When Leyla had nappy rash after being in sposies for the weekend, I would put the nappy cream on towards the end of nappy off time and leave it to be absorbed before putting a nappy with a fleece liner in it on her. If you put the nappy straight on and the nappy (cloth or disposable) absorbs some of it, not as much of it is going where you want it - in LO's skin. Also, and this is entirely unscientific, I always use a microfibre nappy when we're using bum cream. For some reason I have it in my head that any cream that does get in it will wash out easier than natural fibres, I probably think that because they use microfibre for cleaning cloths. Not sure if it's true though.