Due to a series of Christmas cock-ups, confusion between cups etc., we ended up putting a half-drunk cup of milk back in the fridge and using it the next day instead of the fresh one I'd prepared. So DS sucked on the cup (one with a rubbery teat and valve), drank half the milk, it went back in the fridge and he had the same one 24 hours later. I know this is what you are always told NOT to do - sterilise teat, don't use again once started, throw out milk within an hour once started, etc etc. Bit worried about what the risks are and what I should be looking out for. He's gone to sleep and settled eventually though quite crotchety - but I'd expect that because it's been an unusual day, different routine etc.
He is 6mo and the teat was sterilised before the initial use. Can anyone advise (or please tell me I am being a paranoid 1st timer if that's all it is)?