My 2 yr old has a rash

My 2 year old daughter has a rash in her armpits.  She does not have particularly sensitive skin.  I noticed that she got the rash after wearing a turtle neck that haad been packed away for a while. Initially it looked like poison oak/ivy, but she hasnt been outside.  Now it looks closest to ringworm but it is under both arms and appears lightly on her neck.  I had some left over anti-fungal cream from when my son had ringworm more than a year ago.  I applied it and it appears to by drying up mut not getting any smaller.  She says it does not itch or burn so I don't know what to think.  It looks painful but she is not bothered by it at all.  Any suggestiions?