It’s a marker of food tolerance, not sensitivity

Let’s examine the confusion over IgG4 in terms of how it relates to food allergy and sensitivity testing. The Precision Point Diagnostics P88 Dietary Antigen Test measures four different immunological reactions to 88 different foods, IgE (food allergies), IgG (food sensitivities), IgG4 (food tolerance), and C3d (complement- which in our case is a measure of the risk for a “complement cascade” associated with the IgG reaction, which means that a much more severe reaction is identified with that food that could be 1,000 to 10,000 the normal immunological response. Most food allergy and sensitivity testing (dietary antigen testing) are not nearly as multifaceted, rigorous, or as complex as that offered by Precision Point Diagnostics. There are some dietary antigen tests available, both here and in other countries (In Europe especially) that test only IgG4 as a method for detecting food sensitivities. This used to be more common but really hasn’t been the standard for 20 years or more. We’ve learned a lot more about the immunology of food allergies and food sensitivities in the intervening years. 

IgG4 measurements show a mediation of IgG reactions. In other words, when IgG4 measurements are positive, then it demonstrates a tolerance to allergic reactions to that same food. So, depending on how severe the IgE reaction, and how strong the IgG4 measurement, it may be that a patient has developed a safe tolerance to a food that they were once allergic to, or put another way, a patient’s allergic reaction has been overcome by IgG4 developed tolerance to that food and that food can be safely consumed. On the other hand, if the IgE reaction is stronger than the IgG4 reaction, but still not an extreme allergy, then it likely demonstrates that a tolerance to that food is building and a cautious diet that builds on that tolerance to increase it may be warranted. Highly allergenic foods will likely continue to be avoided without a special protocol for desensitization administered by the practitioner. The point is, it’s complicated, and based on fairly complex immunological science. The analysis of the interactions between these immunological responses is the heart of the Precision Point P88 DAT. What’s more, we’ve gone to great lengths to publish a detailed interpretive guide the the specific patient results that analyze these multifaceted interactions with every report. 

So why are we focusing on the confusion over IgG4 in contemporary criticism of dietary antigen tests? Sometimes conventional medicine is slow to catch up. For instance, the European Union recommends against using IgG4 as a testing method to determine food intolerance: Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report states “Serological tests for immunoglobulin G4 (IgG4) against foods are persistently promoted for the diagnosis of food-induced hypersensitivity.” and “In contrast to the disputed beliefs, IgG4 against foods indicates that the organism has been repeatedly exposed to food components, recognized as foreign proteins by the immune system. Its presence should not be considered as a factor which induces hypersensitivity, but rather as an indicator for immunological tolerance, linked to the activity of regulatory T cells.” Clearly, the EU is concerned with labs that use IgG4 as a marker of sensitivity, and point out that it instead indicates tolerance- which is exactly how the P88 assesses IgG4. 

One concern that is sometimes expressed in addition to the fact that IgG4 is a marker of mediation rather than of sensitivity is that testing for IgG or IgG4 might mask true allergies and give a false sense of security to a patient when IgG doesn’t show a reaction for a food that there is either a known or unknown allergy to. This is only a concern when IgE testing is not simultaneously or subsequently conducted. Again, the Precision Point Diagnostics P88 includes IgE reactions (allergic responses) on the panel, and not only gauges the severity of those reactions but also compares them to their IgG4 mediations for each food tested. Remember when looking at the report for the P88:

1. IgE measures the intensity of an allergic reaction to that particular food
2. IgG4 measures the degree of mediation (tolerance) to an IgE reaction from a particular food. The P88 report shows both IgE and IgG4 reactions side by side for ease of interpretation.
3. IgG measures food sensitivities, not true food allergies. Food sensitivities tend to have a longer time of onset for symptoms to appear, from 3-72 hours usually. Food sensitivity symptoms can vary from those caused by food allergies and can include headaches, fatigue, brain fog, general inflammation, and digestive upset.
4. Complement (C3d) measures the capacity for a complement cascade to be triggered by an IgG reaction from a particular food. Such a cascade can cause a surge in inflammatory action that can be 1,000 times greater than that which may occur without the cascade.