Pseudoallergy is an increased reactivity to certain substances entering the body, with the development of clinical signs characteristic of a true allergy. At the same time, there are no immunological reactions that occur with allergies, and the inflammatory process develops due to a violation of histamine metabolism, inadequate activation of complement and other mechanisms. For the development of pseudoallergy, a fairly large amount of the substance that causes intolerance (food, additives or medicines) is required. The diagnosis of pseudoallergy is based on the exclusion of a true allergy. Treatment involves the rejection of problematic products, the use of antihistamines.
T78.4 Allergy, unspecified
Pseudoallergy (false allergy) is the development of a pathological process identical to an allergic reaction in clinical manifestations, but with the absence of an immunological stage (the substance that caused the reaction is not an antigen, there is no production of immunoglobulins). The pseudoallergic reaction begins immediately with the release of inflammatory mediators by the cells. Most often, pseudoallergy occurs on food products, food additives and medicines entering the body. According to statistics, it is pseudoallergic reactions that are the most common, occurring during the life of almost 70% of the population (true allergy is observed much less often – in 1-10% of adults and children).
There are three main factors contributing to the development of pseudoallergic reactions. This is a violation of histamine metabolism, inadequate complement activation and a violation of fatty acid metabolism. Most often, pseudoallergy occurs when histamine metabolism is disrupted due to increased histaminoliberation, reduced histaminopexia, dysbiosis and excessive consumption of histamine-containing products.
Intensive histamine release occurs as a result of exposure to mast cells and basophils of liberating substances: eggs and seafood, chocolate, strawberries, nuts, canned foods, etc. In addition, histamine can be released from cells when exposed to various physical factors: high and low temperature, vibration, ultraviolet radiation; chemical effects of acids and alkalis, medications.
Pseudoallergy often develops in chronic diseases of the gastrointestinal tract, accompanied by a violation of the acidity of gastric juice and damage to the mucous membrane of the stomach and intestines, which leads to easier penetration of liberators to mast cells present in the digestive tract and intense release of histamine and other inflammatory mediators.
Pseudoallergy can occur when the process of histamine inactivation is disrupted (reduced histaminopexy) due to intestinal and liver diseases, dysbiosis, various intoxications, prolonged use of certain medications.
Pseudoallergic reactions quite often develop when eating foods containing an increased amount of histamine, tyramine. Such products include various types of cheese, red wine, semi-finished products subjected to fermentation and canning: canned meat and fish, sausages and ham, sausages, pickled tomatoes and cucumbers, herring, as well as chocolate, spinach, cocoa beans, brewer’s yeast, etc.
Another causal factor causing the development of pseudoallergy is various food additives that are dyes (tartazine and sodium nitrite), preservatives (benzoic acid, sodium glutamate, salicylates), flavors, thickeners, etc. Pseudoallergy can also occur when products contaminated with pesticides, nitrates and nitrites, heavy metals, toxins enter the body microorganisms.
Much less often, pseudoallergy develops due to inadequate complement activation in some immunodeficiency conditions, in particular in hereditary angioedema. Sometimes the appearance of pseudoallergy may be due to the use of some nonsteroidal anti-inflammatory drugs that disrupt the exchange of arachidonic acid.
Symptoms of pseudoallergy
The clinical signs of a false allergy are similar to the symptoms found in allergic diseases. In this case, the pathological process leads to a local or systemic increase in the permeability of peripheral vessels, edema, inflammation, muscle spasm of internal organs, damage to blood cells.
Clinical manifestations of pseudoallergy depend on the predominant lesion of a certain organ and body system. Most often these are rashes on the skin by the type of urticaria, local swelling of the skin in the face and neck (Quincke’s edema). Often there is a violation of the function of the gastrointestinal tract with the appearance of abdominal pain, nausea and vomiting, flatulence, diarrhea, signs of bronchopulmonary damage (shortness of breath, suffocation, cough) and the cardiovascular system (cardiac arrhythmias, swelling on the legs, fainting due to a decrease in blood pressure).
The emerging symptoms of pseudoallergy have their own characteristics depending on the causal factor that caused the development of the pathological process. Thus, a sharp release of histamine by cells leads to a marked increase in its concentration in the blood and the appearance of vegetative-vascular manifestations in the form of skin hyperemia, a feeling of heat throughout the body, migraine headaches, dizziness, difficulty breathing. At the same time, there are often signs of gastrointestinal distress (nausea, decreased appetite, rumbling in the stomach, diarrhea). Disorders of arachidonic acid metabolism in pseudoallergy are manifested by symptoms observed in bronchial asthma (a feeling of lack of air, cough, attacks of suffocation).
With pseudoallergy, anaphylactoid reactions can be observed, similar to anaphylactic shock, but differing from it by the absence of pronounced disorders of the circulatory system, damage mainly to one organ or system, and a favorable outcome of the disease.
The diagnosis of pseudoallergy is based on a thorough analysis of anamnestic information, the identification of symptoms that occur mainly in pseudoallergic reactions and laboratory studies that allow to exclude true allergies.
Distinctive clinical signs of pseudoallergy: development in children older than one year and in adults, the occurrence of a reaction to liberator at first contact and the absence of constant exacerbations during repeated contacts with it, the presence of a clear dependence of the manifestations of pseudoallergy on the amount of incoming product, lack of cross-sensitivity, locality, limitation of the pathological process and its clinical manifestations by one organ (system).
When conducting laboratory studies with pseudoallergy, there is usually no eosinophilia in the blood test, the level of total immunoglobulin E is within normal limits, and the results of determining specific immunoglobulins in the blood and skin allergy tests are negative.
In specialized clinics, such methods as conducting a test with the introduction of histamine into the duodenum 12 (if there is food intolerance), determining the fluorescence of lymphocytes (with urticaria), indomethacin test (with aspirin bronchial asthma), elimination-provocative tests and pr .
Treatment of pseudoallergy
First of all, it is necessary to stop (if possible) the intake of liberating substances into the body that cause the appearance of a pathological pseudoallergic reaction in this patient (stop taking aspirin and other nonsteroidal anti-inflammatory drugs for aspirin asthma, food coloring tartazine – for food intolerance, etc.).
If the development of pseudoallergy is associated with an increased release of histamine by cells, limit the intake of products that stimulate this process and contain histamine in increased amounts, and also recommend oral administration of cromoline-sodium in sufficiently large doses. In the presence of gastrointestinal diseases (gastroduodenitis with increased secretory function, peptic ulcer of the duodenum 12), dietary nutrition using oatmeal porridge, rice broth, as well as taking medications that reduce secretion and have an enveloping effect on the gastric and intestinal mucosa is recommended. In the presence of dysbiosis, its correction is carried out and the amount of carbohydrates in the diet is reduced.
In case of pseudoallergy with clinical manifestations in the form of urticaria (in violation of histamine inactivation), administration of histamine solution in a gradually increasing dose is prescribed. With pseudoallergic hereditary edema, Quincke is injected with a C1 inhibitor or fresh (freshly frozen) plasma, as well as testosterone preparations.
Prevention of pseudoallergy is based on the exclusion of factors that cause its development: refusal to take potential food liberators, certain medications and radiopaque substances, compliance with an elimination diet, timely treatment of concomitant gastrointestinal diseases.