Esophageal Inflammation. Damn, that's rough.
I don't have anything that causes anything that severe. I do, however, become intolerant of milk every once in a while. Dunno the biological source of it; If it was due to a lack of enzymes, I'd have thought I'd be permanently intolerant of it, but no, only every once in a while, usually after I've eaten too much sugar.
On the subject of medical problems, though, I've had this weird thing happen to me about six times in my life, when I've witness some sort of extreme body deformity or mutilation (e.g. that infamous toenail scene from Spongebob's "House Fancy") and I get a two-minute dizzy spell. Also, if I run afoul of some short-tempered authority figure, I get a fever.
Not exactly allergies, but I thought they might be interesting from a medical standpoint.