In 'the old days', we were told to take salt tablets in tropical climates. Does this advice still hold true?

Dr Jules Eden replies: Not really. Things have moved on since then. Salt tablets had their place for those suffering fluid loss, either through excessive sweat or diarrhoea. Sodium acts osmotically to retain fluid in the body, so keeping it hydrated. But there are better salts on the market, such as Dioralyte which also replaces potassium and glucose. And it comes in different flavours, rather than simply tasting 'salty'.

I'm going on an all-inclusive holiday, but I'm not looking forward to the hangovers. Any advice?

If the only certainty in life is death, then a hangover is the best way to face those certainties early on. The problem with too much alcohol is that it hits the body in many ways. Alcohol itself is a toxin; when the liver's enzymes are saturated and can't take any more, it flows merrily around the blood stream causing stupid behaviour and a headache. The headache is also compounded the next day by the dehydration and low blood sugar that the excess booze causes. Alcohol inhibits a hormone called ADH. Block this and you pee too much, hence the dehydration.

Over-indulging can push you into the wrong pattern of sleep, too. We need both slow-wave sleep and rapid eye movement sleep. The latter doesn't really occur in drunken sleep, so you lack deep dream sleep and wake up knackered.

So you see how toxins, dehydration, low sugar and tiredness can make you feel so bad.

Now for prevention and the cure: before the big night, hydrate as much as possible. Milk is my favourite. During the night, stick to one sort of drink, don't mix. Before going to bed, drink at least a pint of rehydration salts, such as Dioralyte, that sugar load you. And in the morning, sleep as long as possible.

There is an easier way ... Don't drink, but where's the fun in that!

· If you have any questions you want top ask Dr Jules Eden, email travel.doctor@theguardian.com, or write to The Flying Doctor, The Guardian, 119 Farringdon Road, London EC1 3ER.