Symptoms of food allergies include vomiting, diarrhea, hives, swelling, respiratory distress, and rapid loss of blood pressure, among others, and happen within minutes and up to 2 hours after eating a food, though typically within 30 minutes. These symptoms are not just an inconvenience, they can quickly become life-threatening and require emergency medical attention. If you feel you have food allergies, please consult an allergist who is familiar with food allergies. Currently, testing for food allergy is done via skin prick test, IgE (only) blood test, and/or supervised food challenges - all done under the direction of a certified allergist, not your GP, naturopath, or other practitioner.
Allergy testing should only be done for foods which you suspect are causing the above allergy symptoms, as blindly testing random foods can produce false positives.
An elimination diet is the only way to prevent allergic reactions.