MRC is right.
There are full write ups on the fuels, on the techniques (including wiping the face

) and all of that in this site.
Some of it is in the link that aston put up. Doc has an interesting story on pg 3(or so) on that link of someone who was suffering severe ARDS from
Fire Breathing with alcohol.
It also links to what causes ARDS.
And it all goes back to, it's not what you swallow, it's what you inhale.
Sure you *can* swallow oils, starches, alcohol but the fact remains the body isn't made to inhale them. And we do, we will, when
Fire Breathing. We simply can't create a cloud and not breathe any of it in.