This was always my fear when DS was younger.
https://longisland.news12.com/i-never-felt-so-close-to-death-dix-hills-student-suffering-allergic-reaction-says-school-officials-assumed-she-was-on-drugs (https://longisland.news12.com/i-never-felt-so-close-to-death-dix-hills-student-suffering-allergic-reaction-says-school-officials-assumed-she-was-on-drugs)
When I had my worst anaphylactic reaction, I was walking through a mall. No hives, no visible swelling. Another parent from my kids school saw me, and told everyone at the school (staff and other parents) that I had been high on something when she saw me.
So, it doesn't surprise me at all that someone would make that assumption with a teen.
This is why I told DS to always wear his MedicAlert - because if someone sees a teen vomiting, out of it, etc., they are going to think intoxicated, not anaphylactics.