No matter what you call it its quite simple...
Gut dysbiosis.
Bad overgrowth of bad bacteria.
Basically leaky gut syndrome aka increased intestinal permiability causing immune reactions to undigested proteins in foods.
I already posted the link above for you for IGG food testing. A gp will not know much if anything about this condition and it is 100% proven medical fact.
You can also order a live stool analysis from pathlabs if you choose to see what bacteria has overgrown.
Depending on how bad it is determins what you do about it.
1.remove all offending foods
2.rotaiton diet
3.Kill the bad shit in their with natural remedies or if it is chroically bad pharmacuticals (not always needed)
4. fix gut mucosa
5. reseed bacteria with correct flora
6. be happy
7. proft?