Gluten Allergy Testing

Anyone suspecting an allergy to gluten or casein has several options as far as determining whether an allergy exists. All options have advantages and drawbacks, so it is important to do a little research beforehand.

The first test is known as a RAST test, which stands for radioallergosorbic test. Using a small sample of blood, it assesses the presence of IgE antibodies. IgE antibodies are produced in response to any allergen. So, if you are allergic to something, IgE antibodies will form and the RAST test can determine whether these are specific for gluten and casein. A positive test indicates an allergic response has occurred in the past. These tests are quite expensive, and it can take a while to get results back. It is also possible to have a negative RAST tests but still experience gluten or casein intolerances. Recently the CAP-RAST test has been developed and seems to be a more reliable test.

Challenge tests can also pinpoint gluten and casein allergies. These tests involve oral exposure to the suspected allergen in increasing doses until (or if) an allergic response is observed. The patient is given items to eat that either contain the allergen, or do not contain it, (which controls for the placebo effect) and the physician records when an allergic response is observed. These tests are not generally recommended if the allergic reaction is suspected to be severe, because of the risk of an anaphylactic reaction.

Skin prick tests are another option to test for gluten and casein allergies. Skin prick tests involve breaking the skin slightly and applying the suspected allergen to that area. If the patient is allergic to the substance, the area will become red, swollen and/or itchy. The size of the welt and the degree of itchiness corresponds to the severity of the allergy. These tests are relatively simple, pain free, inexpensive, and the results are clear within 15 to 20 minutes. Additionally, because the patient is exposed to so little of the allergen this test is deemed safe for even severe allergies. There are some downfalls to the skin prick test. These tests can be falsely negative especially if the patient is taking antihistamines.

Electrodermal screening is another option that is promoted by many naturopathic physicians. This test involves applying a slight electrical current to a point on the skin while the patient is wearing an electrode on the hand. When the current is applied, the amount of impedance between the stimulus and the electrode is measured. The physician can then make allergy diagnoses based on the degree of the impedance. This method is entirely safe, but extremely controversial because of the high number of false positives it renders.

An elimination diet is a test that any person can do on his or her own. This test involves eliminating suspected allergens from the diet completely, then adding them back gradually. When the offending allergen is added back into the diet, symptoms will return. There are a few drawbacks to this test. All traces of gluten and casein must be eliminated from the diet. To be accurate, an elimination test requires at least a month of eating a gluten-free and casein-free diet before foods can be reintroduced. No ‘cheating' is allowed. If any gluten or casein are eaten, the test must begin again. This is particularly difficult for gluten and casein, because they can both be hidden ingredients in many foods. Following these strict guidelines is difficult for some people. But, this test has the advantage of being very inexpensive and is a good option for people wanting to avoid a trip to the doctor's office.