A hangover is the experience of various unpleasant physiological and psychological effects usually following the consumption of alcohol, such as wine, beer, and liquor. Hangovers can last for several hours or for more than 24 hours. Typical symptoms of a hangover may include headache, drowsiness, concentration problems, dry mouth, dizziness, fatigue, gastrointestinal distress (e.g., vomiting, diarrhea), absence of hunger, light sensitivity, depression, sweating, nausea, hyper-excitability, irritability, and anxiety. While the causes of a hangover are still poorly understood, several factors are known to be involved including acetaldehyde accumulation, changes in the immune system and glucose metabolism, dehydration, metabolic acidosis, disturbed prostaglandin synthesis, increased cardiac output, vasodilation, sleep deprivation, and malnutrition. Beverage-specific effects of additives or by-products such as congeners in alcoholic beverages also play an important role. The symptoms usually occur after the intoxicating effect of the alcohol begins to wear off, generally the morning after a night of heavy drinking. Though many possible remedies and folk cures have been suggested, there is no compelling evidence to suggest that any are effective for preventing or treating hangovers. Avoiding alcohol or drinking in moderation are the most effective ways to avoid a hangover. The socioeconomic consequences of hangovers include workplace absenteeism, impaired job performance, reduced productivity and poor academic achievement. A hangover may also impair performance during potentially dangerous daily activities such as driving a car or operating heavy machinery. Signs and symptoms An alcohol hangover is associated with a variety of symptoms that may include drowsiness, headache, concentration problems, dry mouth, dizziness, gastrointestinal complaints, fatigue, sweating, nausea, hyper-excitability, anxiety, and a feeling of general discomfort that may last more than 24 hours. Alcohol hangover symptoms develop when blood alcohol concentration falls considerably and peak when it returns to almost zero. Hangover symptoms validated in controlled studies include general malaise, thirst, headache, feeling dizzy or faint, tiredness, loss of appetite, nausea, stomach ache, and feeling as though one's heart is racing. Some symptoms such as changes in sleep pattern and gastrointestinal distress are attributed to direct effects of the alcohol intoxication, or withdrawal symptoms. Drowsiness and impaired cognitive function are the two dominant features of alcohol hangover. Causes The processes which lead to hangovers are still poorly understood. Several pathophysiological changes may give rise to the alcohol hangover including increased levels of acetaldehyde, hormonal alterations of the cytokine pathways and decrease of the availability of glucose. Additional associated phenomena are dehydration,