My mantra is “test – don’t guess” – this is what I do in my Clinic. Yes, in my Clinic I see a great number of babies, children and adults with a variety of different illnesses. But they have only a narrow range of symptoms. Many of these people are ill because of food allergy or food intolerance. To work out what is wrong with them, they need testing. Yes, “test – don’t guess”. I often get asked “Is IgG food allergy test better/more accurate than a RAST.” Well, IgG and IgE testing are quite different, and give different information.
To simply matters, IgE testing is used for IMMEDIATE-onset reactions (within 5-20 minutes), and IgG eating for DELAYED-onset reactions (after hours or days).
To really understand and interpret the tests, you need to know about the big range of food-related illnesses, the mechanisms and the diagnostic tests.
Here is the list of the more common food-related disorders. The confusing thing is that you can get similar symptoms from a range of different food-reactive immune responses. Also, people can have more than one type of reaction happening simultaneously to different food.
Delayed Food Intolerance is often driven by IgG antibodies to specific foods
Immediate Food Allergy is usually driven by IgE antibodies to specific foods
Gluten-related disorders: gluten-intolerance and celiac disease.
Oral food allergy syndrome: driven by IgE antibodies to specific pollens
Histamine intolerance: symptoms caused by histamine-releasing foods.
Food additive reactions: symptoms caused by E color chemicals 102, 104, 110, 122, 124, 129
Natural chemical reactions: symptoms caused by salicylates, amines, MSG
Enzyme deficiencies: Lactose intolerance, Congenital Sucrase-Isomaltase deficiency (CSID)
Is IgG food allergy test better/more accurate than a RAST?
Importantly, IgG and IgE testing are quite different.
Specific IgE can be tested by two methods:
1) Skin prick testing
2) EAST/RAST blood tests measure specific-IgE (this is for making the diagnosis of IMMEDIATE food allergy (within a few minutes of having the food). It gives the same information as a skin-prick-test for allergy).
IgG food sensitivity testing
Testing for IgG specific antibody looks at the possibility of DELAYED-onset food allergy (few hours or next day). Skin-prick-tests and RAST tests will usually be negative.
Both tests are useful to work out the problem. We can offering IgG-food-allergen testing through the US BioTek laboratory.