Food sensitivity or intolerance is a contentious topic for healthcare professionals and patients alike. It is regularly the subject of intense media speculation and scrutiny. This scrutiny may be due in part to the clouded definition and misinformation of what actually constitutes a food sensitivity or intolerance. The typical immediate allergy response to shrimp or peanuts, for instance, is a well characterized phenomenon; classified as a Type I allergy. In certain individuals Type I allergies can be potentially fatal. For the purpose of this article, we will classify adverse reactions to food according the following definitions.
1. Food allergy: A response mediated by food-triggered basophil or mast cell histamine release. This reaction can be caused by either IgG or IgE food-specific antibodies. These reactions are immediate in nature and can be severe. This response is the Type I allergic reaction. Laboratory testing can help in the detection of food allergies or sensitivities.
2. Food sensitivity: A purely immune system-mediated response involving various classes of food-specific immunoglobulin molecules that can form food immune complexes. These complexes can stimulate the complement cascade and localized inflammation. These reactions tend to be delayed – from a few hours up to 7 days after food consumption – in some cases. This response is a Type III allergic reaction.
3. Food intolerance: A non-immunological mechanism of adverse food response. Examples would include lactose intolerance and MSG sensitivity.
Which IgG Test – 1, 4 or All?
The misinformation and lack of mechanistic explanations about IgG-mediated food sensitivity is reflected in the number of different IgG tests available to healthcare practitioners. Tests measuring total IgG subclasses (i.e.,1 through 4), IgG1, IgG4 or both IgG1&4 are available.
Information taken from Metametrix.com
"Understanding IgG4 Food Sensitivities." Metametrix. 2009. Metametrix, Web. 8/31/11.