Poor little guy.

Have you talked to his doctor about whether he's at a safe age for any of the antiviral drugs? If he is able to go on a preventive, daily dosage at times when you know he's likely to get an OB, it might either prevent it entirely or at least make it milder and heal faster. Just a thought.
There are also some alternative remedies out there you might want to try, but I'd be careful about them because of his age. His system is likely to be more sensitive to things and I doubt much is known that's concrete about alternative remdies regarding age considerations. A qualified naturopath with a thriving full-family practice might be able to advise you about that based on their training and experience.
Good luck!
TheOneInFour