Sometimes, gastroenteritis can cause a temporary lactose intolerance. It is for this reason that sometimes health professionals will advise that you stop giving children milk products. this doesn't include human milk as human milk is specifically designed for the gut and actually protects the gut from infections, whereas formula, cow's milk, and other dairy products do not.

If you are giving the child juice, it should be about one in six concetration. Otherwise get some gastrolyte powder from the chemist and make it up according to directions and give them this to drink. You shouldn't give them undiluted soft drink, although I have heard this recommended - it's too sugary and will make their gastro symptoms worse.

Once their symptoms are improving, you can re-introduce milk. Start by giving it half-strength - this is about the only time it's ever right to make your formula up against the directions on the can, if you use formula - and as long as this doesn't make their symptoms worse, you can then go to full-strength feeds.

After your child is better, if they will eat it, try giving them some yoghurt with live cultures in - acidophilus and bifidus. This will help re-establish the normal bacterial balance in their stomach, which will have been upset by the infection, and also by any antibiotics they may have had (on a side note, antibiotics are rarely any good for gastro, as it is usually a viral infection).