That's very interesting. I have read that allergies can cause a 'chest heaviness' which may be what you are experiencing. Obviously a quick bout of chest inflammation might cause this (an allergic reaction)? I would guess this is part of your allergic reaction, obviously, and I think a fair number of people have it. Doctors just don't know why. But I'm sure it's scary to have chest pain. They've done a full work up to make sure it is nothing coronary related or anything like gerd?
Could it be milder anaphylactic symptoms. I had a severe allergic reaction to an unusual apple pip that had got ground into a pre-made juice drink at a bar/restaurant. I get cold and pollution related urticaria, but this time developed very severe hives and became really burning hot all over. I had difficulty breathing and the paramedics said it was anaphylactic shock. Fortunately, I'd quickly taken some anti-histamines that helped to alleviate it. I remember having chest pain, though that could have been due to panic or constriction.