JOJA, I don't think that there is anything else you can try. The only thing I might suggest is the obvious trying to keep it as dry as possible and when he goes down at night put a really thick layer of something like Bepanthen (sp) on it. You can get that from a chemist or even at Woolies I think. Anything that creates a barrier, treat it just like a bum rash, dry and protected. HTH

Take care
Trish