IgG4 tests are invalid; IgG4 presence indicates that the person has been repeatedly exposed to food proteins recognized as foreign by the immune system which is a normal physiological response of the immune system after exposure to food components.[42][2] Although elimination of foods based on IgG-4 testing in IBS patients resulted in an improvement in symptoms,[43] the positive effects of food elimination were more likely due to wheat and milk elimination than IgG-4 test-determined factors.[44] The IgG-4 test specificity is questionable as healthy individuals with no symptoms of food intolerance also test positive for IgG-4 to several foods.[45]