NTA.
I'm legit a diagnosed celiac, can't eat gluten without it literally scarring my intestines / messing up how my body digests ALL food. I always either warn about that (all my close friends know but every time we go out for dinner somewhere I remind them to pick a place with gluten free options, aside from that idrc where we eat lmao) If it's a gathering in someone's house I usually warn whoevers hosting or ask them if it's cool to bring my own food (tbh I understand buying seperate ingredients and cooking it separately is a ballache).

If you have a legit allergy, its on YOU to organise yourself / warn others about it if you want them to accomodate.