Thank you for your inquiry.
Based upon the history, with symptoms limited to the gastrointestinal tract, it is most likely that the reaction to bell peppers is food intolerance. However, there are clearly tests which would be helpful in distinguishing the difference between intolerance and allergy. These can be performed by skin tests as well as blood tests. If you wish to pursue this further, the American Academy of Allergy, Asthma, and Immunology website has a “Find an Allergist / Immunologist” section on the home page of the website. I would suggest that your patient seek the help of an allergist/immunologist to better answer this question. This can be done by simply evaluating a history.
To my knowledge, there is no relationship between intolerance to bell peppers and intolerance to aspartame. I could find no relationship between these two via a literature search, and the fact that fever was present suggests that the aspartame reaction is also intolerance rather than allergy.
Epinephrine would not be an effective means of treating a food intolerance reaction characterized by fever.
In summary, although the history is of course an extremely important tool to discern between reactions due to food intolerance and those due to food allergy, we have tests available to refine our diagnosis. Again, I would suggest that the patient you described seek care from an allergist/immunologist, especially in regards to the reaction to bell pepper, before coming to any specific conclusion in this regard.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.