What does the Food-Specific Immunoglobulin G test measure?

Why is Food-Specific Immunoglobulin G measured?

Food-specific IgG testing is widely used in functional and integrative medicine to guide elimination diets, but its clinical validity is contested. Mainstream allergy and gastroenterology societies — including the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology — state that IgG antibodies to foods reflect exposure, not pathology, and do not recommend IgG testing for the diagnosis of food allergy or intolerance. Proponents argue that patterns of IgG reactivity, particularly when correlated with symptoms and dietary trials, can identify foods contributing to chronic inflammation, gastrointestinal distress, and systemic complaints. Practitioners who order this panel typically do so to inform empirical elimination-rechallenge protocols rather than to establish a diagnosis.

Reference ranges

Standard reference

Results are reported as a semi-quantitative classification (negative, borderline, moderate, or high reactivity) for each of 144 foods, with assay-specific thresholds that are laboratory-defined rather than standardised across platforms.

Functional medicine optimal

There is no agreed optimal range for food-specific IgG. Elevated IgG to commonly consumed foods may simply reflect frequent exposure; interpretation should be symptom-driven and supported by supervised elimination–rechallenge rather than serology alone.

Units

Arbitrary units (AU), Qualitative class (0–3), Arbitrary Units (AU), Optical Density (OD), U/mL, Arbitrary Units, arbitrary units, Optical density (OD), Qualitative classification, Arbitrary units (U/mL or standardised scale), Qualitative (negative/borderline/positive), Units/mL, AU/mL, optical density, Optical density units, Qualitative scale, µg/mL

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.