If you think you have a food allergy, don't go and see your doctor. He or she may not be able to identify the allergy in the first place, and almost certainly won't have a good way of testing for it. Researchers from Stanford University discovered medicine's ignorance and uncertainty about food allergies when they sifted through thousands of research papers. There isn't even an agreed definition of what a food allergy actually is, or how it differs from a food intolerance, and nobody seems to agree on a reliable test. The standard test - where a doctor gives a sample of the suspected allergy, and checks for allergic reaction - usually requires specialised staff, and is expensive. Other tests include pricking the skin or taking blood, but they rarely produce absolute proof of an allergy. Too often, the doctor diagnoses a food allergy when, in fact, the patient has an intolerance. It's a life-changing diagnosis, and it's often wrong, say the Stanford researchers. (Source: Journal of the American Medical Association, 2010; 303: 1848-56).