Food Intolerance Tests: What You Need to Know
- The London Allergy Clinic
- Oct 2
- 3 min read
Updated: Oct 3
What’s the difference between food allergy vs food intolerance?
Many people use “allergy” and “intolerance” interchangeably, but they are distinct. A food allergy involves your immune system reacting (often via IgE antibodies) to a normally harmless food protein.
Food intolerance, by contrast, does not involve the immune system—it’s usually a delayed reaction, dose-dependent, often affecting digestion (e.g. lactose intolerance). The British Society for Allergy and Clinical Immunology (BSACI) states, "Food allergy and intolerance are not interchangeable terms.”
For clarity, the following are common points of confusion:
- Lactose intolerance is not an allergy and will not show on an allergy test.
- Gluten intolerance is also not an allergy and will not show on an allergy test.
Milk allergies and wheat allergies do arise, but they are not the same as lactose intolerance or gluten intolerance.
Coeliac disease is also not an allergy, and will not show on an allergy test.
Recognised allergy tests: IgE, skin prick, and oral challenge
There are validated, evidence-based tests for diagnosing food allergy. For immediate (IgE-mediated) reactions, clinicians use skin prick testing or specific IgE blood tests as first-line assessments.
Positive results must always be interpreted alongside the clinical history, because sensitisation (positive test without symptoms) is common.
The true “gold standard” remains the oral food challenge, where the patient is exposed to the suspected food under careful medical supervision to see whether symptoms occur
Is there is no reliable test for food intolerance?
Unlike food allergy, no validated laboratory test exists for most forms of food intolerance or non-immune mediated food hypersensitivity.
As BSACI warns, "Alternative testing has no proven benefit in the diagnosis of food allergy and food intolerance. This may endanger patients via misdiagnosis.”
Read more here: https://www.bsaci.org/wp-content/uploads/2020/02/Choosing-wisely-ALTERNATIVE-TESTS.pdf
Diagnosing intolerance (for example lactose or fructose intolerance) is typically based on symptom history, tolerance testing (e.g. hydrogen breath tests for lactose), and controlled dietary trials.
IgG testing, “hair analysis” or other alternative tests are not clinically used and are not considered reliable.
The problems with IgG food intolerance testing
One of the most common “tests” marketed to patients is IgG food antibody testing. But this is scientifically flawed: The BSACI notes that “the presence of IgG antibodies does NOT indicate an allergy or intolerance to a specific food. IgG antibodies to food are formed in all healthy asymptomatic people.”
The British Dietetic Association (BDA) also states there is no convincing evidence to support the use of IgG testing as a diagnostic tool. Such tests can generate misleading results, causing patients to exclude many foods unnecessarily.
Risks of unnecessary elimination diets
Removing foods from your diet without a clear, evidence-based reason carries real risks. Nutritional deficiencies can result, especially in children.
Moreover, if a patient does have a genuine allergy, strict elimination over time may reduce their tolerance and increase the risk of a more severe reaction when re-exposed. Inappropriate elimination diets can also increase anxiety, social burden, and the cost and complexity of meals.
How to choose wisely: evidence-based evaluation
When suspecting a reaction to food, the correct approach is a detailed clinical history by a qualified allergy professional, focusing on timing, symptoms, dose relation, and reproducibility. Then validated tests (IgE / skin prick) can be ordered when indicated.
Alternative or “novel” tests like hair analysis, kinesiology, bio‐resonance, Vega testing, atopy patch tests, leucocyte cytotoxic tests, and others “are not valid diagnostic tests for any type of food allergy.” BSACI
How we can help at the London Allergy Clinic
At the London Allergy Clinic, we don’t sell gimmicks. We provide evidence-based evaluation: clinical assessment, validated allergy testing when appropriate, and structured challenge-based diagnosis. If you’ve tried an intolerance test and are left confused or restricted, we can help you re-establish clarity, restore nutritional balance, and guide you safely.
Our team of expert professionals can guide you through this process.
Next Steps
If you are concerned about allergy, it is advisable to seek a specialist advice and appropriate testing.
Our team at The London Allergy Clinic is available to advise on diagnosis, testing and management.
Contact us to arrange an appointment.
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