Most diaper rashes respond to 3 days of warm water cleansing and air exposure. If you've tried this or the rash is bright red, suspect a yeast infection. Buy an anti-yeast cream (such as Lotrimin.) No prescription is needed. Dec 16, - However, in cases that have progressed babies can be very In addition to using an anti-fungal cream such as Lotrimin AF, there are other steps you And by following the other prevention and treatment tips above, you can.