Allergy Tests and their Limitations  

By Barbara Bourke (Adv.Dip of Nutrition)

The first step your doctor will probably take when allergies are suspected is send you off for a skin or blood test. Medical allergy tests include the skin prick test, patch test or blood tests like the RAST blood test. 

Let's have a closer look at these tests.

A skin prick testinvolves putting drops of a variety of suspected allergens (for example pollen, dust mites, pet hair, mould, foods) using a pin-prick, usually on the forearm. Sensitivity to a particular allergen will show itself with an itchy, red, raised wheal. Skin prick tests are a way of checking sensitivity to inhaled allergens such as pollen or dust mite, but are not so effective at detecting sensitivity to foods. This test is uncomfortable and only a limited number of allergens can be tested at one time.

Patch testing is a way of identifying whether a substance that comes in contact with the skin is causing inflammation of the skin. With the patch test you need to leave the patch (usually placed on your arm) on for about 24 hours. This patch contains a suspected allergen and again a local reaction of the skin needs to occur for a positive result.

Blood tests will look for elevated antibodies also known as Immunoglobulin (Ig's), which is a type of protein. Those immunoglobulins are the weapons of the immune system to identify and destroy invading antigen and other foreign objects. There are 5 different types of Ig's and each one has a specific job to do. Blood allergy tests look for particular Ig's.

In autoimmune conditions this protective system is malfunctioning as it is mistaking its own tissue as the enemy.

Blood tests for allergen specific IgE antibodies RAST (radioallergosorbent) test determine sensitivity to suspected allergens. Whereas the skin prick test result is available immediately, RAST results are often not available for a few days and may be more expensive than skin testing. However, RAST testing is a useful alternative when skin prick testing is not possible, as in a bad case of a skin condition or if a reaction is not advisable. The Wikipedia Encyclopedia states that a more superior test has been developed in 1989 called CAP FEIA (fluorenzymeimmunoassay).

Blood test for IgG is a blood test for non-immunological adverse reaction to the sensitivities to common foods.

IgA is found in the saliva, gastric fluids, plasma and mucous membrane of the body. It is believed that IgA is the link between gut-related health conditions and the systemic illness and is usually associated with altered intestinal permeability (leaky gut). It is responsible for immune protection within the gut. Stress, Candida, Coeliac disease, Crohn’s disease and other auto immune conditions and also food sensitivities can be responsible for elevated levels.

The above are the most common medical allergy tests available.

Ok, you have been for your blood or skin test, which tested you, for lets say between 10 to 100 different items. Those may be foods, dust, pollen, grasses, fibers, chemicals etc etc. You have your list and you think all is well as long as you stay away from those dreaded allergy causing items. Your doctor agrees and might send you home with some antihistamine medication or what ever else could be of help.

This is most probably not the end of your allergy reactions. Why?

What about the other thousands upon thousands of food items, chemicals, natural and synthetics fibers, toothpastes, washing powders, soaps… the list is long. What about items you have not been tested for? Anyone of those could potentially induce an allergic reaction. Even healthy and organic foods are not excluded. If you have not been given a list of safe foods or other items for you personally then I believe the test is not worth the paper it is written on. This might sound harsh, but usually it is not an isolated item, causing the allergy.

Allergies are accumulative and the inflammation they cause encourage secondary allergies. All of those items need to be removed from your diet and life for a certain amount of time. This will start the healing process. But how can you know what else is causing you allergy reactions if you only been tested for 100 or so items.

Many Allergy tests are not specific enough and that's where their limitations lay. Most tests provide you only with a broad idea of what you are allergic too and are not able to advise you on safe alternatives. Any allergy test, whether, blood, skin or any other kind, will offer very limited success, unless it can provide you with a list of safe foods and products, specific for you.