Dr. Greene's Answer
Any diaper rash that’s been going on for more than a week has most likely become complicated by a yeast infection. This is especially common when the rash is exacerbated by loose stools.
The best course of treatment is to keep the area as clean as possible. You might want to consider bathing your baby’s bottom with warm water after each diaper change rather than wiping already tender tissue with a wipe. After cleansing, apply a moisture barrier ointment such as A+D to aid in healing the damaged skin, along with an over-the-counter yeast treatment such as Lotrimin to combat the yeast. If the rash worsens or doesn’t show improvement after a few days, you’ll want to check with your baby’s doctor.