Diagnosis of food allergy
Last reviewed: 23.04.2024
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Food allergies are diagnosed primarily on the basis of anamnestic data.
When conducting a differential diagnosis of a true food allergy from other types of food intolerance should be taken into account.
- the amount of product required for the reaction;
- type of suspected food product;
- reaction to past use of the product;
- the interval between the use of the product and the development of the reaction (IgE-mediated reactions appear within 2 hours after ingestion);
- clinical manifestations, characteristic of food allergies;
- the disappearance of symptoms on the background of elimination of the product and their appearance after its introduction;
- duration of symptoms;
- medicines needed to stop the reaction.
The answer to all these questions can be obtained by long-term maintenance of a food diary.
Informative-provocative tests are informative. Elimination of the suspect product is carried out within 7-14 days. Against the background of the improvement in the condition caused by the elimination diet, the patient is prescribed to take an eliminated product and assess the condition within 24-48 hours under the supervision of the doctor, since strong systemic reactions are possible.
The gold standard in the diagnosis of food allergy is a double-blind provocative test using a placebo.
Skin tests with allergens in food allergies are less informative than with inhalation sensitization, and should be interpreted only in conjunction with anamnesis and clinical manifestations of food allergies.
Of the possible diagnostic tests in vitro, the most informative are:
- detection of specific IgE antibodies to various allergens by radioallergosorbent or immunoenzymatic tests;
- degranulation of mast cells in rats;
- reaction leukocytolysis, inhibition of migration of leukocytes with food allergens.
Differential diagnosis of food allergy is carried out with skin, gastrointestinal, respiratory tract of non-allergic etiology.
General criteria for diagnosis of allergic diseases. Allergic diseases have common diagnostic criteria. This is primarily the data of an allergic anamnesis. Presence of hereditary predisposition makes the diagnosis of an allergic disease more likely. It should be noted that not only the allergic predisposition is inherited, but also the localization of the "shock area", and patterns in combination and alternation of allergic symptoms. Of great importance in the diagnostic plan is the identification of reactions to ongoing preventive vaccinations, manifestations of drug allergy in diseases. Diagnostic significance has an acute onset and rapid development of the process, as well as a sudden and rapid termination of the reaction; repetition of symptoms under similar circumstances, polymorphism of the clinical picture and vivid expression of individual symptoms. The effect of eliminating the allergen and the results of specific diagnostics (skin and provocative tests), eosinophilia in the blood and pathological secrets are of great diagnostic importance.
Diagnosis is based on using the results of skin testing and performing provocative tests with suspected allergens, if necessary. However, much more important is the diagnosis in vitro: radioallergosorbent test, radioimmunosorbent, immuno-immunogenic methods. The reaction of passive hemagglutination, blast transformation of leukocytes (RBTL), neutrophil damage index, determination of IgE and circulating immune complexes (CEC) is determined. Radioimmunosorbent test allows to detect elevated levels of IgE, which indicates an allergic mood of the body. The radioallergosorbent test allows to determine in the blood of the child specific reactive antibodies to food allergens. It is shown that the simultaneous detection of IgE and RBTL with food allergens allows to significantly increase the diagnostic capabilities of laboratory methods for food sensitization in patients with atonic dermatitis and to effectively predict allergic diseases in children while examining these parameters in cord blood.
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