Why Allergy Tests Don't Work for Food Sensitivities

When food is making you miserable and you can't figure out which one, a blood test that promises answers sounds like a lifeline. Labs market IgG panels, ALCAT tests, and MRT (Mediator Release Test) as the way to finally identify your trigger foods. There's just one problem: major medical organizations worldwide say these tests are not validated for diagnosing food sensitivities.

Allergy vs. Sensitivity vs. Intolerance: Why It Matters

Before we get into why the tests fail, you need to understand what you're actually dealing with. These three terms describe fundamentally different mechanisms in your body:

Food Allergy (IgE-Mediated)

True food allergies involve your immune system's IgE antibodies. They cause rapid, often severe reactions: hives, throat swelling, anaphylaxis. These are the reactions that send people to the ER. Standard allergy tests (skin prick, IgE blood tests) are designed for these reactions and they work well.

Food Sensitivity (Non-IgE Immune Reactions)

Sensitivities may involve other parts of the immune system (IgG, IgA, complement, T-cells) or inflammatory pathways that don't follow the classic allergy model. Symptoms are typically delayed by hours to up to 72 hours, making the trigger food extremely hard to identify. This is where people get stuck in a cycle of bloating, brain fog, joint pain, skin flares, and fatigue without knowing why.

Food Intolerance (Non-Immune)

Intolerances are enzyme-based or chemical reactions. Lactose intolerance is the classic example: you lack the lactase enzyme to break down milk sugar. Histamine intolerance is another common one. These don't involve your immune system at all, which is precisely why immune-based tests can't detect them.

The Tests That Don't Work (and Why)

IgG Food Panels

IgG food sensitivity panels are the most widely marketed test, often costing $200-$600. They measure IgG antibodies to dozens or hundreds of foods. The concept sounds logical: if your body makes antibodies against a food, that food must be a problem.

The science says otherwise. IgG antibodies to food are a normal part of immune function. They indicate exposure, not intolerance. Your body produces IgG antibodies to foods you eat regularly, including foods you tolerate perfectly well. In fact, research suggests that IgG4 antibodies to food may actually indicate tolerance, not sensitivity.

This is why every major allergy organization in the world has issued position statements against using IgG testing for food sensitivity diagnosis:

• The European Academy of Allergy and Clinical Immunology (EAACI) states IgG4 testing is irrelevant for food allergy or intolerance diagnosis
• The American Academy of Allergy, Asthma & Immunology (AAAAI) recommends against IgG testing for food sensitivity
• The Canadian Society of Allergy and Clinical Immunology (CSACI) has formally discouraged IgG food testing
• The Australasian Society of Clinical Immunology and Allergy (ASCIA) classifies IgG food testing as unproven

ALCAT Test (Antigen Leukocyte Cellular Antibody Test)

The ALCAT test measures changes in white blood cell size and number after exposure to food extracts. It's been marketed since the 1980s as a way to detect food sensitivities.

Independent peer-reviewed studies have found the ALCAT test has poor reproducibility. When the same blood sample is tested twice, results frequently differ. A test that can't give the same answer twice for the same sample is not clinically reliable.

MRT (Mediator Release Test)

The MRT test measures changes in the ratio of solids to liquids in blood after exposure to food antigens, which is interpreted as mediator release from white blood cells. It is marketed as more advanced than ALCAT.

While the MRT test uses patented LEAP (Lifestyle Eating and Performance) technology, it lacks sufficient independent peer-reviewed validation. Most published evidence supporting MRT comes from studies with limited scope or potential conflicts of interest. It has not been independently validated by the level of rigorous clinical trials required for widespread medical adoption.

The 2025 IBS Study: A Partial Exception?

A 2025 study published in The Lancet Gastroenterology & Hepatology found that an IgG4-guided elimination diet improved symptoms in IBS patients compared to a sham diet. This has generated significant discussion in the medical community.

However, this result is specific to IBS and does not validate IgG testing for general food sensitivities. The study authors themselves noted that IgG4 may be acting as a marker of dietary exposure rather than a direct cause of symptoms. Further replication studies are needed before clinical guidelines change.

What Actually Works

Validated Testing Methods

For specific, well-defined conditions, validated diagnostic tests do exist:

• Skin prick tests and serum IgE for true IgE-mediated food allergies
• Hydrogen breath tests for lactose malabsorption (reliable and well-validated). Breath tests for fructose malabsorption exist but have lower reliability according to recent research
• Celiac serology (tTG-IgA) plus duodenal biopsy for celiac disease
• Serum tryptase and clinical history for mast cell disorders
• Oral food challenges conducted under medical supervision (the definitive test for food allergy)

The Gold Standard: Elimination Diet + Systematic Tracking

For the broad category of food sensitivities and intolerances, the elimination diet remains the gold standard recommended by gastroenterologists and allergists worldwide. Here's why it works when blood tests don't:

• It captures all mechanisms - immune, enzymatic, chemical, and combination reactions
• It accounts for delayed reactions - symptoms can appear up to 72 hours after eating a trigger food
• It reveals dose-dependent triggers - some foods only cause problems above a certain quantity
• It identifies combination triggers - some reactions only happen when certain foods are eaten together
• It shows YOUR unique pattern - not a generic antibody level that may mean nothing

This is exactly why carnivore and animal-based elimination approaches have gained traction. By starting from a clean baseline of well-tolerated animal foods, you can systematically reintroduce foods one at a time and track exactly what happens in YOUR body.

This Applies to Your Pets Too

If you've been through the frustration of food sensitivity testing for yourself, you may recognize the same pattern playing out at the vet. Dogs and cats suffer from food sensitivities too, and the veterinary world faces the same testing limitations.

• Saliva and hair tests for pets have no scientific backing whatsoever
• Serum IgE testing in dogs is validated for environmental allergies (atopy) but is unreliable for food sensitivities
• Veterinary elimination diets (novel protein or hydrolyzed protein trials lasting 8-12 weeks) remain the gold standard for diagnosing food-related adverse reactions in animals

The same principle applies: systematic elimination and careful tracking of what your pet eats and how they respond is the only reliable way to identify their trigger foods.

Why Tracking Beats Testing

A blood test gives you a single snapshot. Tracking gives you a living dataset that reveals your body's real-world responses over time. Here's what consistent tracking can uncover that no lab test can:

• Delayed reactions that appear up to 72 hours after eating a trigger
• Cumulative effects where small amounts are fine but repeated exposure causes symptoms
• Contextual triggers like stress, sleep, or hormonal cycles that amplify food reactions
• Changing sensitivities that shift as your gut heals or as seasons change
• Combination effects where two tolerated foods eaten together cause a reaction

References

Medical disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before making changes to your diet or discontinuing any prescribed treatments. If you suspect a true food allergy (especially one causing severe or anaphylactic reactions), seek evaluation from a board-certified allergist.