Stephanie Stepford told me about this one!
For the worst diaper rashes (even those caused by yeast) use a mix of equal parts liquid Maalox and Aquaphor or A&D on your baby each time you change a diaper. It is best to either air dry or dry with a soft cloth before application so that no moisture gets trapped underneath the paste.
The Maalox soothes irritation and feels cool upon application. It will reduce the acidity of the urine and stool it comes into contact with, while the Aquaphor or A&D cream will help create a barrier between the skin and urine.