The 90 Food IgG ELISA Test is for measuring the relative amount of food-specific IgG antibody in human serum. . Specific allergens are immobilized separately onto microtiter wells. The allergens are allowed to react with specific antibodies present in the patient's serum. Excess serum proteins are removed by the wash step. Enzyme labeled antibody conjugate is allowed to react with allergen-antibody complex. A color is developed by the addition of a substrate that reacts with the coupled enzyme. The color intensity is measured and is directly proportional to the concentration of IgG antibody specific to a particular allergen.