Hello-
Your son would seem to have an unfortunate combination of incompetent lower esophageal sphincter, for which he is being treated, and a very strong gag reflex. The combination would be almost guaranteed to produce the result of
vomiting with laughter or
coughing. So long as this is the primary way this result is triggered, there's probably no great danger of aspiration (which could cause a lung infection). Just be sure he gets his medication regularly. The tendency to
vomit should moderate over time. The reflux problem will probably require some sort of care for a long time, although sometimes this, too, can resolve or at least go into remission.
I hope this is helpful.
