Can a primary care doctor order blood tests for food allergies? is it fair to ask them to?

Yes...but: Primary care doctors can order blood testing for food allergies but they will often refer you to an allergist for interpretation if positive. They also might diagnose you with a food allergy that you might not have because they are not as experienced interpreting results. I would recommend seeing an allergist first if concerned about food allergies, better to go straight to the experts.