My son has blistery spots around his mouth and anus?

See doctor: Blisters or other sores around mouth and anus can be caused by several conditions. There are infections such as herpes viruses that can do this. Crohn's disease and chronic granulomatous disease can do this too. He should be seen by your pediatrician. If its not clearly an infection, then he should see a pediatric gastroenterologist. Either way, he needs to be evaluated asap.