The issue is more complicated than so far described. We don't have "a" immune system, we have multiple ones. There are B-cells, t-cells, glial cells, and probably others. Normal allergies involve one system, viral infections another, cell damage might involve several. My ME seems to involve t-cells and glial cells, and isn't affected by type I allergies. For others, it may be different. The different immune systems do interact somewhat, so t-cell activation will also activate glial cells (warning them that an intruder might be trying to cross the BBB). I'm not sure of the interactions between t-cells and type I allergies.
For the question of whether I had immune system problems before ME, I seemed to have a strong t-cell system (didn't get viral infections often, and they ended quickly) and no type I allergies. I did, in retrospect, have what seemed to be a very slight but consistent type IV reaction to oranges. Then one day that slight reaction triggered what seemed like full-blown flu symptoms and type IV reaction to most foods. I managed to stop the type IV reaction after 2.5 years, but the symptoms remained, triggering only 20 minutes after eating (probably involving cerebral tryptophan metabolism). Eventually I figured out that it was ME. I can say that my ME symptoms were mostly identical to those from type IV sensitivity, which seem to involve kynurenines.