Causes of food allergy

Risk factors of food allergy. To the development of food allergies predisposes hereditary burden on allergic diseases. In patients with a hereditary burden, an increase in the incidence of antigens by HLA as B27, Bw35, Bw41. In a number of groups of patients, these antigens had a significant increase: HLA-B27 was more common in children with unhealed atopic heredity, HLA-Bw35 in patients with monovalent sensitization, and HLA-Bw41 in patients with a wide range of sensitization and unhealthy heredity.

In addition to burdened heredity, a number of other risk factors are observed in patients with food allergy. This is the use of a pregnant woman obligate allergens or foods that the mother has caused allergic reactions. Especially the excessive use of dairy products against the background of the toxicosis of pregnant women leading to changes in the mother-placenta-fetus system with increasing permeability of the placental barrier for both allergens and maternal globulins, possibly with a changed structure and related to the epithelial cover of the fetus, also sensitized lymphocytes. The risk factors for food allergies in children include the later application of the newborn to the breast (lack of secretory IgA, bifidogenic factors); early artificial feeding and non-compliance with a breast-feeding woman with a hypoallergenic diet; irrational introduction of complementary feeding to the child, deficiencies of microelements (zinc, selenium, copper). Promote the development of food allergies, acute and chronic inflammation of the gastrointestinal tract; intestinal dysbiosis, congenital or acquired deficiency of secretory immunity.

Other risk factors for the development of food allergies:

• acute and chronic inflammation of the gastrointestinal tract, intestinal dysbacteriosis, acquired hypovitaminosis (especially often hypovitaminosis A and E and / or deficiencies in zinc, selenium, copper, carnitine, taurine);
• aggressive environmental influences: increased "aggressiveness" (contamination) of drinking water, long-term exposure to small doses of radionuclides, xenobiotics of food products of industrial canning lead to a decrease in the barrier function of the gastrointestinal tract and the disturbance of immunological regulation in general, which aggravates the violation of food tolerance;
• congenital or acquired deficiency of secretory immunity.

Causes of food allergy. In children, as a cause of the development of food allergies, the most often observed is an increased sensitivity to cow's milk - 72-76.9%. The data show that children with milk allergy were significantly more likely to get cow's milk proteins in the first three months, especially in the first month of life, and the average age of clinical symptoms of allergy to milk in patients was 2 months. IM Vorontsov and OA Matalygina noted the absence of a significant difference between the frequency of use of mixed feeding and the conditions for switching to artificial in groups of children with dairy and non-dairy allergies. There was no clear difference in the duration of the periods of mixed feeding. A sharp change in breastfeeding by artificial (for 1-2 days) was observed in 32% of children with food allergy.

A clear connection was established between the development of allergic reactions in children of the first months of life with the presence of food antigens in the milk of nursing mothers. When examined with immunoelectrophoresis, 52% of lactating women in milk had cow milk antigens. During the 8-month observation period, 65% of the children of these women were allergic to cow's milk, and only 14% among children whose mothers did not have cow milk antigens with their breast milk.

According to the results of a study by Balabolkin II (1997), specific antibodies to bovine milk in children with gastrointestinal food allergy are detected by immunoenzymatic method in 85% of antibodies to alpha-lactoglobulin (61%), beta-lactalbumin (43%), bovine serum albumin (37%), casein (57%).

According to research, sensitivity to chicken eggs was detected in 59% of children with food allergy, to fish - in 54%, to wheat - in 39%. In children with gastrointestinal food allergy, according to the enzyme immunoassay, specific IgE to chicken eggs was determined in 97%, to fish - in 52.9%, beef - in 50%, rice - 47%, chicken meat - in 28.6% .

In children from 6 months to 3 years, according to research, food allergy is noted in 36% of buckwheat, 11.5% in corn, 50% in apples, 32% in soybean, in 45% in bananas; in 3% to pork, 2% to beef, and turkey - 0%.

Chicken eggs contain several antigenic components: ovalbumin, ovomucoid, ovomucin in protein and vitellin in yolk. When cooking eggs, their activity decreases, so the steep yolk and protein have less allergic activity. It should be borne in mind that in children with increased sensitivity to chicken eggs, an allergic reaction to vaccinations with vaccines containing an admixture of tissues of a chicken embryo is possible.

The most powerful allergenic effect is provided by lactoglobulin of cow's milk. It is noted that whole cow milk causes an allergic reaction more often than sour milk or undergoing other treatment (boiling, drying, etc.). Increased sensitivity to cow's milk can manifest itself in children on artificial feeding in the first months of life. Allergic reactions to vegetables (carrots, tomatoes), fruits (oranges, red apples, bananas), berries (strawberries, black currants, strawberries) can be associated with both protein and non-protein components. Symptoms of allergies can be manifested as a result of the intake of exogenous histamine with vegetables and berries. With the intake of certain foods, processes that lead to direct liberation of the biologically active substances of mast cells and basophils can develop.

The younger the child, the higher the permeability of his intestine for food antigens. With age, especially after 2-3 years, with a decrease in intestinal permeability, a decrease in the level of antibodies to food proteins is determined.

Pathogenesis of food allergy. Reduction of systemic exposure to foreign antibodies provides immune and non-immune barrier systems of the digestive tract.

Non-immune include gastric acid secretion of hydrochloric acid and proteolytic enzymes that break down proteins to less antigenic molecules by reducing their size or changing the structure. Physical barriers (production and secretion of mucus, peristalsis) reduce the duration and intensity of contact of potential allergens with the gastrointestinal mucosa. The preserved epithelium of the intestine prevents the absorption of macromolecules.

The gastrointestinal tract has a kind of immune system - the lymphoid tissue associated with the intestine, consisting of discrete clusters of lymphoid follicles; intraepithelial lymphocytes, plasmatic and mast cells of the intrinsic layer of the mucosa; mesenteric lymph nodes.

The formation of tolerance (from Latin tolerantia - patience, endurance) to food is provided by factors of local and systemic immunity.

In the intestine, the antigen is converted into a non-allergenic (toleogenic) form. This form of allergen has minor structural differences from the original, which causes suppression of the cellular immune response by stimulation of CD8 + T cells.

Food allergy develops in children susceptible to allergy due to lack of tolerance to food allergens or its loss, which can be caused by many reasons:

• functional immaturity of the immune system and digestive organs;
• The production of Ss IgA and CD8 + T cells is smaller in comparison with adults;
• a lower production of hydrochloric acid and a lower activity of digestive enzymes;
• less mucus production.

All of these factors contribute to increased contact of food antigen with the cells of the immune system of the intestine, which leads to hyperproduction of specific antibodies with the subsequent development of hypersensitivity.

The development of atopic reaction on the mucous membrane of the gastrointestinal tract enhances its permeability and increases the passage of food allergens into the bloodstream. Food allergens can reach separate organs (lungs, skin, etc.) and activate mast cells there. In addition, the BAS produced in the pathophysiological stage enters the bloodstream and can also determine remote reactions outside the gastrointestinal tract.

Isolated immune mechanisms of allergic reactions (reactive, cytotoxic, immunocomplex, delayed-type hypersensitivity) are rare. In the majority of patients with food allergy, their various combinations develop over time. A significant role in the mechanism of food allergy is played by delayed hypersensitivity, in which the elimination (lysis) of antigens is carried out directly by lymphoid cells.

Various mechanisms of pseudoallergia can occur parallel to the current atopic reaction or exist independently of it. In this case, the release of biologically active substances from mast cells occurs without the participation of the immunological stage, although the clinical manifestations differ little from the usual reaction reactions. Probably, therefore, in 30-45% of children with food allergy the level of IgE in the blood is normal.

Parallergic phenomena are typical for the syndrome of "instability of cell membranes", the genesis of which is extremely wide: excess in the supply of xenobiotics and intranents (various additives in the industrial canning of food), the use of fertilizers (sulfites, alkaloids), hypovitaminosis and micronutrient deficiencies. The syndrome of "instability of cell membranes" is formed and aggravated in chronic diseases of the gastrointestinal tract, dysbacteriosis, is typical for children with exudative-catarrhal and lymphatic-hypoplastic anomalies of the constitution.

[1], [2], [3], [4], [5]