E.M.
I use the clear Lanisoh cream on my eczema while I am breastfeeding, since it is baby-safe, and it works really well. As soon as she gets out of the bath, towel her bum and then put on a heavy coat of the Lanisoh and then the cotton undies. In addition to irritation from an allergen, eczema can be caused by friction, so maybe the looser fabric of the undies is rubbing on her skin, where the diaper stays in place more?? A layer of goop between skin and fabric could help there.