In addition to the discomfort, teething stimulates saliva production (by increasing histamine), he may not be drooling but he could be dealing with a lot more spit, and when he eats, even more saliva is created and it could all be too much lol.
Also if it is painful, he may not be chewing as well, and swallowing a bigger, less chewed bolus of food, could cause gagging.
