[Peach_Bums_Mum]

You can strip wash the nappy with some dishwashing detergent and hot water, then rinse rinse rinse. That should get it off.
There are other things you can use instead of thick zinc type creams which work effectivley and are better for use with MCN, like paw paw or calendula ointments. I also use Curash baby powder regularly without any hassle. Perhaps you could also try just using a natural fabric against his skin, and changing really often, wiping with a natural cleanser at every change.
Goodluck