Typically the bodies default response to everything, real of not, is inflammation. Which is the primary symptom of allergies. Which also happens to be the symptom most responsible for the popular diseases for which there is no rational/clear response for such a potentially dangerous over-reaction - other than unlucky genetics.

I was diagnosed with chronic heavy metal poisoning [0][1]. I had developed almst asthma-like pollen allergy after an event that very likely contributed quite a bit all at once. Over the years I also got allergic to cats. Everything is completely gone now after years of chelation. The creation of additional "outflow" surely must have helped get the stuff out from the system overwhelmed by amounts it could not handle using its normal methods.

A tiny bit of my story, pieces of it posted on several occasions:

[0] https://news.ycombinator.com/item?id=17310648 (in this thread, all my responses)

[1] http://onibasu.com/archives/fdc/137355.html and http://onibasu.com/archives/fdc/137356.html (list of things that improved/disappeared through chelation treatment) -- Psoriasis is missing from that list, that completely disappeared too, had it on both elbows since "forever"