Exercise induced allergies are an example of symptoms being provoked only when two (or more) factors are present at the same time. This makes it much harder to tease out the cause(s).
Food dependent exercise induced anaphylaxis (FDEIA) was first described in a case study in 1979, which seems fairly recent by medical standards. In comparison, Aspergers (now high functioning Autism) was first described in 1944.
Wheat allergy and delayed migraine connection was first confirmed through DBPCFC (double blind placebo controlled food challenge: the “gold standard”) in 2006.
Other possibilities such as free glutamates (MSG), NSAIDs amplifying allergic reaction have been described.
A study of WDEIA (wheat dependent exercise induced anaphylaxis)* shows that both aspirin and exercise increase the presence of gliadin in the blood stream** and the chronic induced behavior may extend to NSAIDs, MSG, Benzoate and other synthetic chemical food additives.
*Or GDEIA (gluten dependent exercise induced anaphylaxis)
**Morita E, Kunie K, Matsuo H (2007). “Food-dependent exercise-induced anaphylaxis”. J. Dermatol. Sci. 47 (2): 109–17. doi:10.1016/j.jdermsci.2007.03.004. PMID 17507204.