I am confused surely a non-IgE allergy is not an allergy but just an intolerance. Does a non-IgE allergy ever lead to anaphylactic shock?
My children all had severe intolerance when they were young, causing bleeding from the acid pooped out, screaming in pain (too young for them to know what was going on, being managed by a dietitian to work out their intolerance.) It meant that going out for a family meal was a nightmare, but I would never say they had an allergy as it blatantly was not true. They had severe intolerance and I would never give them a "treat" of what they were intolerant to as it would be no treat later for them.
Each of the children reacted at different timescales and severity to MSG, so we have always been very careful with avoiding foods with added MSG. The oldest child reacts within 15 minutes with stomach pain and depending on the amount consumed either vomiting or acidic diarrhea or both...., the next child does not react til the next day, and gets stomach pain and diarrhea, the youngest child does not react til two days after eating it and just gets a mild stomach discomfort and diarrhea. All three will vomit within hours if they consume a significant amount of MSG.
So one family meal out where we have been inadvertently given added MSG and we have three days of fun, it did help us eliminate restaurants from possible places to go! It got to the point where we knew that the only "safe" place we could eat out as a family was McDonald's, as their allergy lists were most accurate, not the most healthy option.
When I was in primary school I remember the school dinner ladies getting fed up with children being fussy and not eating the rice pudding option when other options ran out. I told them I could not eat the milk (never drank the milk bottles!), they did not believe me and stood over me while making me eat it. The result was inevitable, I threw up all over the table. !!! The only time my whole life I have ever been able to drink milk is while pregnant, otherwise it rebounds nicely. I wish I could "treat" myself to a cool glass of milk sometimes, but would never inflict it on myself.