When my son had this a couple of years ago the pediatrician told us to take maalox or mylanta and squirt it in his mouth (he was only one at the time). He said it would coat the sores to help him with the pain enough so he could eat. This is only short term, since saliva washes it away, but your son is old enough to swish and spit, so he should be able to do it frequently if it helps him. How long it takes to clear up depends on how severe it is. My son's was only painful for about 6 days, but two years later my daughter ended up with it and then gave it to me, and we were both in very rough shape for almost a full two weeks. Just a note, those sores hurt so bad, offer him anything he wants to eat. My daughter lived on drinkable yogurt through a straw and applesauce and bananas for two weeks. For me, it didn't affect my appetite and I was starving, but couldn't eat anything for almost 2 weeks without incredible pain. (It feels like you are trying to swallow razor blades). We kept offering popsicles to keep her hydrated which seemed to help numb some of the pain for her too. I used some numbing wand that I found at target for the pain, but I can't remember the brand and I know I tossed it since it was loaded with germs. It may have been Canka. I don't know what the age recommendations on it are, but you may want to look into that. I used that at night before going to bed so I could relax enough to fall asleep. Just take your cues from your son, we just took it real easy with both my kids when we had this. Beware though that it is highly contagious so frequent hand washing is a must, and also that he will continue to excrete the virus in his bowels for a long time, so proper hygiene after using the potty is very important. Good luck.
