My 14 month old daughter has a really bad diaper rash. I don't know if she is having an allergic reaction to some new foods we've given her or if it's from her teething. But now she has developed open sores on her butt and cries every time we change her diaper. We have tried Desitin but that's not helping. We don't even have to try to let her run around naked cause once she pees, she takes her diaper off and runs around naked on her own. How do I know if it's a normal but obviously bad dipaer rash or a rash because of a food allergy or I've heard it could be yeast infection? How do I know what it is? And if there is anything else I can do for her until I can get her to her doctor. Please help!!Well she just got this diaper rash yesterday and my husband noticed the little open sores. She's gotten a rash like this before but we were able to get it gone within that same day. I'm at work right now so I can't take her to be seen for another hour or so and my husband is at home with her and has called and left a message for the on call doctor. Thanks for your advice so far! It will all be helpful for the future.