I have had these blood tests done (IGG) for food sensitivities. I know I feel much better eliminating the foods the tests showed I had a high level of IGG antibodies to. I figured after finding a doctor who would order the tests, this is something I could do on my own, which I did. I didn't care who accepted it but its nice to know that perhaps mainstream medicine will come around.
The tests showed I had high IGG levels to wheat and other related grains (but not barley or oats and my biopsy for celiac was negative), casein, corn syrup, egg white and to a lesser degree, egg yolk. When I eliminated these foods from my diet I noticed a major improvement- very few mouth ulcers (and they were a major problem) and most joint pain I had at the time disappeared completely. I do have foot tendinitis now which seems resistant, unless I have developed another sensitivity (I didn't have the tests repeated, its been 2+ years) When I give in and eat something with casein (milk protein) I always get a some degree of mouth ulcer.
I sure wish they'd figure this out- makes sense to me that if the gut lining is not the way it should be, it is not performing properly. It is our first line of defense.