I'm so sorry for the food allergy scare. And so glad ds told you he wasn't feeling well and got the epi-pen in time. Be sure to get a replacement Rx epi-pen soon!
You may wish to coach ds to learn to say directly when he doesn't feel well, if it feels like his food allergy and ask for his epi-pen in case it is needed.
I've known kids with some different serious things and they all learned very young to say if it felt like {their known problem, with known action to be taken} or if it felt like something else. Lots of opportunity to discuss vocabulary for different body parts, pains (stabbing, throbbing, dull ache, swollen...) and ways in which those pains in those parts are limiting functioning.
Does he wear a medical dog-tag, medic-alert bracelet, or something similar to indicate his severe food allergies?
One family I know wipes everything down in public places, so that a stray peanutty-fingerprint does not wreak havoc. Based on that, it may have even been something on the outside of the food packaging?
Others have posted about similar concerns, I believe.
