I feel sure good liver health is a key to getting rid of allergies. In 2000 I did the 8 weeks dietary liver cleanse described in the book The Liver Cleansing Diet. Before it was over I was able to stop taking allergy shots, and my allergies and sensitivities have steadily improved as I continue to follow many parts of the diet as a way of life.
As to food reactions , you might look into intestinal dysbiosis. Jordan Rubin's Primal Defense probiotic product helped me a great deal with that.