Thanks for all your replies.
We do the hand washing, eat really well with lots of raw fruit and veges etc but we seem to still be constantly sick.
I do believe it builds healthy immune systems in the long term but I think it's just having 4 young children that means by the time the last is better there is a new round. The last of them recovered last week and now we are starting a new cycle with a different bug!
I am exhausted caring for them all
Maybe I should start a thread on how to cope with that