Can you be allergic to an accumulation of multiple things, but not allergic to the things separately?

Bear with me, this may be long as I want to give sufficient background info --

31F. I've always had sensitive skin / psoriasis/ eczema and mild allergies, but never severe or never to any foods. Just a mild reaction that's easily treated with 1 dose of OTC meds as needed.

For instance, it's not uncommon for me to wake up to random itchy patches of skin on my neck, or my arms, or my leg. No particular trigger. It'll resolve on its own that day or a day later.

Occasionally, when I shower with hot water, or sweat a lot during a workout, sometimes my skin will be bright red for hours after but then it'll go away on its own.

Every few months I randomly break out in sneezing fits for 30 mins with no particular trigger, but then it'll go away.

I am more allergic than the average person to dust: If i have a hoodie in the back of a closet that I haven't worn for over a month, I need to wash it before wearing it or else my skin will itch and I'll sneeze/ have extreme watery eyes.

In childhood, I would get itchy arms from eating chocolate, yet I continued eating it and eventually grew out of that allergy -- have been eating chocolate my whole life.

I've had Epipens on hand my whole adult life but luckily never need

So NOW. fast forward.

In October, I ate a date with peanut butter. 2 foods i've been eating for years, and the packages were not new (opened and had been eating from them for at least a few weeks). About 10 mins later my face got extremely hot, bright red, and everything started swelling (lips, tongue, hands etc) as the redness quickly spread to my neck/ arms/ chest. From beginning of the reaction to it being full blown/ severe, only like 7-10 mins passed; it was scary how quickly it happened. 911 came and administered Epi and took me to ER.

In January, I ate cooked sweet potato/ broccoli/ salmon, also 3 foods i've been eating my whole life, and same thing happened. 911 came and administered Epi this time too.

A few weeks ago, I ate chia pudding that had chia, peanuts, blueberries. 3 more things that I eat alllll the time, in fact, I ate the same meal from the same batch 2 days prior. I had a similar but not as severe reaction this time -- my face started turning red but I took a double dose of benadryl and it went away within the hour, no Epi needed.

NOW. Here's the important part: I've tried ALL THESE FOODS AGAIN at home with my mother (she's a nurse) and my Epipen next to me, with no reaction! Multiple times for each food. I eat peanuts / peanut butter all the time with no reaction. Even today, 6 hours ago.

I was trying to figure out what else it could possibly be, what all these instances have in common is that it was my first meal of the day, with which I take my womens' multivitamins/ vitamin D supplement. So I started thinking I could be reacting to something in the vitamins or Vit D, but again, these are opened bottles that I've been taking for months with no issue. SO THEN I did the same type of test. I took the multivitamins multiple times with my mother/ epipen next to me, no reaction.

So could it be that over many days in a row, something in the multivitamin accumulates and causes this reaction? i.e. a one off dose of them is fine, but a build up in my body is causing this? OR could it be that I'm mildly allergic (no reaction) to multiple things, but consuming these together is causing this?

Obviously I am going to get proper allergy testing -- it's taking a while because of insurance issues. BUT wondering if anyone has any insight/ theories as to what's happening? it's so scary to go through life not knowing what's ok to consume and what's not..