As many of the old timers here know, dd did OIT many years ago for peanuts and has been doing great. She has, however, developed some nut allergies over the years. Pecans and walnuts give her a stomach ache that the allergist said was most like a contact reaction much the way pollen irritates some people's airways/sinuses.
Last year, for reasons known only to teenagers, she decided to eat a whole cashew for the first time ever at school. She got the stomach ache, but advanced to itchy throat, rash, swollen face, and I used her epipen for the first time on her. She immediately felt better, and I sent her and dh to the ER to get monitored, steroids, etc.
A year later she's now in college. She had a Nutella crepe at a cafe, which turned out to be homemade "nutella" of basically hazelnut paste and chocolate. She's had actual Nutella in the past without a problem. She then walked in the heat across her very large campus. By the time she got to her dorm she knew she was having a reaction. She epi-ed herself, had her roommate drive her to her big sisters' apartment, and they all went to an urgent care. She's fine, and is spending the night with them.
I'm quite proud of her for handling it the way she did and I'm actually really glad she had that reaction last year. It took all the unknown out of the symptoms, the epi-pen, and what to do afterwards.
Learning points however - dd did NOT have a copy of our insurance card. Her sister did, but I dropped the ball on that one. And they went to 2 different places before finding an appropriate treatment center (school clinic is closed on the weekend and the next was only a coronavirus testing center.) We should have identified something ahead of time.
She's fine now but has decided all nuts are off limits from now own.