How Bad of an Allergy Attack Requires an Epipen?

I have food allergies and am prescribed an Epi-Pen. I am allergic to peanut, cashew, pistachio, and a few other nuts. Occionally I do get exposed to the allergen. I do not go into a SEVERE reaction, per say, but my throat does swell up a little bit and my stomach gets extremely upset. After I vomit, I feel excruciating pain move through my digestive tract as the remaining allergen pes, irritating each inch of intestine as it moves along. Finally I'll have a few bouts of diarrhea and then be generally back to normal after about 3-4 hours. The swelling of my throat usually goes down after I vomit and only minorly obstructs my breathing. What I've wondered, is how much of this would an Epi-Pen injection affect?