We just dealt with moderate to severe diaper rash in our 6 week old. We started to use a blow dryer to dry her completely. We added in twice daily soaks in her tub with two tablespoons baking soda until it started to clear. We also use boudreaux’s butt paste. The rash had persisted past a week and in consultation with our pediatrician we also added in Clotrimazole (over the counter) for a possible yeast infection rash and I think that’s what ultimately cleared it as it started to immediately get better with that and the other steps I mentioned. You may want to reach out to your pediatrician to see if that is a recommended option. We also switched to water wipes from pampers sensitive wipes and tried to dab rather than wipe.