When we vomit, what gas do we expel? What is the effect of stomach acid on your mouth?
Usually the gas we expel is just air...........
As to the stomach acid, you often notice that after you spill your guts the back of your throat and your mouth and tongue stings; this is the corrosive effect of the stomach acid. Of course you know how unpleasant this is.
They say that those people who suffer bulimia (i.e. binge eating followed by induced vomiting) usually have terrible teeth because of the effect of the acid on their teeth.