Delayed allergic reaction- anaphylaxis

My husband started having what we thought were random anaphylactic episodes in the middle of the night. He’d wake up with gastric issues- burping, etc, then he’d get hot, clammy and ultimately start to experience swelling in his mouth and difficulty breathing. Each time this happened we took him to the ER, steroids and a few epi pens and 4-5 hours later and he’d be released. As the years passed this allergic reaction became more common and we narrowed it down to it was on the evenings that he ate meat. After a ton of research we learned about Alpha Gal and was certain that was it. We started avoiding meat and he then started reacting to dairy as well, which again can be part of Alpha Gal. No drs in our area knew anything about Alpha Gal so we found a specialist in another state at a famous hospital. We drove there yesterday, they suggested we do a controlled test, we are now into hour 5, no reaction. The dr said Alpha Gal never goes over 6 hours…. We’re at a total loss now. His reactions only ever happen in the middle of the night 2:00-3:30 AM and this is a morning- afternoon test.
We’re about to be released and still no answers… has anyone experienced this? Any drs ever hear of anything like this?
He’s scared to eat, it’s truly affecting our lives at this point.

Thank you in advance.