With me, I only react to some foods when I eat them, and with others, just being around them makes me itch. My mom keeps strawberries in the house with little trouble. Tree nuts (almonds and such) also tend to not be as bad. I'm actually not allergic to hazelnuts.

Let's just say there was some irresponsibility on my part one day that thankfully had no repercussions.
I discovered one day that I cannot be around peanuts anymore after an open jar of peanut butter caused my tongue to swell up and eyes to itch. My brother likes peanut butter and jelly sandwiches for school lunches, so my mom buys the Uncrustables so that they're closed until he gets them to school. My dad likes Reeses Peanut butter cups, so he keeps them in his desk in his office, where I very rarely go.
Pineapple is my worst allergy. Trace amounts will cause me to react. I can only buy certain kinds of salsa because there can be cross contamination in the factories with some of them that contain pineapple. When I was a sophomore in high school, I ate salsa. I thought it would be fine. It wasn't. My throat started to close up. Thankfully, Benadryl took care of it that time. I went to see my allergist right after that and he asked me, "Do you carry an epi pen?" At the time, I did not, and he said, "You do now." If you cut a pineapple while I'm in the room, I can tell. My mom likes pineapple, so she buys it every now and then. She cuts it, puts it in an airtight container, and eats it when I'm not home. She also has to thoroughly was the cutting board and wipe down the counter tops around it. She does not buy pineapple very often because it is a gigantic pain for her.
My actual reaction is interesting. I accidentally ate peanuts one day in high school when my mom
tried to poison me accidentally put peanut butter on my sandwich instead of soy nut butter. I broke out into hives all the way up both arms, my tongue swelled up pretty badly, and I had asthma symptoms. This was freshman year of high school when the allergy wasn't as bad; I'd hate to think what it would be like now. My throat will also start to close up, which is when I would need the epi pen. I also tend to get a metallic taste in my mouth, which is a warning sign for me. One time, I accidentally put something in my mouth that contained almonds. I knew before I even swallowed, and I spit it out, washed out my mouth, and took a Benadryl. Thank goodness for the warning sign.