D.B.
My 2 youngest kids got bad diaper rashes at that age when they started teething. I use Boudreaux's Butt Paste (found at Walgreens or other pharmacies) and corn starch baby powder(Gold Bond brand). I would also let them air out their bottoms between frequent diaper changes. The air helps to promote healing. It might not be a yeast infection so I'd get your doctor's advise. I also gave them a little bit of children's Motrin (ask your doctor how much) to reduce the inflammation. Don't worry, it will get better.