Allergies & Sensitivities Testing Methods

The most reliable way to determine a food allergy is to have the patient eliminate a suspected food from the diet for a period of time and then reintroduce it later. Once a food is eliminated, the symptoms it may be causing either improve or resolve, typically between several days and three weeks. The body's sensitivity to the food then increases, so when the food is reintroduced the symptom is more likely to recur. With a high degree of certainty this tool shows which foods are problematic. The testing requires a great deal of patience and, as with all other forms of allergy testing, it is best undertaken with the help of a physician who can monitor the diet. Occasionally, reintroduction of an allergenic food has been reported to induce dangerous reactions in people with certain conditions, particularly asthma. This is yet another reason this approach should not be attempted without supervision.

This form of testing is one of the most widely used. A patient's skin is scratched with a needle that contains a portion of the food, inhalant, or chemical that is being tested. After a period of time, the skin is examined for reactions. If there is a reaction, it is determined that an allergy exists. Although this test is accepted by most allergists, scratch testing is marked by a relatively high incidence of inaccurate results, some tests showing positive when the person is not truly allergic to the substance (false positive) and some tests showing negative when an allergy really exists (false negative).

(and other tests that measure immunoglobulins)
The radioallergosorbent test (RAST) indirectly measures antibodies in the blood that react to specific foods. It is used by many physicians and has been shown to be a somewhat reliable indicator of allergies (164, 165). It does not, however, help diagnose non-allergic food sensitivities and is therefore associated with a high risk of false negative readings. In an attempt to avoid this problem, a variety of modifications have been made to tests related to RAST (such as MAST, PRIST, and ELISA). Some of these changes may have reduced the risk of false negative readings somewhat, but, as a result, these modified tests are likely to have increased the risk of false positive readings. A number of conditions associated with food sensitivities, such as migraine headaches and irritable bowel syndrome, have shown remarkably poor correlation between RAST results and the actual sensitivities of patients.

The cytotoxic test views a patient's serum under a microscope to see whether it is reacting to certain substances. The test is subject to numerous errors and is not generally considered to be reliable.

(provocation-neutralization; end-point titration)
This branch of medicine is considered to be very controversial. Testing is done using intra-dermal (under the skin) injections of minute dilutions of foods, inhalants, or, in some cases, chemicals. Based on reactions, additional dilutions are used. This test not only determines whether an allergy exists but also operates on the theory that one dilution can trigger a reaction while another can neutralize a reaction. Preliminary research suggests this approach may have beneficial effects. A similar method uses these dilutions under the tongue to test for allergies. Double-blind research has not found this method effective.

Bioelectric tests are controversial procedures that attempt to measure changes in electrical activity at acupuncture points when a potential allergen is brought into proximity. A preliminary study reported that the EAV (Electroacupuncture According to Voll) device, also called the Vega test, identified the same allergens as RAST testing in 70.5 percent of tests. Another preliminary study found the Vega test identified the same neutralization doses as clinical ecology testing (see above) in 66% of tests. More research is needed to better evaluate these testing techniques.