A few hours In the sun? Destroy all the organs!
Eat some carbs? A real shame if those nerve sheaths got eaten...
Avoiding triggers becomes your life.
Both then and now, as some of her allergies are starting to fade, the trick was limited experimentation. Get to a known good state. Spend a week exposing yourself to small, then medium amounts of whatever you want to test. Observe your reaction. Repeat for something different the next week. You can test removing stuff from your diet this way too, but it's hard to identify false negatives: "I didn't get better -- does that mean I'm not allergic to this food, or that there are more triggers I still need to remove?"
It's basically the scientific method: form a hypothesis, establish a control, make a modification, observe results. It takes a lot of patience, but if your condition has a big enough impact on your life, is probably worth it. The hardest part is probably getting to a known good state. My friend was able to take an allergy test and err on the side of eliminating foods, to help her get there faster. I don't know what might help you; I'd recommend making a plan with your doctor.
It’s so random finding out that popcorn activates cold sores, pizza without a large (high pH) salad causes indigestion, etc.
An elimination diet is critical to under standing ones sensitivities.
I once spent a month eating nothing but sweet potatoes . Best I ever felt. Afterwards I could quickly tell what was an issue. Which was most everything not on strict AIP diet.
The Auto immune protocol diet is an excellent place to start. Focuses on inflammation.