Hmmm... Talk to a few vets about his first, but it might be acid reflex, or bad heart burn, or whatever its called... But talk to a vet & see if you can give him either Pepto Bismal (Max was on that daily when he became allergic to his foods)... Also ask about tums... Now I have NO idea if a dog can have tums or not.. could even be deadly for all I know, so PLEASE talk to his vet first..

But thats just what I think it could be.