Sometimes after a ride I get excruciating pain in my mouth when I try to eat. I'm pretty sure this is the same thing as @
kingston describes --he and I have discussed this before.
It generally happens after a ride that didn't go so well, as compared to a ride that went well. By 'didn't go so well' I mean I was getting weak toward the end, probably didn't eat/drink right during the ride. Even so, I can usually keep eating something throughout the ride. I'll be feeling okay at the end of the ride, snack on something on the way home, finally settle down to dinner, and the first bite of food sends pain shooting through my mouth. I believe it's the salivary glands that have for some reason shut down and getting them to restart is, well, painful. It may take a few bites of food before this goes away, but usually I'm able to finish my meal, though it leaves the whole inside of my mouth very tender (and makes me a bit wary of food). A couple times it has also happened the next morning, after a ride.
Recently this has happened to me a few times when i haven't been riding. That is perhaps even scarier, because if I've just been riding I know I can blame the riding.