Heartburn, vomiting and burping (warning: TMI for emetophobes)

[PrettyCandles]

If heartburn is the pain you get when a bit of stomach acid escapes up the oesophagus, why doesn't vomiting burn in the same way? And why, when I have a particularly gross burp that brings up some stomach contents, does that not burn either? Do I have a Teflon oesophagus?

I know it's a disgusting question, but I am asking genuinely.

I burn when I burp but perhaps it's something to do with whether the stuff coming up is acidic or whether it's just gas with stuff that's not got acidic yet? (have no idea really!). I also burn when I vomit.