Another Day, another issue

Most recent issue for which I have no answer: Hyperactive Gag reflex.
The first recent occurence was 2 days ago. We had a play group over including 7 additional children and 2 moms. Caden noticed a baby sucking on a wooden block. Then it was set down in his sight, he started gagging, and then threw up in a corner of the kitchen. I found him still gagging and put him out on the patio until he could get under control. Really.
Tonight: a sour taste was left in his mouth after having chewed his vitamin. He started gagging, and threw up in the sink. I admit I smacked his bottom while this was happening tonight. It just seems ridiculous. Any ideas?