B.F.
I agree with Dawn that it could be foot n mouth, it is viral and will work its way out. The fever lasts for about 7-10 days and my oldest DD never got the blisters but it was long rough patch...keep pushing fluids, even popsicles, jello, whatever you can keep in him and do the alternating motrin (8 hrs) and tylenol (4hrs). Hang in there mom!