Is IgG (Immunoglobulin G) and IgA (Immunoglobulin A) food sensitivity testing useful in patients with suspected food sensitivities or intolerances?

IgG and IgA Food Sensitivity Testing Has No Clinical Utility

IgG and IgA food sensitivity testing should not be used in clinical practice for diagnosing food allergies or sensitivities, as these tests lack validation, have no established diagnostic value, and can lead to harmful unnecessary dietary restrictions. 1

Why These Tests Are Not Recommended

IgG Testing Is Not Diagnostic of Food Allergy

• The NIAID expert panel explicitly states there is insufficient evidence to support food-specific IgG testing for diagnosing food allergy 1
• IgG antibodies to foods are a normal physiological response to food exposure and indicate tolerance, not allergy 2, 3
• Multiple studies demonstrate that IgG testing leads to false positive results and unnecessary elimination diets without clinical benefit 3, 4

IgA Testing Lacks Evidence Base

• No major allergy guidelines (NIAID 2010, EAACI 2014) recommend IgA testing for food sensitivity diagnosis 1
• IgA measurements have not been validated against the gold standard oral food challenge 2, 4
• There is no established correlation between food-specific IgA levels and clinical food reactions 2

What Tests Actually Work

For IgE-Mediated Food Allergy

• Skin prick testing (SPT) and serum food-specific IgE are the only validated tests for identifying IgE-mediated food allergies 1
• However, even these tests only indicate sensitization, not clinical allergy - they have poor positive predictive value (40-60%) 5
• 50-90% of presumed food allergies based on symptoms or positive tests are not true allergies when confirmed by oral food challenge 1, 5

The Gold Standard Remains Oral Food Challenge

• Double-blind placebo-controlled food challenge (DBPCFC) is the definitive diagnostic test 1, 2
• For atopic dermatitis patients, the American Academy of Dermatology recommends a diagnostic elimination diet (4-6 weeks) followed by oral food challenge if improvement occurs 5
• Positive skin tests or IgE results must be confirmed by oral challenge before implementing elimination diets 5

Critical Clinical Pitfalls

Harm from Unnecessary Elimination Diets

• Excessively restrictive diets based on unvalidated testing can cause weight loss, poor growth, calcium deficiency, hypovitaminosis, and kwashiorkor 5
• Unnecessary food avoidance significantly affects quality of life and nutrition 1
• Food allergies are clinically relevant in only a small subset of patients (usually those with moderate-to-severe disease) 5

The Diagnostic Algorithm That Works

1. Obtain detailed clinical history looking for consistent temporal correlation between specific food exposure and reproducible symptoms 1
2. If IgE-mediated allergy suspected: Perform SPT or food-specific IgE testing directed by history (not broad panels) 1
3. If tests positive: Implement short-term elimination diet (2-6 weeks) 1, 5
4. If improvement occurs: Confirm with supervised oral food challenge before long-term avoidance 5, 2
5. If non-IgE-mediated allergy suspected: Proceed directly to elimination diet followed by challenge 1

Bottom Line for Clinical Practice

Do not order IgG or IgA food sensitivity panels. These tests are marketed directly to consumers and practitioners with unsubstantiated claims 6, 3. They measure normal immune responses to food exposure, not pathologic reactions 2, 3. Using these tests leads to over-diagnosis, unnecessary dietary restrictions, and potential nutritional harm without improving patient outcomes 5, 3. When food allergy is suspected, use validated approaches: clinical history, SPT/specific IgE when appropriate, elimination diet, and oral food challenge 1, 5.