Should you be concerned about a red blister in the inside of the bottom lip of a child if he was born with it and the doctor keeps saying it will go away but it hasn't and what could it be?

It's hard to say what it could be but if your child isn't in any discomfort then i would try not to worry too much, easier said than done i know. If it grows in size or changes in any way or your child is in discomfort i would see your gp again