Whenever our young children develop diarrhoea we are advised by the surgery to give them Dioralyte, to prevent them from getting dehydrated. This contains sodium chloride (salt), potassium chloride (similar to salt), glucose (sugar) and disodium hydrogen citrate. Would it not be just as good to use water with a bit of salt and sugar in it? What about plain water?

Dr Fred Kavalier answers your health questions

Dioralyte is the brand name of a powder that contains, as you say, essentially sugar and salt. The non-brand name is ORS, or oral rehydration salts. When a child has diarrhoea and vomiting, the greatest risk to their health is dehydration. ORS dissolved in water is an ideal fluid to prevent dehydration. Its combination of sugar and salts is more readily absorbed in the stomach than plain water. I wouldn't recommend you make up your own version of ORS. Too much salt can be dangerous and even fatal. It would be safe, however, to add a couple of level teaspoons of ordinary sugar (sucrose) to about 250ml of water.

Please send your questions and suggestions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax 020-7005 2182 or email to health@independent.co.uk. Dr Kavalier regrets he is unable to respond personally to questions.