Consider visiting a paediatric dermatologist. My boy had this when he was a few months old. We went to the hospital and the doctor misdiagnosed and gave us cream for ringworm treatment. We went to a paediatric dermatologist and she told us that it was due to too much saliva lol. We went to Dr. HM Liew Skin Clinic. She’s really nice, friendly, knowledgeable and professional.