Clinician reference tool — not medical advice. This is a clinical decision-aid intended for healthcare professionals: it gives deterministic suggestions to think with, not a diagnosis or a prescription. If you’re a patient, you’re welcome to look around — but please review anything here with your own doctor; it isn’t a substitute for personalized medical care.
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IgG / IgG4 food "sensitivity" testing

GI / immune · specimen: blood

No validated clinical use

Also called: food sensitivity test, food intolerance test, IgG food panel, IgG4 food panel, food-specific IgG antibody test, KBMO FIT test, Food Sensitivity Test, ALCAT test, Antigen Leukocyte Antibody test, leukocyte antigen antibody test, ELISA food allergy test, delayed food allergy test

Chart note

ND-recommended test reviewed: IgG / IgG4 food sensitivity panel (ALCAT/leukocyte antigen testing reviewed as related).
Indications reviewed: food sensitivity, intolerance, or elimination-diet guidance; features of IgE-mediated allergy not present.
Not ordered. Rationale discussed: food-specific IgG reflects exposure and tolerance, not disease; no validated use to identify symptom-causing foods. Ref: CSACI 2012; Choosing Wisely Canada.
Patient informed test available privately via ND. Patient given info page: https://labs.ajaxharwoodclinic.com/igg-food-sensitivity/patient
Revisit if: features of IgE-mediated allergy develop (hives, swelling, wheeze, anaphylaxis after a specific food).

Indicated when

None recorded.

Not indicated when

  • Ordering a panel of IgG or IgG4 antibodies to foods to diagnose food 'sensitivity' or intolerance, or to select foods for an elimination diet, in any patient [2, 1]
  • Using a leukocyte-reactivity test such as ALCAT (CONO 18, Antigen Leukocyte Antibody) for the same purpose: this is a different, unvalidated methodology offered for the same 'food sensitivity' indication, with no stronger evidence base located
  • Substituting any of these tests for allergen-specific IgE testing when the history suggests a true IgE-mediated allergy (hives, lip or throat swelling, wheeze, or anaphylaxis after a specific food) [3, 4]

Why not

Food-specific IgG is a marker of exposure and oral tolerance, not disease: the CSACI position statement notes that positive IgG results 'are to be expected in normal, healthy adults and children' who eat those foods regularly, so a positive result does not identify a food causing symptoms [1]. Acting on results drives unnecessary, sometimes broad dietary restriction, adds cost, and can cause confusion that leads to further unneeded referrals and investigations. There is also a specific safety concern: a patient with a true IgE-mediated allergy may not have an elevated IgG to that same allergen, and could be wrongly reassured and advised to reintroduce a food that carries a real anaphylaxis risk [1].

Better first step

If the history suggests a true food allergy (hives, angioedema, wheeze, vomiting, or anaphylaxis reproducibly after a specific food), refer for allergist-directed skin prick testing or serum allergen-specific IgE testing correlated to that history [4, 3]. If the concern is a non-IgE reaction such as bloating, diarrhea, or fatigue after eating, consider lactose intolerance, celiac disease, or a structured, supervised elimination-and-reintroduction diet, and assess for IBS.

Typical ND rationale

An ND may order an IgG or IgG4 food panel in a patient with bloating, fatigue, headaches, joint pain, or skin symptoms, reasoning that a delayed, non-IgE immune reaction to specific foods could be contributing, and that an elimination diet guided by the panel's results will identify and remove the trigger.

Where the ND is right

The underlying concern is legitimate: specific foods really can cause non-IgE-mediated symptoms, as in lactose intolerance, non-coeliac gluten/wheat sensitivity, or genuine dietary triggers of IBS, and these deserve real investigation rather than dismissal. No validated situation was identified, however, in which measuring IgG or IgG4 antibodies to foods, by any brand, panel, or methodology (including ALCAT), identifies which specific foods are responsible for a patient's symptoms.

Ontario coverage & CONO orderability

OHIP status
unverified
IgG or IgG4 food antibody testing, and Antigen Leukocyte Antibody (ALCAT) testing, do not appear by name anywhere in the 2026 Schedule of Benefits for Laboratory Services (searched in full for 'IgG', 'allergen', and 'antigen leukocyte'), so billing status if a physician were to order one is unverified. Choosing Wisely Canada's recommendation against ordering this testing [2] means a physician is unlikely to order it in practice. ND-ordered testing is privately paid regardless of insured status (Reg. 552 s.22(1); SOB-LS 2026 preamble).
CONO orderable
Yes — CONO list #7, #15, #18, #8
CONO 7 'Allergen Specific IgG Antibody' and CONO 15 'Antibody Screening Food IgG' are the direct food-IgG assays. CONO 18 'Antigen Leukocyte Antibody' (the branded ALCAT test) uses a different, cellular-reactivity methodology but is ordered for the same food-sensitivity indication and is included as an alias. CONO 8 'Allergy testing (ELISA)' is ambiguous on the CONO list (an ELISA format can run either an IgE-specific or an IgG-style panel); it is included as an alias with this note rather than assumed to be the validated IgE test, which is CONO 9 (not part of this record).

Linked conditions

Counselling script

“This IgG food test isn't something I'd order, because having IgG antibodies to a food is actually normal for people who eat it regularly, so a positive result doesn't tell us it's causing your symptoms. If certain foods really are triggering your symptoms, a structured elimination and reintroduction approach, or checking for a specific condition, gives us a much more reliable answer. And if you've ever had hives or swelling after a food, that's a different, important test we should do instead.”

Revisit if

  • Features of IgE-mediated allergy develop after a specific food (hives, angioedema, wheeze, vomiting, anaphylaxis)
  • Persistent GI symptoms despite reassurance, warranting assessment for celiac disease, lactose intolerance, or IBS

References

  1. [1]Canadian Society of Allergy and Clinical Immunology (2012). CSACI Position statement on the testing of food-specific IgG. linkolder guidelineCSACI position statement: no research supports using food-specific IgG to diagnose adverse food reactions; positive IgG is expected in healthy, tolerant people; risk of false reassurance in true IgE allergy
  2. [2]Canadian Society of Allergy and Clinical Immunology / Choosing Wisely Canada (2025). Allergy & Clinical Immunology: Eight Tests and Treatments to Question. linkChoosing Wisely Canada / CSACI: don't order specific IgG testing to panels of foods
  3. [3]Canadian Society of Clinical Chemists / Choosing Wisely Canada (2025). Clinical Biochemistry recommendations. linkChoosing Wisely Canada: don't order allergen-specific IgE tests unless indicated by history and correlated to specific exposures (contrast for the validated allergy test)
  4. [4]Canadian Society of Allergy and Clinical Immunology / Choosing Wisely Canada (2025). Allergy & Clinical Immunology: Eight Tests and Treatments to Question. linkChoosing Wisely Canada: don't order specific IgE tests unless indicated by history specific to that food
  5. [5]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkCommunity lab tests are insured only when ordered under the Schedule by an authorized prescriber
  6. [6]Government of Ontario (e-Laws) (2026). Health Insurance Act, R.R.O. 1990, Reg. 552: General, s. 22 (insured laboratory services). linkInsured lab testing requires ordering by an authorized provider who has clinically assessed the patient
  7. [7]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkTests ordered by anyone other than an authorized provider, including NDs, are not insured services
Evidence notes

ALCAT (CONO 18) was not separately researched as its own validated/unvalidated literature base in this session; it is grouped with IgG food-sensitivity testing based on identical marketed indication and the absence of any different, stronger evidence located. No Ontario source settles the billing status of this testing if a physician ordered it (none appears in the 2026 Schedule); marked unverified rather than assumed uninsured, per docs/research/ontario-coverage.md's rule that absence from the Schedule is not proof of non-coverage. 'Histamine intolerance' and 'MCAS' are listed as linked_conditions per the batch instructions because patients pursuing this test often frame their symptoms that way; the appropriateness of that link should be confirmed once those condition pages are drafted.