Food Intolerance & Allergy Tests: IgE, IgG & the Scientific Perspective

What scientific evidence says about intolerance and allergy tests

Reactions to foods have very different causes – and accordingly require different diagnostics. An allergy is an immune-system reaction, usually involving IgE antibodies. An intolerance is generally a metabolic or enzymatic issue, as with lactose, and has nothing to do with the allergic IgE system. This distinction is the basis of any sound assessment.

Blood tests determine specific antibodies for this purpose. Specific IgE shows whether allergic sensitization to an allergen is present; the European professional society EAACI describes in its guideline how such values should be interpreted [1]. IgG antibodies against foods, on the other hand, often only reflect what the immune system has been exposed to – they are considered signs of exposure and tolerance, not disease [2].

This page explains what IgE and IgG tests measure, how true intolerances (e.g., lactose intolerance, celiac disease) are correctly diagnosed, how the sample is processed, and where the scientific limitations lie. The aim is an honest, verifiable assessment – not a promise of a cure.

Tests and markers at a glance

Important: An antibody level is a laboratory finding, not a diagnosis. It must always be assessed in the context of symptoms and medical evaluation.

The markers in detail

Allergy or intolerance? The key distinction

In an allergy, the immune system reacts—often with IgE antibodies—to a substance that is harmless in itself. An intolerance, by contrast, usually occurs without an allergic reaction, for example because an enzyme is missing (lactase in lactose intolerance) or a substance is poorly absorbed. Both may feel similar to those affected, but they require different tests. A single blood test does not identify all causes.

Specific IgE: sensitization is not the same as allergy

An IgE test shows whether the body is sensitized to an allergen. Many people have detectable IgE without developing symptoms upon contact. Only when measurable IgE and corresponding symptoms occur together is it considered an allergy; the EAACI guideline describes this relationship and the role of medical assessment [1].

IgG against foods: what the result means—and what it does not

IgG antibodies against foods develop as a normal response to contact with food and are associated more with tolerance than with intolerance. An EAACI position paper and the German medical society guideline consistently conclude that IgG/IgG4 testing against foods is not suitable for diagnosing intolerances [2][3]. At most, an IgG result can provide a structured starting point for a professionally supervised elimination and reintroduction trial—and nothing more.

True food intolerances: lactose, fructose, histamine

Lactose intolerance is caused by reduced activity of the enzyme lactase; the genetic predisposition (MCM6/LCT) was described by Enattah and colleagues [4] and can also be assessed with an H2 breath test. Fructose malabsorption and histamine intolerance likewise have their own established diagnostic pathways. None of these intolerances is diagnosed using an IgG food test.

Celiac disease: a distinct, clearly defined diagnostic process

Celiac disease is an immune-mediated condition caused by gluten—but it is not a classic allergy. According to guidelines, it is diagnosed using specific antibodies (transglutaminase IgA), genetic markers HLA-DQ2/DQ8 where appropriate, and a small-intestinal biopsy [5]. Important: For meaningful results, gluten must not be eliminated before the evaluation. An IgG food test does not replace this diagnostic process.

Privacy, methodology & quality

Data protection & data processing: Protecting your data is our top priority. Under the General Data Protection Regulation (GDPR), health data are among the specially protected categories of personal data (Article 9 GDPR). At mybody®, they are processed for a specific purpose—exclusively to perform and evaluate your test—and on the basis of your consent. They will not be processed for other purposes without your consent.

Information security is organized in accordance with ISO/IEC 27001, the internationally recognized standard for information security management systems. Your data is transmitted and stored in encrypted form. You have the data subject rights under the GDPR—particularly the right to access, correct, and delete your data. Details regarding storage periods, processing, and your rights are set out in the privacy policy.

The sample is collected at home as capillary blood from a fingertip prick. In the laboratory, the antibodies (specific IgE or IgG) are measured using established immunological methods. The results are interpreted against the ranges shown in the report; their significance only emerges in conjunction with symptoms and professional assessment.

1. 1

   Collect the sample

   Capillary blood collected at home via a fingertip prick (test kit including instructions).

2. 2

   Return shipping

   Free return shipping to the analytical laboratory.

3. 3

   Laboratory analysis

   Measurement of antibodies (specific IgE or IgG).

4. 4

   Laboratory report

   Preparation of the report and provision through the online portal.

5. 5

   Result

   Usually 3–5 working days after receipt of the sample.

Laboratory & accreditation: The analysis is performed in a medical specialist laboratory accredited according to DIN EN ISO 15189:2024 (MVZ GANZIMMUN GmbH, Mainz; DAkkS registration number D-ML-13151-01-00) [6]. The laboratory participates in external proficiency testing schemes (including INSTAND e.V., Referenzinstitut für Bioanalytik/RfB, UK NEQAS, ERNDIM). Accredited refers to the assessment of the technical and professional competence of the analysis by the German Accreditation Body (DAkkS) [7] and must be distinguished from certified (management system, e.g. ISO/IEC 27001). Accreditation concerns the accurate measurement of the laboratory value—not whether a test concept is clinically suitable for diagnosis.

Frequently asked questions

Sources

1. Santos AF et al. EAACI guidelines on the diagnosis of IgE-mediated food allergy. Allergy 2023;78(12):3057–3076. Allergy (EAACI)
2. Stapel SO et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy 2008;63(7):793–796. PubMed
3. Kleine-Tebbe J et al. No recommendation for IgG and IgG4 testing against foods (DGAKI/ÄDA/GPA guideline). Allergo J 2009. Guideline (PDF)
4. Enattah NS et al. Identification of a variant associated with adult-type hypolactasia (lactase persistence, MCM6/LCT). Nature Genetics 2002;30:233–237. PubMed
5. German Society for Gastroenterology (DGVS). S2k Guideline on Celiac Disease, AWMF Reg. No. 021-021, as of 2022. register.awmf.org
6. MVZ GANZIMMUN GmbH. Quality management – accreditation according to DIN EN ISO 15189:2024 (DAkkS D-ML-13151-01-00). ganzimmun.de
7. DAkkS – Medical Laboratories / DIN EN ISO 15189 (accreditation explanation). dakks.de