A hangover /ˈhæŋoʊvə/ (medical terminology: veisalgia from Norwegian: kveis, discomfort following overindulgence, and Greek: αλγία algia, pain) is the experience of various unpleasant physiological and psychological effects following consumption of ethanol, which can last for more than 24 hours. Typical symptoms of a hangover may include headache, drowsiness, concentration problems, dry mouth, dizziness, fatigue, gastrointestinal distress, absence of hunger, sweating, nausea, hyper-excitability 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 also play an important role. The symptoms occur typically after the intoxicating effect of the alcohol begins to wear off, generally the morning after a night of heavy drinking.Though many possible remedies have been suggested, there is no compelling evidence to suggest that any are effective for preventing or treating alcohol hangover. Avoiding alcohol or drinking in moderation are the most effective ways to avoid a hangover.The socioeconomic consequences and health risks of alcohol hangover include workplace absenteeism, impaired job performance, reduced productivity and poor academic achievement. A hangover may also compromise potentially dangerous daily activities such as driving a car or operating heavy machinery.