What Causes Red Rash Around Mouth In An Infant?

My 20 month old has had a red rash around her mouth for the past couple of months. She s been to 3 different pediatricians and gotten 3 different recommendations. One said it was impetigo and gave her a topical antibiotic. Turned out not to be impetigo and the antibiotic ointment didn t help. The second one said it was just from a runny nose and saliva from having her hands in her mouth ( she s cutting back molars). She said use hydrocortisone but in limited amts. That helped for awhile but doesn t seem to be effective anymore. The 3rd pediatrician said it was perioral dermatitis from having her hands in her mouth but said to use some type of barrier to seal out wetness. We ve been using Vaseline but haven t noticed any improvement. I almost feel like it s getting worse. Any other thoughts on this and what to do?? It does seem to be consistent with things I ve read about perioral dermatitis. It looks awful