Allergy, intolerance,?

Patient: When I eat, I turn red from my face down to my chest. It starts instantaneously after my first bite. It starts out being blotchy, then completely turns red. My throat gets thick and I produce mucus and cough frequently and it seems I can’t clear my throat. When I swallow it feels like a large bolus going down,slightly uncomfortable and sometimes painful. The only time that this doesn’t happen is when I eat something really bland, like bread or drink something like milk. My face burns with heat and people frequently ask if I have been crying.It has been doing this for a couple of years, but the severity has developed over time. I have had food allergy testing and they all came back negative. My question is, what could be causing this?