Are immunoglobulin G (IgG) tests reliable for detecting allergies or intolerances to certain foods? Many clinics, laboratories and centers offer this type of test to determine sensitivity to a multitude of foods, usually between 100 and 200, simultaneously. The price can reach 200 euros but, are they really worth it?

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As reported by the Organization of Consumers and Users (OCU), these tests they have “no scientific basis to support the relationship between the presence of IgG and these alleged food sensitivities”. IgGs are soluble proteins that are part of our immune system and serve as a defense against the action of certain external pathogens that can cause diseases.

However, allergies are detected through antibodies called immunoglobulin E (IgE), which are responsible for reacting to substances that it detects as a threat to the body such as pollen. “In allergy sufferers, B lymphocytes recognize as harmful proteins of innocuous external agents such as pollen, dust mites, food, etc., it is then that the IgE are produced that trigger an entire immune reaction”, adds the OCU.

Do these tests offer reliable results?

For this reason, allergy tests look for the different levels of IgE that a person has against the elements responsible for the allergy. Conversely, IgG tests do not have any scientific and medical evidence to indicate intolerance or sensitivity towards certain foods.

The Public Health Commission has approved this Tuesday, September 22, the use of antigen tests as a rapid diagnostic and screening tool for Covid-19 and has updated the Strategy for early detection, surveillance and control to include this test with the objective to face the coronavirus pandemic, as they have assured in a statement.
What are antigenic tests and how are they used?

First of all, it is important to differentiate allergy from food intolerance. An allergic reaction “it is all that alteration caused in the basal state of the organism by exposure to an allergen “, stand out from the Andalusian Society of Digestive Pathology. On the other hand, food intolerance “is a non-immunologically mediated disorder”.

So, If a person has an intolerance or sensitivity, it is because “the body is not processing or digesting food properly“, they underline in the American Academy of Allergy, Asthma and Immunology (AAAAI). One of the most frequent among the population is lactose intolerance, which causes stomach pain, gas, diarrhea or flatulence.

Currently, many private health centers, pharmacies, insurance companies or laboratories offer food intolerance tests by detecting IgG antibodies. However, “It has never been scientifically proven that this evaluation can achieve what it claims. The presence of IgG is probably a normal response of the immune system to food exposure “, they add from the AAAAI.

What consequences can they have for patients?

The Spanish Society of Allergology and Clinical Immunology (SEAIC) it also warns of the harmful consequences in patients and urges “not to perform diagnostic tests of doubtful efficacy, such as immunoglobulin G, or an indiscriminate battery of IgE to allergens in the study of allergies.”

These tests can be misleading to patients and lead to “unnecessary, ineffective and in most cases harmful treatments“, indicate the experts of the Andalusian Society of Digestive Pathology.

In fact, a restriction or elimination of certain foods can occur, leading to significant nutritional deficiencies. Psychological imbalances could also be produced by increasing the state of anxiety and tension when faced with more restrictive diets.