I dont know the exact chemical effect it has,but it depresses the nervous system,slowing you down,and you dont feel pain as much.a hangover is your organs working overtime to detox.the blood goes from your head to your organs to help the process leaving you in a weakened state.Your nervous system is trying to function normally again.hangovers can range in symptoms from a mild headache to a massive psychotic episode of delorium tremors,the worst hell on earth imaginable.95%of mental health institutes deal with alcohol abusers here in Ireland.So watch out for the booze!!!!Actually,4 pints of guinness is a modest amount,and sounds like a good plan for me this evening,especially if there is sport on the tv.Cheers guys!