Everything you always wanted to know about hangovers *

* but were too insensible to ask.

After the Millenium, the hangover. It may well be a foretaste of your own personal hell, but believe me, the symptoms will be the same all around the world. Tiredness, sickness, blood-streaked eyes, dry mouth and a sweaty, pale complexion. You awake feeling like death warmed-up, and then you solemnly promise yourself never to take another drink. That’s what's known as a hangover.

The best cure for a hangover is to avoid it by drinking in moderation. But who's going to drink in moderation on the eve of the Millenium? Even so, it's possible to take certain precautions which may reduce the next day’s agony. There are one or two remedies before going to bed (if you manage to get to bed) and one or two more for when you wake up in the morning. Applying a little science to the problem can help you feel and look a bit less like a moving corpse.

Every drink worthy of the name contains ethanol (ethyl alcohol, C2 H5 0H, if you remember your school chemistry) and this is the stuff that gets you drunk. Beer has about 3 to 5%; wine 8 to 14%; most spirits, 40%. These days it's easier to understand the alcoholic content of what you're about to drink because it'll be marked with the percentage of alcohol by volume. It's a whole lot easier than the old system of degrees proof, which was idiotically complicated. If you do have any bottles marked in the old way, you might like to know that 100 degrees proof spirit is 57% alcohol by volume. Why this is so has got to do with gunpowder, but there's no space here to go into that now. Ethanol makes the drinker drunk. It gets at those centres of the brain which affect balance and memory, it dilates the cerebral arteries and also the blood vessels beneath the skin. In addition, it depresses feelings of pain and fatigue and other areas of the brain which exercise caution over our actions - hence the widely held view that alcohol is a stimulant. It is not: it's a depressant. When the six-stone weakling picks a fight in the bar, it isn’t because he's stimulated by alcohol; it's because the part of his brain which would normally tell him not to be such a bloody fool, has been numbed into total silence.

Ethanol is a carbohydrate and a food, and as such is broken down in the body by a complicated metabolic process. Ethanol becomes acetaldehyde, then acetic acid and then carbon dioxide and water. This cycle (the Krebs cycle) is very delicate, and if it is upset, toxic acetaldehyde can remain in the system. Studies have shown that acetaldehyde is present in excess during the hangover period. Chief among the substances which can upset the Krebs cycle are chemicals called congenerics. Over 100 have been identified. They are by-products of fermentation and maturing processes and give the characteristic flavour to various drinks. Some drinks contain more congenerics than others, and here we may have the scientific origin of the widespread belief that certain drinks are more likely to leave you feeling ghastly.

My 'Book of Lists' gives a table of popular drinks in descending order of their percentage of congenerics. It goes like this: bourbon whiskey, malt Scotch whisky and rum, brandy, blended Scotch whisky, wine and gin, beer and vodka. Experiments in which willing volunteers drank to excess, showed that hangovers were at their worst after bourbon whiskey, followed by ordinary whiskies, brandy and rum, and least with spirits like vodka. It seems pretty conclusive: the more congenerics, the bigger the hangover.

So the first anti-hangover tip could be to drink only vodka at The Big Party. Second is the well-known full stomach philosophy. Anything bulky, fatty and oily tends to slow the rate at which alcohol gets into the bloodstream and gives it more time to be eliminated. The ancient Romans took a small glass of olive oil before a major Saturnalian orgy of drink, and they knew a thing or two about excess. Others swear by a glass of milk or a plate of mashed potatoes and butter. In Italy you can go to the chemist and buy 'Tiase' tablets, which replace your lost liver salts before you lose them. You take them when you know there's a night of drink ahead.There is not much more that can be done before drinking. The next part of the anti-hangover campaign starts after being dumped home in the small hours by the sullen, sober member of the party who was elected the designated driver.

You should now - God help you - go for a brisk walk around the block, breathing in lots of fresh air, but this is probably too much to ask. It would help to sober you up, stop the ceiling from slowly rotating after you've got into bed, plus the blast of oxygen will undoubtedly reduce the depth of the following morning’s hangover. You could try drinking lots and lots of cold water. Alcohol dehydrates the body and you might as well start putting the water back. Tablets of vitamin A and C are said to be beneficial, possibly because they aid the Krebs cycle of breaking down the acetaldehyde. Salt tablets also help some people. Whatever you do, don’t take sleeping pills. It says on the leaflet, 'after ingestion of alcohol, these tablets can produce prolonged and heavy sedation'. You might never wake up.

And so to bed. In the morning there's a small army of men with jack-hammers inside your skull. The pale winter sunshine is as bright as a supernova; the rustle of a newspaper is like the starting grid of a formula one race; the ringing of the telephone (wrong number) makes the roof rattle. All precautions have failed - you have a hangover. There are instant remedies by the dozen. Black coffee, a serious hit of carbohydrates, a beaten raw egg, Solpadeine, or for the stout of liver, another drink. That works, but you're just postponing the hangover. Kingsley Amis once recommended the vigorous performance of the sexual act, (he must have been joking). My own remedy is to sleep for as long as I can, family permitting. If it's a day off after the party I suggest you do the same. Time is the best healer - at least, until the next party.