Reason for the food allergies is impaired intestinal barrier (leaky gut). You heal it by avoiding gluten and alcohol , vegetable oils, coffee permanently and the foods that you react to temporarily. Also vitamin D level (from suntanning preferably), increase saturated fat intake, google Paleo diet or even better Autoimmune paleo diet. If done right takes 4-8 months.
This way I healed my intestines to the extent that i can eat fructose and dairy daily, and I no longer have the reaction I used to have.