My gosh, Porcelain Interior...sounds like you've been through quite a lot!!! I'm glad you've identified the culprits and are able to avoid the dangers.
I've heard, as Carroll says, that in some cases, either some food intolerances can lead to allergies, or other intolerances, and possibly some allergies can lead to more allergies...etc. A real snowball effect and can get very involved and puzzling.
My hunch is ANY intolerance leads to leaky gut, and then leaky gut messes with your immune system enough to create further allergies...because your immune system is on alert for viruses and gets confused as to what is friend and what is foe...either reacting violently to things like pollen, or even starting to react to the body's own tissue, as in autoimmune disorders. Leaky gut...another groundhog(g) hunch, for whatever good they are

, might possibly be involved somehow with the general oogies that people call candida...I'm all fuzzy about that...whether in fact it can really exist, etc., but I do think normal body flora can be thrown wacky and all sorts of things go wrong when all these immunity confusions are in place...and so, I would personally (as a non-scientist groundhog) catagorize candida as an aspect of leaky gut syndrome in general. Just musings, though...i don't think anybody, even researchers, doctors and scientists, really understands WHY people or other creatures have allergies or intolerances.
Those with intolerance/allergy might feel unlucky somtimes...but really, at least KNOWING which things cause the symptoms is really a pretty lucky thing, giving one the power to be proactive enough to avoid problems.
I think I've read that at least with some forms of contact allergens, the more time the person can avoid the allergen, the better the body becomes at coping with some possible future exposures. If that's true, that's good news for evnybody with allergies. That could possibly extend to intolerances as well, as I've heard that celiacs are extremely sensitive the first few years gluten free, but then as time goes on and they remain away from gluten, accidental exposure begins to produce less severe symptoms. These are just things I've heard...I hope they are true!