In the UK, blood tests for immunoglobulin G4 (IgG4) against foods are actively promoted for the diagnosis of food intolerance and hypersensitivity. Mounting clinical research indicates that food-specific IgG4 allergy testing does not indicate (imminent) food allergy or intolerance, but is rather a normal physiological response by the immune system after food exposure. In fact IgG4 is more likely to indicate food tolerance and that the person can safely eat that food with no adverse effect. This should not be confused with IgE which is the main allergy antibody used in allergy testing and this has an established “track record” in conventional allergy diagnosis.
Not really convinced? Have a look at these research papers:
No recommendation for IgG and IgG4 testing against foods
J. Kleine-Tebbe, I. Reese, B. K. Ballmer-Weber, K. Beyer, S. Erdmann, Th. Fuchs, M. Henzgen, A. Heratizadeh, I. Hutt egger, L. Jäger, U. Jappe, U. Lepp, B. Niggemann, et al Allergo J 2009;4: 267
Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report*
Stapel SO, Asero R, Ballmer-Weber BK, Knol EF, Strobel S, Vieths S, Kleine-Tebbe J.
Allergy 2008 July;63(7):793-796.
Unproven techniques in allergy diagnosis.
J Investig Allergol Clin Immunol 2005;15(2):2-90