I would say coxsackie also. My son had it around this age. He had the blisters all over the inside of his mouth and tongue, but it started with just some red spots and cold symptoms. If tis turns out to be the case-be prepared it will get worse and is very painful. The only thhing that got my son to eat anything was this- my doc told me to mix benadryl and maalox in a cup, stir it together then try to coat the inside of the baby's mouth-I used latex gloves and my finger- it wasn't easy and he screamed but aftet he numb enough to eat (he hadn't eaten in 3 days) This doesn't last very long so have whatever you're going to feed him ready before you do this. Good luck!