Food allergies are characterized by an increased sensitivity of the body to food and the development of signs of food intolerance caused by the reaction of the immune system.
It is well known that the mechanisms of food intolerance are very diverse. Reactions to food that are allergic in nature are much less common than many people believe.
Food allergies, as a rule, develops for the first time in childhood.
Among people with diseases of the gastrointestinal tract and biliary system, the prevalence of food allergy is higher than among those not suffering from these diseases ( Nogaller A., 1983).
Among the reactions of food intolerance can be distinguished reactions to food, having a toxic and non-toxic nature.
Toxic reactions develop after eating foods containing toxic substances as impurities. The manifestations of these reactions and their severity depend on the dose and chemical properties of toxic compounds, and not on the type of food product.
Among non-toxic reactions There are two main types of intolerance for food, differing in developmental mechanisms:
1) reactions to food products caused by disorders in the immune system (food allergies),
2) reactions are not immunological in nature (food intolerance).
Food intolerance can develop in diseases of the gastrointestinal tract, biliary system, endocrine pathology, congenital and acquired enzymopathies and other diseases not associated with impairments in the immune system.
In the normal functioning of the gastrointestinal tract and biliary system allergy to food does not develop.
The genetic predisposition to allergies is important in the formation of hypersensitivity to food.
Studies have shown that about half of patients suffering from food allergies, there is a burdened family or own allergic history.
This means that either they themselves suffer from any allergic diseases ( pollinosis, atopic bronchial asthma ), or their closest relatives (parents, brothers, grandmothers, etc.) suffer.
The formation of allergies in childhood
Formation of food allergies contribute to eating disorders in women during pregnancy and feeding (abuse of certain products that have a pronounced allergenic activity: fish, eggs, nuts, milk, etc.).
Provocative factors for the development of the disease are
- early transfer of the child to artificial feeding;
- eating disorders in children, expressed in the discrepancy between the volume and ratio of food ingredients to the weight and age of the child;
- associated diseases of the gastrointestinal tract,
- diseases of the liver and biliary tract, etc.
Normal digestion and absorption of food is provided by the state of the endocrine system, the structure and function of the gastrointestinal tract, the biliary system, the composition and volume of digestive juices, the composition of the intestinal microflora, the state of local immunity of the intestinal mucosa (lymphoid tissue, secretory immunoglobulins, etc.), and other factors.
Normally, food products are split into compounds that do not have allergenic properties, and the intestinal wall is impermeable to unsplit products.
Causes in adults
The development of food allergies is triggered by common factors for adults and children.
- The first is the increase in the permeability of the intestinal wall, which is observed in inflammatory diseases of the gastrointestinal tract.
- Violation (reduction or acceleration) of the absorption of food compounds may be due to a violation of the digestion stages with insufficient pancreatic function, enzyme deficiency, biliary dyskinesia and intestines, etc.
- Indiscriminate nutrition, rare or frequent meals lead to impaired gastric secretion, the development of gastritis and other disorders causing the formation of food allergies or pseudo- allergies .
- The formation of increased sensitivity to food products of protein nature is influenced not only by the amount of food taken and dietary disorders, but also by the acidity of the gastric juice ( Ugolev A., 1985).
The basis of the true allergic reactions to food is the increased sensitivity and immune response to the reintroduction of the food allergen. When a food product enters the body for the first time, food antigens enter the bloodstream, in response to which antibodies of the immunoglobulin A. class begin to be synthesized in the body. In a healthy person, absorption of the food antigen and its entry into the bloodstream provides an “indifference” of the immune system when its subsequent entry into the body, and this process is under genetic control.
Food allergies can develop with a genetic susceptibility to the formation of an allergy to food antigens with the participation of antibodies of the immunoglobulin class E.
Allergies can sometimes develop to some food additives, especially azo- dyes (in particular, tartrazine ).
Often the reason for the development of a pseudo-allergic reaction to food is not the product itself, but various chemical additives introduced to improve the taste, smell, color and ensure the duration of storage. A large group of substances belongs to the category of food additives: colorants, flavors, antioxidants, emulsifiers, enzymes, thickeners, bacteriostatic substances, preservatives, etc.
Among the most common food colorings can be mentioned tartrazine, providing orange-yellow staining of the product; sodium nitrite, preserving the red color of meat products, and others. For preservation, monosodium glutamate, salicylates, in particular acetylsalicylic acid, etc. are used.
Vazoaktivny amine – betaphenylethylamine, contained in chocolate, in products undergoing fermentation (for example, cheeses), fermented cocoa beans, causes pseudo-allergic reactions.
Manifestations of the disease are diverse in form, location, severity and prognosis.
The earliest and most typical manifestation of true food allergy is the development of the oral allergic syndrome. It is characterized by the appearance of itching in the mouth, numbness and / or a feeling of “bursting” of the tongue, hard and / or soft palate, swelling of the oral mucosa after eating the guilty food allergen.
The most frequent gastrointestinal manifestations of the disease include:
- loss of appetite
- allergic enterocolitis.
Vomiting in food allergies can occur over a period of from several minutes to 4-6 hours after eating, more often the patient vomits eaten food. Sometimes vomiting takes persistent nature. The occurrence of vomiting is mainly associated with a reduction in the pylorus when a food allergen is ingested into the stomach.
Allergic colicky abdominal pain can occur immediately after a meal or after a few hours and is caused by a spasm of the smooth muscles of the intestine. Abdominal pain are usually pronounced. Abdominal pain in food allergies may not be as intense, but persistent, accompanied by a decrease in appetite, the presence of mucus in the stool and other disorders.
Lack of appetite may be selective in relation to the cause-significant food allergen or there may be a general decrease in appetite. Constipation with food allergies caused by spasm of smooth muscles of different parts of the intestine.
Frequent, loose stools that appear after taking a cause-significant food allergen is one of the most common signs of food allergy in both adults and children. Especially often diarrhea occurs in food allergies to milk.
Allergic enterocolitis with this disease is characterized by severe abdominal pain, the presence of flatulence , loose stools with discharge of vitreous mucus. Patients with allergic enterocolitis complain of severe weakness, loss of appetite, headache, dizziness.
Skin manifestations, or allergic dermatosis , with food allergies are most common, both in adults and in children.
For true food allergies, the most characteristic skin manifestations are
- Quincke’s edema
- atopic dermatitis.
Allergic rhinitis when the disease is characterized by the appearance of abundant mucous- watery nasal discharge, sometimes nasal congestion and difficulty in nasal breathing.
Symptoms of food allergies in infants
In children under one year, one of the first signs of illness can be
- stubborn diaper rash with careful skin care,
- the appearance of dermatitis around the anus and itching around the anus after feeding.
Localization of skin changes is different, but more often they appear first in the face, and then can spread over the entire surface of the skin. At the onset of the disease, food allergies reveal a clear association of skin exacerbations with the intake of a causally significant food allergen, but over time, allergic changes in the skin become persistent and constantly relapsing, which makes it difficult to determine the causative factor.
The diagnosis of food allergy in all the above cases is established on the basis of examination and questioning of the patient, as well as the results of a specific allergological examination with food allergens, and with the complete disappearance of food allergy after prescribing an elimination (that is, not allergen-free) diet.
Often under the guise of food allergies hide diseases of the gastrointestinal tract or acquired fermentopathy, worm infestations, mental illness, etc.
Cytological examination of smears (prints) from mucous membranes (nasal cavity, conjunctiva, sputum, etc.) is an accessible test that allows indirectly clarifying the nature of the reaction (allergic, infectious or other).
Skin tests with food allergens should always be included in the examination plan for patients with food allergies.
Provocative tests are among the most reliable methods for diagnosing allergies. Considering that these tests can lead to the development of a severe systemic reaction, they are recommended to be carried out only in a hospital or on an outpatient basis, in an allergy room, existing on the basis of a multidisciplinary hospital with an intensive care unit.
Two weeks before the provocative test, a diet is prescribed with the exception of the alleged causative food allergens. The provocative test is carried out in the morning, on an empty stomach, against the background of the general well-being of the patient. Dry or freeze-dried foods (milk powder, egg powder, flour, nuts, meat, etc.) can be used as food allergens . Estimated food allergen (8 mg), enclosed in a capsule (for example, gelatin), is given to the patient to be swallowed, after which they are monitored for 24 hours, fixing subjective and objective indicators: complaints, condition of the skin and mucous membranes, blood pressure fluctuations, frequency heart rate, etc.
If there are no signs of food allergy within 24 hours, the test is repeated every other day, but the dose of the allergen is increased to 20 mg. In the event of a negative result, the test is repeated every other day, each time doubling the dose of the food dried food product, gradually bringing it up to 8000 mg, which corresponds to 100 g of the original food product. If, after the administration of 8000 mg of a food allergen, the reaction is not followed, the testing is stopped and the test product is considered not to be a food allergen in this patient.
Small children who cannot swallow a capsule can be added to the food allergen. The scheme of provocative tests in children is the same as in adults, but the dose of food allergens administered ranges from 8 mg to 2000 mg.
In food allergies, signs of intolerance, as a rule, appear 2–12 hours after the provocative introduction of a food product: skin rashes, gastrointestinal manifestations, etc. Provocative tests are not prescribed with those products that can cause severe systemic reactions. The hemocode method cannot be used for the diagnosis of true food allergy, since it cannot be used to detect specific allergic antibodies to food products. The most informative studies to identify food allergies include:
- radioallergosorbent test (PAST);
- enzyme-linked immunosorbent assay (ELISA);
- test using CAP- system , MAST-CLA- system.
The basic principles of food allergy treatment are an integrated approach and the phasing in the treatment, aimed at eliminating the signs of allergy and at preventing exacerbations. The appointment of an adequate rational nutrition , corresponding in terms of the volume and ratio of food ingredients to the patient’s age, weight, concomitant somatic diseases and other factors.
For true food allergies, as with any other allergic disease, specific and non-specific treatments are used. Nonspecific methods of treatment are aimed at eliminating signs of a developing disease and at preventing exacerbations.
For acute common manifestations of food allergy, antihistamines of the first generation (tavegil, suprastin) are administered orally in the form of tablets.
When manifestations of mild and moderate severity often use antihistamines of a new generation:
- Ebastine ( Kestin ),
- cetirizine ( zyrtec , allertek , letisen , etc.),
- fexofenadine ( telfast ),
- loratadine (claritin, clarisens , etc.).
When food allergies doctors must prescribe enterosorbent Enterosgel course for removing allergens. The drug is a water-saturated gel. It gently envelops the mucous membranes of the gastrointestinal tract, collects allergens from them and removes them from the body. An important advantage of Enterosgel is that allergens bind strongly to the gel and are not released in the intestinal calfs below. Enterosgel as a porous sponge absorbs mainly harmful substances without interacting with beneficial microflora and microelements, so it can be taken for more than 2 weeks.
* * *
Specific treatment methods for food allergies include exclusion of the food allergen and ASIT ( allergen- specific immunotherapy).
Exclusion from the diet of a causally significant food allergen is one of the main methods of treating food allergies, and in cases where it develops to rarely consumed food products (for example, strawberries, chocolate, crabs, etc.), it can be considered the only effective treatment. .
The diet requires exclusion from the diet not only of a specific food product, which is responsible for the development of food allergies, but also of any others, in which it is included, even in trace amounts.
When prescribing a diet, it is necessary to strictly ensure that the diet of the patient matches the volume and ratio of food ingredients, its weight and age.
The allergen-specific immunotherapy (ASIT) in food allergy is performed only in the case when the food is vital (such as allergies to milk in children).