Here are a couple of articles on some research that my friend Gina sent to me that matches closely the allergy symptoms that I was having back in 2004:
1. The mystery of the tick and the allergy
2. Man's Sudden Food Allergy Was a Medical Mystery for Months
Basically, researchers have been looking at people with delayed-onset anaphylaxis after eating certain types of meat, and have managed to link their symptoms back to tick bites. And that does fit with my experience, as I was doing a lot more hiking back in the days when I had my allergies, and frequently had ticks. Something in the tick bite caused people to become allergic to galactose-alpha-1,3-galactose (a.k.a. alpha-gal).
Hence the testing for alpha-gal antibodies.
Update (6-20-12): Good Morning America has a story that pins this specifically on the Lone Star Tick.