The first order of business when you suspect you are sensitive to, allergic to or intolerant of a substance is to begin keeping a diary of your reactions and what you have been doing, eating and drinking for the 72 hours prior to the response. Of course, if the response is severe you will probably be experiencing an immediate reaction and should seek immediate medical attention. On the other hand, if your suspected sensitivity or allergy is to a substance you can easily avoid and your symptoms are minor, it may not be necessary to formally test and diagnose the allergy at all. The degree to which you are inconvenienced or made ill by the allergy will probably be your best guide as to whether you will seek a diagnosis or merely employ some of the desensitization and avoidance techniques we will discuss in later sections.
There are surprisingly few methods of testing for allergies, and some are more effective for diagnosing certain types of allergens than others. We will explore each in detail.
There are three main types of skin testing, all of which primarily identify IgE-medicated allergic responses. They are the skin prick or scratch test, the intradermal test, and the skin patch test.
Skin Prick/Scratch Test
This is the conventional method for identifying allergens responsible for IgE-mediated allergic responses such as allergic rhinitis, eczema, hives and asthma. Typically, responses such as these are triggered by inhaled allergens such as pollen, mold, dust mites or animal dander. Unfortunately, this type of test is only about 15% effective in detecting food allergies according to one researcher.
The skin test procedure is very simple: the doctor lightly scratches or uses a fine needle to lightly prick the skin in a pre-determined pattern. Small dilutions of the suspected allergens are then introduced carefully to each damaged skin area so that the allergen can enter the body. If a wheal (a reddish inflammation similar to a mosquito bite) develops within 20 minutes, an allergy to the substance is confirmed. It may require several sessions to test for every allergen, with the most common ones being tested first. Here is where your diary may come in handy, to suggest a more efficient order of testing than if you were to simply go to your allergist and ask to be tested for all known allergens.
This test is performed when the skin prick test does not show a reaction to the allergen, but it is still suspected as the cause of an individual?s reaction. The intradermal test is more sensitive than the skin prick test, but is also responsible for more false positive results. In this test, the allergen solution is injected into the skin.
Skin Patch Test
This test is used to detect contact dermatitis, a type of allergy or sensitivity that causes a rash upon contact. To perform it, the suspected allergen is placed on a pad that is then taped to the person?s skin for 24 to 72 hours.
Laboratory Blood Testing
Blood tests may not be as sensitive as skin tests, but for allergies that are not easily determined by skin testing, or for individuals that for some reason cannot have a skin test, several blood tests are available.
IgG ELISA Test
Testing for food allergies can be more challenging than determining environmental allergy responses. Most food allergies are dealt with by IgG antibodies, whereas the traditional skin prick test measures only the IgE-mediated responses. For this reason, many practitioners, particularly those well versed in alternative medicine; consider the ELISA test to be one of the most sensitive and therefore most useful blood tests to detect delayed food allergies. ELISA stands for enzyme-linked immunoserological assay.
To perform this test, a small blood sample is taken from the patient and then delivered within 72 hours to a specialized laboratory that is equipped to process the assay. Here, technicians collect the IgG antibodies within the sample, and place a drop of the serum containing the antibodies into a laboratory testing plate consisting of many tiny depressions or ?wells?. Each of these wells contains a single food or component of food, such as gluten, that are known to be potentially allergenic. A computer then analyzes the samples for reaction to the food. A positive reaction indicates that the specific IgG antibody to that food exists within the sample, and means that an allergic response will occur within the individual?s body when that food is ingested, particularly in the presence of leaky gut syndrome.