Food allergies are characterized by hypersensitivity to food products and the development of food intolerance symptoms caused by the reaction of the immune system.
It is well known that the mechanisms of food intolerance are very diverse. Reactions to foods having an allergic nature, are much less common than many people think.
Food allergies usually first develops in childhood.
Among people with diseases of the gastrointestinal tract and biliary system prevalence allergies to foods is higher than among those who do not suffer from these diseases (Nogaller A. 1983).
Among the reactions of intolerance to food can distinguish reactions to food with toxic and non-toxic in nature.
toxic reactions develop after the ingestion of foods containing as impurities toxic substances. Manifestations of these reactions and their degree of severity depend on the dose and the toxic properties of chemical compounds, rather than on the type of food product.
Among non-toxic reactions on food are two main types of intolerance to differing mechanisms of development:
1) reaction to the food, resulting in the immune system disorders (food allergy),
2) the reactions are not immunological character (food intolerance).
Food intolerance may occur in diseases of the gastrointestinal tract, biliary system, the endocrine disease, congenital and acquired enzymopathies and other diseases not associated with disturbances in the system Immunity.
In normal operation of the gastrointestinal tract and biliary system allergy to foods is not developed.
Important in the formation of hypersensitivity to foods has a genetic predisposition to allergies.
Studies have shown that about half of the patients who suffer from food allergies, there is a strong family or personal allergic history.
This means that either they themselves suffer from any allergies (pollen disease, atopic bronchial asthma) Or suffer the immediate families (parents, brothers, grandparents, etc.).
Formation of allergies in children
Forming food allergies contribute to eating disorders in women during pregnancy and lactation (Abuse of certain foods have a pronounced allergenic activity: fish, eggs, nuts, milk, etc.).
Aggravating factors in the development of the disease are
- early transfer of the child on artificial feeding;
- eating disorders in children, manifested in the disparity between the amount and ratio of food ingredients the weight and age of the child;
- concomitant diseases of the gastrointestinal tract,
- diseases of the liver and biliary tract and others.
Normal digestion and absorption of food is provided by the state of the endocrine system, the structure and function of the gastrointestinal tract, biliary system, the composition and amount of digestive juices, the composition of the intestinal microflora, the state of the local intestinal mucosal immunity (lymphoid tissue, secretory immunoglobulin and t. d.) and other factors.
Normally foods cleaved to compounds not having allergenic properties, and the intestinal wall is impermeable to the uncleaved products.
Causes of adults
The development of food allergy is triggered by common factors in adults and children.
- The first is to increase the permeability of the intestinal wall, which is observed in inflammatory diseases of the gastrointestinal tract.
- Violation (reduction or acceleration) of food intake compounds may be due to a violation of the digestion stages with insufficient pancreatic function, enzyme deficiency, biliary dyskinesia and intestines and others.
- Disorderly nutrition, rare or frequent meals lead to a breach of gastric secretion and the development of gastritis and other disorders caused by the formation of a food allergy or pseudoallergic.
- The formation of hypersensitivity to food protein nature affects not only the amount of ingested food and diet violations, but also the acidity of gastric juice (angle A. 1985).
The basis of true allergic reactions to foods is increased sensitivity and the immune response to repeated administration of a food allergen. When food enters the body first, then get into the bloodstream of food antigens, in response to which the body begins to synthesize antibodies belonging to the class of immunoglobulin A. In a healthy person the absorption of food and the supply of the antigen in the bloodstream it provides "Indifferent" of the immune system when it subsequently enters the body, and this process is under genetic control.
Food allergies can occur with a genetic predisposition to the formation of an allergy to food antigens with antibodies of immunoglobulin class E.
Sometimes it may develop an allergy to certain food additives, especially azo-dyes (particularly tartrazine).
Often the cause of pseudo-reaction to foods is not the product itself, and Various chemical additives introduced to improve the taste, odor, color and duration to ensure Storage. To the category of food additives comprise a large group of substances: dyes, fragrances, antioxidants, emulsifiers, enzymes, thickening agents, bacteriostatic agents, preservatives and others.
Among the most common food colorants may be mentioned tartrazine, providing an orange-yellow coloring product; sodium nitrite, in preserves red meat products, and others. For preservation using sodium glutamate, salicylates, specifically aspirin, and others.
Vasoactive amine - betafeniletilamin contained in chocolate products in undergoing fermentation (e.g., cheese) fermented cocoa beans, causes pseudoallergy reaction.
Manifestations of food allergies
Manifestations of the disease are varied in shape, location, severity and prognosis.
The earliest and typical manifestation of a true food allergy is to develop oral allergy syndrome. It is characterized by the appearance of itching of the mouth, numbness and / or feeling of "fullness" of the language, hard and / or soft palate, swelling of the oral mucosa after consuming food culprit allergen.
The most common gastrointestinal manifestations of the disease include:
- loss of appetite
- allergic enterocolitis.
Vomiting in food allergy may arise during a few minutes to 4-6 hours after ingestion, most patient vomits eaten food. Sometimes vomiting takes persistent character. Vomiting occurs mainly due to the reduction of the gatekeeper in contact with a food allergen in the stomach.
Allergic colicky abdominal pain may occur immediately after a meal or after a few hours and are caused by spasm of smooth muscle of the intestine. Abdominal pain are usually pronounced. Abdominal pain with food allergies may not be as intense, but persistent, are accompanied by loss of appetite, presence of mucus in the stool, and other disorders.
Anorexia may be selective with respect to the cause-significant food allergen or there may be a total loss of appetite. Constipation with food allergies are caused by spasm of smooth muscles of the different parts of the intestine.
Frequent, loose stools, appearing after ingestion cause significant food allergen, is one of the most common food allergy symptoms in both adults and children. Very often diarrhea is observed with food allergies to milk.
Allergic enterocolitis in this disease is characterized by sharp abdominal pain, presence of flatulence, Loose stools with mucus discharge of the vitreous. Patients with allergic enterocolitis complain of severe weakness, loss of appetite, headache, dizziness.
Cutaneous manifestations or allergodermatoses, food allergies spread most widely, both in adults and in children.
the most characteristic skin manifestations for true food allergies are
- atopic dermatitis.
Allergic rhinitis at disease characterized by the appearance of abundant runny nose, nasal congestion and sometimes nasal breathing difficulty.
Symptoms of food allergy in infants
Children up to year one of the first signs of the disease may be
- persistent diaper rash with careful skin care,
- appearance around the anus dermatitis and pruritus around the anus arising after feeding.
Localization of skin changes is different, but often they first appear on the face, and then can be distributed across the surface of the skin. In early disease in food allergy revealed a clear relationship with skin exacerbations reception prichinnoznachimyh food allergen, but eventually allergic skin changes become persistent nature and is constantly recurrent course, which makes it difficult to determine the cause factor a.
The diagnosis of food allergy in all the above cases, established on the basis of the inspection and survey of the patient, as well as the results of a specific Allergy examination with food allergens, and complete disappearance of the manifestations of food allergy after the appointment of elimination (ie not containing allergens) diet.
Often under the guise of hidden food allergy diseases of the gastrointestinal tract or acquired fermentopathy, worm infestation, mental illness and others.
Cytological smears (fingerprint) with mucosal (nasal cavity, conjunctiva, sputum, etc). represents available test to indirectly specify the nature of the reaction (allergic, infectious or another).
Skin tests with food allergens should always be included in the plan of examination of patients with food allergy.
Provocative tests are considered to be the most reliable methods of diagnosing allergies. Given that these tests can lead to the development of severe systemic reactions, they are recommended only in inpatient or outpatient basis in allergological study, based on the existing general hospital with an intensive therapy.
Two weeks prior to the provocative test is assigned a diet with exception of the alleged causal food allergens. Provocation test carried out in the morning on an empty stomach, with the overall good health of the patient. As a food allergens can be used dry or freeze-dried foods (milk powder, egg powder, flour, nuts, meat and the like. D.). The estimated food allergen (8 mg) was enclosed in a capsule (e.g., gelatin), allowed the patient to swallow, and then within 24 hours of being watched, fixing the subjective and objective indicators: complaints, the state of the skin and mucous membranes, fluctuations in blood pressure, heart rate and et al.
If within 24 hours of food allergy symptoms did not appear, the test is repeated the next day, but the dose of allergen is increased to 20 mg. If negative, the test is repeated the next day, each time doubling dose administered dry food product, gradually bringing it up to 8000 mg, corresponding to 100 g of raw food product. If after administration of 8000 mg food allergen reaction is not followed, testing is stopped and consider that the test product is not a food allergen in a particular patient.
Young children who can not swallow the capsule, food allergies can be added to food. Scheme of provocation tests in children is the same as in adults, but the dose administered food allergens ranges from 8 mg to 2000 mg.
If food allergy signs of intolerance usually occur within 2-12 hours after administration of a provocative food product: skin rash, gastrointestinal symptoms, etc... Provocative tests are not assigned to those products that can cause severe systemic reactions. The method of "gemokod" can not be used to diagnose a true food allergy, since it fails to identify the specific allergic antibodies to foods. Among the most informative studies to identify food allergies are:
- radioallergosorbent test (RAST);
- immunosorbent assay (ELISA);
- test using SAR-system, MAST-CLA-system.
Treatment of food allergies
The basic principles of treatment of food allergies are integrated approach and stages in carrying out therapy aimed at eliminating both of allergy symptoms, and for the prevention of exacerbations. Of key importance is the appointment of an adequate good nutritionCorresponding to the volume ratio of the food ingredients and the patient's age, his weight, concomitant somatic disease and other factors.
When a true food allergy, as in any other allergic diseases, apply specific and non-specific treatments. Non-specific therapies aimed at eliminating the symptoms of established disease and for prevention of exacerbations.
In acute manifestations common food allergy antihistamines I generation (Tavegilum, Suprastinum) is administered orally in tablet form.
When manifestations of mild to moderate severity usually used antihistamines of the new generation:
- ebastine (Kestin)
- cetirizine (Zyrtec, allertek, Letizen S et al.),
- fexofenadine (telfast)
- Loratadine (Claritin, klarisens et al.).
When a food allergy doctor must prescribe enterosorbent Enterosgel course for the removal of allergens. The drug gel is saturated with water. He gently envelops the mucous membranes of the gastrointestinal tract, collects them and allergens out of the body. Enterosgelya important advantage is that the allergens firmly bonded with the gel and are not released into the intestinal hotel located below. Enterosgel as a porous sponge absorbs harmful substances mainly without interacting with the useful microflora and trace elements, so it can take more than 2 weeks.
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Specific treatments for food allergy include the exclusion of food allergens and Asit (allergen specific immunotherapy).
Exclusion from the diet cause and a significant food allergen refers to the basic methods of treatment of food allergies, and when she develops rarely used for food products (e.g., strawberry, chocolate, crabs and m. n.) it can be recognized only effective treatment.
The diet requires the exclusion from the diet not only specific food responsible for the development of food allergies, but also any other, to which it is part, even in trace amounts.
In appointing the diet is necessary to strictly follow the order to match the patient's diet by volume and the ratio of food ingredients, his weight and age.
The allergen-specific immunotherapy (ASIT) in food allergy is performed only in the case when the food is essential (for example, allergies to milk in children).
Learn more about nutrition for allergies can be read in our article "Hypoallergenic diet"