I am 30 with SW CAH.  I got chicken pox twice; once as a kid and once as an adult.  Once the herpes varicella virus is in the system it never goes away.  It can lay dormant and then flair up.  I have had shingles as well as severe outbreaks of fever blisters in my nose and ear.  I don't know if the CAH has anything to do with it or not.  I hope your son gets over it quickly and that it never returns.  Best of Luck!