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Diagnosis of food allergies
Last reviewed: 04.07.2025
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Food allergies are diagnosed primarily based on anamnestic data.
When conducting differential diagnostics of true food allergy from other types of food intolerance, it should be taken into account.
- the amount of product required to cause a reaction;
- type of suspected food product;
- reaction to past use of the product;
- the time interval between consumption of the product and the development of the reaction (IgE-mediated reactions appear within 2 hours after eating);
- clinical manifestations characteristic of food allergies;
- disappearance of symptoms during elimination of the product and their appearance after its introduction;
- duration of symptoms;
- medications needed to stop the reaction.
The answer to all these questions can be obtained by keeping a food diary for a long time.
Elimination-provocation tests are informative. Elimination of the suspected product is carried out for 7-14 days. Against the background of improvement of the condition caused by the elimination diet, the patient is prescribed intake of the eliminated product and the condition is assessed for 24-48 hours under the supervision of a doctor, since strong systemic reactions are possible.
The gold standard in diagnosing food allergies is a double-blind, placebo-controlled challenge test.
Skin tests with allergens in food allergy are less informative than in inhalation sensitization and should be interpreted only in conjunction with the history and clinical manifestations of food allergy.
Of the possible in vitro diagnostic tests, the most informative are:
- determination of specific IgE antibodies to various allergens using radioallergosorbent or enzyme immunoassay tests;
- rat mast cell degranulation reaction;
- leukocytolysis reactions, inhibition of leukocyte migration with food allergens.
Differential diagnosis of food allergy is carried out with diseases of the skin, gastrointestinal, and respiratory tract of non-allergic etiology.
General criteria for diagnosing allergic diseases. Allergic diseases have general criteria for diagnosing. These are primarily the data of the allergological anamnesis. The presence of a hereditary predisposition makes the diagnosis of an allergic disease more likely. It should be noted that not only allergic predisposition is inherited, but also the localization of the "shock territory" and patterns in the combination and alternation of allergic symptoms. Of great importance in diagnostic terms is the detection of reactions to preventive vaccinations, manifestations of drug allergy in diseases. Of diagnostic significance are the acute onset and rapid development of the process, as well as the sudden and rapid end of the reaction; recurrence of symptoms under similar circumstances, polymorphism of the clinical picture and the pronounced expression of individual symptoms. Of great diagnostic importance are the effect of allergen elimination and the results of specific diagnostics (skin and provocative tests), eosinophilia in the blood and pathological secrets.
Diagnostics is based on the results of skin testing and, if necessary, provocative tests with suspected allergens. However, in vitro diagnostics are of much greater importance: radioallergosorbent test, radioimmunosorbent, and immunoenzyme methods. They determine the passive hemagglutination reaction, leukocyte blast transformation (RBTL), neutrophil damage index, determination of IgE and circulating immune complexes (CIC). The radioimmunosorbent test allows detecting an elevated level of IgE, which indicates an allergic mood of the body. The radioallergosorbent test allows determining specific reaginic antibodies to food allergens in the child's blood. It has been shown that the simultaneous determination of IgE and RBTL with food allergens can significantly increase the diagnostic capabilities of laboratory methods in food sensitization in patients with atopic dermatitis and effectively predict allergic diseases in children with a simultaneous study of these indicators in umbilical cord blood.
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