A doctor may diagnose your allergies based on your symptoms, triggers, and test results. If your reactions are more severe and medications are not helping, an allergist may do a skin test to find out what your triggers are. You may need to book a number of appointments with the doctor for a final conclusion on what you are allergic too. You can expect to see an allergist more than once or twice, and in some cases three or four times, for your allergy to be determined.