A hangover is basically your body's way of telling you off for overdoing it. The symptoms you experience are produced when your body tries to rid your system of toxins and process the alcohol. Symptoms such as headaches and malaise are mainly caused by dehydration. One of the best remedies is a sports drink like Pocari Sweat. Interspersing drinks of water between all the alcohol will also help.
Congeners are another culprit in hangover headaches.
Produced in the fermentation process, congeners are chemicals that produce pleasant flavors and smells in alcohol but have nasty results in your body. Choosing clear spirits with low concentrations of them helps to lessen their effect. Mixing drinks means your body has to identify and process different types of congeners and as a result it takes longer to flush them out. Coffee-addicts may also compound their headache if they don't have caffeine, but just make sure to drink plenty of other fluids too. The scientists are out on whether fructose really does free up oxidized B vitamins for the aldehyde dehydrogenase enzyme to use in breaking down alcohol.