The problem with food allergies and sensitivities
Once the body gets a food into the system that creates a reaction, that reaction ultimately leads to inflammation. The next phase after inflammation is damage. In the case of joint pain (arthritis), inflammation is going to cause damage to the collagen lining the bones of the joint. Long term inflammation of that joint will harm the body's ability to regenerate and eventually will lead to osteoarthritis or chronic degenerative disease.
We see chronic food allergies causing damage to the thyroid, which can result in the thyroid going into overfunctioning or underfunctioning. Because food goes through the alimentary canal (gastrointestinal tract), food allergies/sensitivities can cause stomach dysfunction (reflux, heartburn or gastritis) or conditions like Irritable Bowel Syndrome.
The idea is that single immunological reactions can cause some short term symptoms which the body is capable of recovering from. However, foods that are problematic for us that we eat over and over for years can result in some of the organs, glands, or tissues of the body functioning in an abnormal way.
Food allergies are an immunological reaction to a food or a food ingredient. In other words, allergies involve the immune system of the body forming antibodies (typically IgE or IgG) to an antigen (foreign substance). Allergies can be histamine-based (producing some combination of hives, redness, swelling, mucous, or even anaphylaxis) or not involve histamine at all. Typical Celiac's Disease, where people react to the gliadin component of gluten (a protein which is in wheat in addition to other grains), is an example of a food allergy (typically IgG) where there is no histamine reaction.
Food sensitivities are simply "food or a food ingredient that your body doesn't like." Because of it's broad definition, food allergies would fall into this category. This menas that a food allergy is a food sensitivity, but one could have a food sensitivity that is not also a food allergy. A diabetic could have problems with certain types of sugars, but you wouldn't call those food allergies. Other examples of conditions where it's more likely a food sensitivity would include lactose intolerance, MSG (monosodium glutamate) sensitivity, or a situation where a patient reacts to refined or processed food but they're fine on whole grain or unpasteurized dairy products.
Modes of testing
There are plenty of ways to test for food sensitivities. Medical doctors have a tendency to use scratch tests or RAST tests. Both are excellent tests if the allergy is histaminic. If the reaction is not an allergy or is an allergy but it is IgG based, then the test is going to say there is no problem with that food when in reality there is. Alternative practitioners tend to use more companies that look at a broader spectrum of reactions. A very short list of labs that run these kinds of tests include: SAGE testing which tests for immune complexes (www.sagemedlab.com), and Cyrex Labs (www.cyrexlabs.com) and Genova (www.gdx.net) and ImmunoLabs (www.immunolabs.coms) which measure antibodies, and then finally ELISA ACT (www.elisaact.com) and ALCAT (www.alcat.com) which measure the patient's own (lymphocyte) cell reactions to different potential allergens. Although he has access to these labs and is willing to utilize them at a patient's request, Dr. Berglund prefers to use a much more cost-effective type of testing that he offers in-house.