My just turned two-year-old seems to have quite a sensitive gag reflex, and often throws up if he coughs particularly hard (when he has a cold, nothing more serious). It's like he's got mucus stuck in the back of the throat and he just overdoes the cough sometimes and triggers his reflex. It doesn't seem to bother him but it scares the life out of me and is obviously not nice to clear up, especially at night in his bed! Is this quite a common thing? Will he grow out of it soon?