I'm getting increasingly worried about DS's allergies. He's 2 years old; we've initiated testing and will be getting his blood test results on Friday, but he had another somewhat severe reaction two nights ago where his face and neck started swelling up and his eyes were itching so bad he kept clawing at them and it was awful. We gave him benedryl and it subsided enough to not go to the ER, but I'm wondering how concerned I should be about this. Do anaphylactic shock type allergies develop over time, or are they pretty set to begin with? Does this sound like something that could be a precursor to anaphylactic reactions?
I'm a little scared about this because I suspect that the trigger is ingested fungal proteins, and that's going to be tough to completely avoid. (He's broken out in blistery hives from eating a small piece of mushroom, had a positive IgE result for yeast, and our two really bad and scary reactions were first to Houston's digestive enzymes and most recently to a melatonin formulation, which I have now researched as sometimes being fungally derived in commercial synthetic supplements.)

I think some anaphylactic reactions just start and some happen over time. DS's happen over time. As an infant, he didn't resond anaphylactically to me eating dairy, he just got eczema. At 9 months, we gave him one piece of shredded cheese and he got hoarse like he needed to clear his throat. Fast forward a few months, he was eating green beans at Cracker Barrel that were supposed to be dairy free and he broke out into blotchy hives on his face, chest and upper arms and was having difficulty breathing. I think every person with FA should carry two epi pens with them at all times. Ana reactions can happen unexpectedly.