Take her to the doctor and he/she will probably prescribe a prescription ointment, as your daughter probably has an infection as someone else suggested, since the rash is so persistent. This happened to my daughter when she was a baby. After treating her with the prescription ointment, I only ever put Vaseline on her bottom - no Desitin and especially no powder - and the bad rashes stopped. And always make sure baby's bottom is very dry before putting on the Vaseline - pat it gently with toilet paper if necessary. BTW, the Vaseline trick was also recommended by the doc.