue and muscle cramps. Often there is an accompanying slump in occupational, cognitive or visual-spatial skills. Other symptoms, such as tachycardia (rapid heartbeat) and changes in blood pressure, might go unnoticed by the sufferer.

Although still under debate, the cause and mechanism of a hangover seem to involve several factors. Hangover has been suggested to be an early stage of alcohol withdrawal. Acetaldehyde, a breakdown product of alcohol metabolism, plays a role in producing hangover symptoms. Chemicals formed during alcohol processing and maturation known as congeners increase the frequency and severity of hangover. Liquors such as brandy, wine, tequila, whiskey and other dark liquors containing congeners tend to produce severe hangovers, whereas clear liquors (such as white rum, vodka, and gin) cause hangovers less frequently. Researchers have shown that severe hangover occurred in 33 percent of subjects who ingested bourbon (which is high in congeners) but in only 3 percent of those who consumed the same dose of vodka (which is low in congeners). As a rule of thumb, the darker a liquor's color, the more congeners it contains.

Patients with hangovers show changes in the blood levels of several hormones, which are often responsible for some of the hangover symptoms. For example, alcohol inhibits antidiuretic hormone, which leads to excessive urination and dehydration. Dehydration accentuates the symptoms of a hangover. Other factors that contribute to an alcohol hangover include consumption of larger quantities of alcohol than the person can tolerate. Individuals who drink alcohol rapidly, or without food, or without diluting it with nonalcoholic beverages, are more prone to developing a hangover. Mixing different alcoholic drinks can also cause a hangover. Additionally, smoking, loud music, flashing lights and decreased quality and quantity of sleep can exacerbate hangover headaches.

One can diminish the severity of the hangover by paying attention to the amount and type of alcohol consumed, as well as controlling other factors mentioned above. It is not clear that sugar-containing foods ease hangover symptoms, but sugar and fluids can help overcome hypoglycemia and dehydration, and antacids can help alleviate nausea. To reduce headache, anti-inflammatory drugs should be used cautiously. Aspirin may irritate the stomach and alcohol can amplify the toxic effects of acetaminophen on the liver. Other drugs have been used to treat hangovers, but most have questionable value. Propranolol, a beta blocker drug, has no beneficial effect on the symptoms of hangover. Tolfenamic acid, a prostaglandin inhibitor, produces some improvement in hangover symptoms when given prophylactically. The psychotropic sedative chlormethiazole has been reported to reduce symptoms of hangover, as have vitamin B6 and an herbal preparation called Liv.52 made by the Himalaya Drug Co. in Bombay, India.