I've ran into this a few times. When I wear diapers, no rash happens but when I wear underwear too much, it starts to develop. I don't know if it is because I use diaper cream too much or what. I sweat a lot and I guess that could be part of it. Once I go back to diapers and cream for a day or two, it goes away. I just find it funny that I need diapers to do away with diaper rash.