Hi shroom.
I looked on the internet for the best description of my symptoms and found it under the name of mastocystosis--a disease caused by the proliferation of mast cells (producing and releasing histamin in the bloodstream)-hence the multiple allergies.
This proliferation of mast cells is said to occur as a result of the presence of an infectious agent in the intestine: parasite, worms, etc.
This fits my case to a tee since my allergy problems started during a trip to Mexico and very likely following a multiparasitic infection contracted there.