IgG Food Allergy Testing Is Not Valid
IgG food allergy testing is not a valid diagnostic approach and should not be used for evaluating food allergies in children. 1, 2
Why IgG Testing Is Not Recommended
IgG4 food testing is explicitly not recommended for assessment of food allergy. 1 The presence of food-specific IgG antibodies represents a normal physiological response to food exposure, not an allergic reaction, and continues to be an unproven or experimental test that lacks scientific validity. 2
Valid Diagnostic Tests for Food Allergy
The three evidence-based diagnostic tests for food allergy are:
- Skin prick testing - directly assesses mast cell-bound allergen-specific IgE with a negative predictive value exceeding 95% 1
- Specific serum IgE testing - quantifies free specific serum IgE antibodies 1
- Oral food challenge - remains the gold standard for definitive diagnosis 1, 3, 4, 5
Critical Diagnostic Principles
Testing should only be performed when there is clinical suspicion based on a symptom-provoking episode. 1 Testing without suspicion of symptoms is not recommended and findings are often misleading due to false-positive results. 1
A positive allergy test result alone does not establish the diagnosis of clinical food allergy. 1, 6 Rather, it provides evidence of sensitization (an immunologic response), which must be correlated with the patient's clinical history. 1
The Diagnostic Algorithm
Document clinical history - symptoms must have occurred reproducibly after exposure to a specific food, typically within minutes to hours after ingestion 1, 3
Perform appropriate testing - use skin prick testing and/or specific serum IgE testing only for foods suspected based on clinical history 1
Correlate results with history - all positive and negative test results need clinical correlation 1, 6
Consider oral food challenge - when testing results are unclear or to verify tolerance, perform controlled oral food challenges under specialist supervision 1, 7, 3, 4, 5
Common Pitfalls to Avoid
Do not use laboratory-offered standard panels of common foods. 1 Testing should be limited to what reasonably may have provoked the reaction based on clinical history. 1
Avoid relying solely on positive IgE testing without clinical history, as sensitization does not equal clinical allergy. 8, 6 IgE testing has poor positive predictive value despite being sensitive in detecting allergen-specific IgE. 7, 6
Do not implement unnecessary dietary restrictions in children without documented food allergy. 8, 6 Research demonstrates that nearly 89% of avoidance diets in children with atopic dermatitis and food allergy diagnosed by serum-specific IgE were unnecessary, and nutritional deficits have been reported from widespread dietary avoidance. 1
Immediate Management Steps
If a child has clinical symptoms suggesting food allergy:
- Prescribe epinephrine autoinjector and antihistamines immediately 1, 7, 8
- Refer to an allergist for definitive diagnostic testing 1, 7, 8
- Instruct temporary avoidance of the suspected food until allergist evaluation 7
- Provide emergency action plan training on recognizing anaphylaxis symptoms and proper epinephrine administration 1, 7, 8
Children wait an average of 4 months for allergist consultation and remain at risk for life-threatening reactions during this period, making immediate prescription of emergency medications essential even when diagnostic certainty is lacking. 1, 8