Table causes and symptoms of different types of allergies. Characteristics of the types of allergic reactions

Different types of allergies are observed in almost half of the people living in large cities. The prevalence of this disease among villagers is much less. But this is recorded data based on patients' requests to doctors.

According to medical forecasts, there are many more allergy sufferers in the world - it's just that some allergic reactions are weak, do not cause serious discomfort, so people do not seek medical help.

Clinical picture

WHAT DOCTORS SAY ABOUT EFFECTIVE ALLERGY TREATMENTS

Vice-President of the Association of Children's Allergists and Immunologists of Russia. Pediatrician, allergist-immunologist. Smolkin Yuri Solomonovich

Practical medical experience: more than 30 years

The first descriptions of such a disease are found in the writings of ancient healers of the 5th century BC. Back then, allergies were extremely rare.

In recent decades, the number of patients has been constantly growing. There are several reasons for this: weakened immunity, an increase in the number of toxic substances that are used everywhere, a desire for sterility and a minimal pathogenic load on the immune system.

As a result, he becomes too "suspicious" and sees the enemy in familiar and everyday substances - even those that do not pose a potential danger.

What is an allergy and why does it occur?

This is the individual sensitivity of the human body, more precisely, its immune system to a certain irritant substance. The immune system perceives this substance as a serious threat.

Normally, the immune system "monitors" bacteria, viruses and other pathogens that enter the body in order to neutralize or destroy them in time, preventing the disease.

Allergy is a “false alarm” of the immune system, which is based on an erroneous perception of an allergen substance. Faced with an irritant, he perceives a certain substance as a pathogen, and reacts with the release of histamine. Histamine itself provokes the appearance of signs characteristic of allergies. The nature of the symptoms themselves depends on the type of allergen, the place of its entry and the degree of individual sensitivity.

The cause of allergies is not at all increased vigilance of the immune system, but a malfunction in its work. This failure can be caused by a single factor or a combination of them:

1. Weakening of the immune system, which occurs in the presence of chronic diseases, helminthic invasions.
2. Heredity. If any allergy, even a mild one, is in one parent, this gives a 30% chance that this disease will manifest itself in the baby. If both parents have manifestations of this disease to one degree or another, the likelihood that a child will be born with an allergic person increases to almost 70%.
3. Genetic failure, as a result of which the immune system does not work correctly.
4. Violation of the composition of the intestinal microflora.
5. Formation of immunity in conditions of high purity. Without encountering pathogens, it "trains" on the surrounding substances.
6. Contact with a large amount of "chemistry", as a result of which the body perceives any new substance as a potential threat.

An allergen (a substance to which an atypical reaction develops) can be anything from house dust to food and even medicines.

Most allergens are of a protein nature (they contain protein components or form amino acids when they enter the human body). But some have nothing to do with amino acids: sunlight (one of the common causes of dermatitis), water, low temperatures.

The most common allergens are:

• plant pollen;
• dust and its components;
• fungal spores;
• medicines;
• food products;
• fragments of saliva of domestic animals.

Allergies can be congenital or acquired.

Roza Ismailovna Yagudina, d. farm. n., prof., head. Department of Organization of Drug Supply and Pharmacoeconomics and Head. Laboratory of Pharmacoeconomic Research of the First Moscow State Medical University named after A.I. I. M. -Sechenov.

Evgenia Evgenievna Arinina, Candidate of Medical Sciences, Leading Researcher, Laboratory of Pharmacoeconomic Research, First Moscow State Medical University. I. M. -Sechenov.

About the causes of allergies

Probably, today there is not a single person who has not experienced an allergic reaction at least once in his life. Children are especially susceptible to allergies. The prevalence of various types of allergies is constantly growing, their number and severity are increasing. This is primarily due to environmental pollution and the appearance in everyday life of a large number of chemicals - allergens.

Allergy occupies one of the leading places in terms of prevalence, and the rate of its annual growth suggests the beginning of an epidemic of allergic diseases. Today, the prevalence of allergic rhinitis in developed countries is about 20%, bronchial asthma - about 8% (more than half of them - atopic form of bronchial asthma), drug allergy - more than 25% of inpatients. In this regard, almost every day a large number of doctors of various specialties are faced with various types of allergies: atopic dermatitis, food and drug allergies, etc.

Allergy is a hypersensitivity reaction mediated by immunological mechanisms. In most patients, the development of an allergic reaction, as a rule, is associated with IgE-class antibodies, and therefore such allergic reactions are also called "IgE-mediated -allergy".

The widespread and uncontrolled use of drugs can also cause the development of allergies. In the occurrence of allergic diseases, climatic factors, heredity, somatic pathology, as well as the nature of nutrition play an important role. Various substances trigger an allergic reaction, which, when entering the body, cause an immune response of a humoral or cellular type.

According to the State Research Center "Institute of Immunology of the Federal Medical and Biological Agency of Russia", 65% of patients in the institute's hospital indicated food intolerance. Of these, true allergic reactions to food allergens were detected in almost 35%, and pseudo-allergic reactions in 65% of patients. At the same time, true food allergy, as the main allergic disease, has accounted for about 5.5% in the structure of all allergic pathology over the past 5 years, and reactions to impurities in the composition of food products - 0.9%.

Allergic diseases in persons with an atopic constitution can be called atopic (atopic rhinitis, atopic bronchial asthma, etc.). However, it should be noted that atopic allergic reactions develop only if there is a genetic predisposition of the body to develop IgE-mediated sensitization to the most common environmental products, upon contact with which most people do not develop sensitization (plant pollen, excretions of domestic animals, mites, house dust and etc.). The disease is not classified as atopic if the patient has positive skin tests or specific IgE antibodies to allergens that patients do not encounter so often in everyday life, and if the doses of allergens are higher than those in atopic diseases, and their penetration into the body does not occur through the mucous membranes (but through the sting of a wasp or bee, for example). Does not apply to atopic reactions and drug allergy.

Types of allergic reactions

There are allergic reactions of immediate, delayed and mixed type. In the pathogenesis of allergic reactions of the immediate type, the following stages are distinguished:

Immunological stage- sensitization of the body as a result of contact with the allergen - the formation of antibodies (AT) that can interact with the allergen. If by the time the AT is formed, the allergen has already been removed from the body, then clinical manifestations do not occur. With repeated exposure to an allergen in an organism already sensitized to it, an allergen-AT complex is formed.

pathochemical stage- the release of biologically active substances (BAS), allergy mediators: histamine, serotonin, bradykinin, acetylcholine, heparin, etc. This process occurs as a result of allergic alteration by the antigen-antibody complex of tissues rich in mast cells (skin vessels, serous membranes, loose connective tissue, etc.). There is an inhibition of the mechanisms of their inactivation, the histamino- and serotonin-pectic properties of the blood decrease, the activity of histaminase, cholesterase, etc. decreases.

Pathophysiological stage- result of exposure to mediators of allergy on tissues. The stage is characterized by a disorder of hematopoiesis, spasm of the smooth muscles of the bronchi, intestines, a change in the composition of the blood serum, a violation of its coagulability, cell cytolysis, etc.

Types of allergic reactions:

1. Type I allergic reaction, or immediate type reaction (anaphylactic, atopic type). It develops with the formation of antibodies belonging to the class IgE and lgG4, which are fixed on mast cells and basophilic leukocytes. When these antibodies are combined with an allergen, mediators are released: histamine, heparin, serotonin, platelet-activating factor, prostaglandins, leukotrienes, etc., which determine the clinic of an immediate type allergic reaction that occurs after 15-20 minutes.
2. An allergic reaction of type II, or a reaction of the cytotoxic type, is characterized by the formation of AT related to IgG and IgM. This type of reaction is caused only by antibodies, without the participation of mediators, immune complexes and sensitized lymphocytes. Antibodies activate complement, which causes damage and destruction of body cells, followed by phagocytosis and their removal. It is by the cytotoxic type that drug-allergy develops.
3. Allergic type III reaction, or reaction of the immunocomplex type (Arthus type), occurs as a result of the formation of circulating immune complexes, which include IgG and IgM. This is the leading type of reaction in the development of serum sickness, allergic alveolitis, drug and food allergies, in a number of autoallergic diseases (SLE, rheumatoid arthritis, etc.).
4. Type IV allergic reaction, or delayed-type allergic reaction (delayed-type hypersensitivity), in which the role of antibodies is performed by sensitized T-lymphocytes that have specific receptors on their membranes that can interact with sensitizing antigens. When a lymphocyte is combined with an allergen, mediators of cellular immunity - lymphokines - are released, causing the accumulation of macrophages and other lymphocytes, resulting in inflammation. Delayed-type reactions develop in a sensitized organism 24-48 hours after contact with the allergen. The cellular type of reaction underlies the development of viral and bacterial infections (tuberculosis, syphilis, leprosy, brucellosis, tularemia), some forms of infectious-allergic bronchial asthma, rhinitis, transplantation and antitumor immunity.

In the diagnosis of allergic reactions, it is important to identify the allergen, its causal relationship with clinical manifestations, and the type of immunological reaction. The generally accepted classification of diseases depending on the type of reaction:

1. Immediate-type hypersensitization reaction:

• anaphylactic shock
• angioedema angioedema
• hives

2. Delayed-type hypersensitization reaction:

• fixed (limited, local) drug-induced stomatitis
• common toxic-allergic stomatitis (catarrhal, catarrhal-hemorrhagic, erosive-ulcerative, ulcerative-necrotic stomatitis, cheilitis, glossitis, gingivitis)

3. Systemic toxic-allergic diseases:

• Lyell's disease
• erythema multiforme exudative
• Stevens-Johnson syndrome
• chronic recurrent aphthous stomatitis
• Behçet's syndrome
• Sjögren's syndrome

Table 1 presents the clinical manifestations of various variants of allergic reactions.

However, in recent years, the so-called "contact" forms of allergic reactions have become more and more widespread, namely:

Atopic dermatitis, manifested by dryness, increased skin irritation and severe itching. It proceeds with periods of exacerbations and remissions. The acute stage is manifested by erythema, papules, peeling and swelling of the skin, the formation of areas of erosion, weeping and crusts. Accession of a secondary infection leads to the development of pustular lesions.

The chronic stage of atopic dermatitis is characterized by thickening of the skin (lichenization), the severity of the skin pattern, cracks on the soles and palms, scratching, increased pigmentation of the skin of the eyelids. In the chronic stage, symptoms typical of atopic dermatitis develop: multiple deep wrinkles on the lower eyelids, weakening and thinning of hair at the back of the head, shiny nails with sharpened edges due to constant scratching of the skin (which leads to its secondary infection), puffiness and hyperemia of the soles, cracks , - peeling.

Bronchial asthma(atopic form) and allergic rhinitis, diseases associated with IgE-mediated reactions. The clinic of these conditions is well known. Such reactions develop, as a rule, when air containing α-allergens is inhaled.

Gainer syndrome, occurs in children in the first months of life and is characterized by a non-IgE-mediated immune response to cow's milk proteins. Clinically, this is manifested by wheezing, shortness of breath, cough, recurrent infiltrates in the lungs, pulmonary hemosiderosis, anemia, recurrent pneumonia, growth retardation. Rhinitis, cor pulmonale formation, recurrent otitis media, as well as various symptoms of a lesion of the gastrointestinal tract are possible.

To non-IgE-mediated allergy include serum sickness associated with the production of certain IgG isotypes, as well as allergic alveolitis, which develops with chronic inhalation of dust containing high concentrations of antigens of certain fungi (“farmer’s lung”) and bird droppings proteins (“pigeon breeder’s lung”).

Such a variety of clinical manifestations indicates how important a correctly formulated α-diagnosis is for the selection of effective pharmacotherapy.

Table 1. Clinical manifestations of various types of allergic reactions

Pharmacotherapy of allergic reactions

Consider two main groups of drugs used to treat allergic reactions:

1. Drugs that block histamine receptors (H1 receptors), 1st generation: chloropyramine, clemastine, hifenadine; 2nd (new) generation: cetirizine, ebastine, loratadine, fexofenadine, desloratadine, -levocetirizine.
2. For prophylactic purposes, drugs are prescribed that increase the ability of blood serum to bind histamine (now they are used less frequently) and inhibit the release of histamine from mast cells,  -ketotifen, cromoglycic acid preparations. This group of drugs is prescribed for prophylactic purposes for a long time, at least 2-4 months.

Steroids, which are also used in allergic diseases, will be the subject of a separate article.

1st generation antihistamines-competitive blockers of H1 receptors, so their binding to the receptor is rapidly reversible. In this regard, to obtain a clinical effect, it is necessary to use these drugs in high doses with a frequency of up to 3-4 times a day, however, they can be used in combination with 2nd generation drugs when administered at night. The main side effects of H1 antagonists of the 1st generation: penetration through the blood-brain barrier; blockade of both H1 receptors and M-cholinergic receptors, 5HT receptors, D receptors; local irritating action; analgesic effect; disorders of the gastrointestinal tract (nausea, abdominal pain, loss of appetite). However, the most well-known side effect of 1st generation antihistamines is sedation. The sedative effect may vary from mild drowsiness to deep sleep.

The following 1st generation drugs are most widely used in clinical practice: ethanolamines, ethylenediamines, piperidines, alkylamines, phenothiazines. Ethanolamines include: diphenhydroline, -clemastine.

Diphenhydramine- one of the main representatives of 1st generation antihistamines. It penetrates the blood-brain barrier, has a pronounced sedative effect, moderate antiemetic properties.

Table 2. INN and trade names of drugs used in allergic reactions

clemastine in terms of pharmacological properties, it is close to diphenhydramine, but has a more pronounced antihistamine activity, a longer action (for 8-12 hours) and a moderate sedative effect.

Classic representative ethylenediamines is chloropyramine. This is one of the representatives of the 1st generation, which can be combined with a 2nd generation antihistamine.

Among piperidine derivatives, cyproheptadine is most widely used, which belongs to antihistamines with pronounced antiserotonin activity. In addition, cyproheptadine has the ability to stimulate appetite, as well as block growth hormone hypersecretion in acromegaly and ACTH secretion in Itsenko-Cushing syndrome.

Representative alkylamines used to treat allergies is dimethindene. The drug acts during the day, has a pronounced sedative effect, like other drugs of the 1st generation, the development of tachyphylaxis is noted. Side effects are also manifested by dryness of the mucous membranes of the mouth, nose, throat. In particularly sensitive patients, urination disorders and blurred vision may occur. Other manifestations of the action on the central nervous system may be coordination disorders, dizziness, a feeling of lethargy, a decrease in the ability to coordinate attention.

Hifenadine has a low lipophilicity, poorly penetrates the blood-brain barrier, activates diamine oxidase (histaminase), which destroys histamine. Due to the fact that the drug does not penetrate well through the blood-brain barrier, after taking it, either a weak sedative effect or its absence is noted. Approved for use in young children.

H1 antagonists of the 2nd(new) generations are distinguished by a high selective ability to block peripheral H1 receptors. They belong to different chemical groups. Most H1-antagonists of the 2nd generation bind to H1-receptors non-competitively and are prodrugs, exerting an antihistamine effect due to the accumulation of pharmacologically active metabolites in the blood. In this regard, metabolized drugs show their antihistamine effect to the maximum after the appearance in the blood of a sufficient concentration of active metabolites. Such compounds can hardly be displaced from the receptor, and the resulting ligand-receptor complex dissociates relatively slowly, which explains the longer action of such drugs. H1 antagonists of the 2nd generation are easily absorbed into the blood.

The main advantages of H1 antagonists of the 2nd generation: high specificity and high affinity for H1 receptors; rapid onset of action; long-term action (up to 24 hours); lack of blockade of receptors of other mediators; obstruction through the blood-brain barrier; lack of connection of absorption with food intake; absence of -tachyphylaxis.

Among the modern antihistamines of the new generation, the following groups are used in clinical practice: piperazine, azatidine, piperidine derivatives, α-hydroxypiperidines.

Piperazine derivatives-cetirizine, a selective H1 receptor blocker, does not have a significant sedative effect and, like other representatives of the 2nd generation, does not have an antiserotonin, anticholinergic effect, does not enhance the effect of -alcohol.

Azatidine derivatives— loratadine, refers to metabolized H1-antagonists, is a selective blocker of H1-receptors, has no antiserotonin, anticholinergic action, does not enhance the effect of alcohol. Desloratadine is a pharmacologically active metabolite of loratadine, has a high affinity for H1 receptors and can be used at a lower therapeutic dose than loratadine (5 mg per day).

Oxypiperidines - ebastine, a highly selective non-sedating H1 antagonist of the 2nd generation. Refers to metabolizable drugs. The pharmacologically active metabolite is karebastin. Ebastine has a pronounced clinical effect in both seasonal and year-round allergic rhinitis caused by sensitization to pollen, household and food allergens. The anti-allergic effect of ebastine begins within an hour after oral administration and lasts up to 48 hours. Ebastine is prescribed for children from the age of 6.

Piperidines - fexofenadine, the final pharmacologically active metabolite of terfenadine, has all the advantages of H1-antagonists of the 2nd generation.

Drugs that inhibit the release of mediators from mast cells and other target cells of allergy.

Ketotifen- has an anti-allergic effect due to inhibition of the secretion of allergy mediators from mast cells and blockade of H1-receptors -histamine.

Drugs that increase the ability of blood serum to bind histamine, — hystaglobulin, a combined preparation consisting of normal human immunoglobulin and histamine hydrochloride. With the introduction of the drug into the body, antihistamine antibodies are produced and the ability of the serum to inactivate free histamine increases. Used in the treatment of urticaria, Quincke's edema, neurodermatitis, eczema, bronchial asthma.

Cromoglycic acid preparations(sodium cromoglycate). Sodium cromoglycate acts by a receptor mechanism, does not penetrate into cells, is not metabolized and is excreted unchanged in the urine and bile. These properties of sodium cromoglycate may explain the extremely low incidence of unwanted side effects. In food allergies, the oral dosage form of cromoglycic acid - nalcrom is of particular importance.

Thus, the choice of antihistamines in the treatment of allergies requires the doctor to take into account the individual characteristics of the patient, the characteristics of the clinical course of the allergic disease, the presence of concomitant diseases, the safety profile of the recommended medication. Of considerable importance is the availability of the drug for the patient.

When prescribing antihistamines, especially for children and the elderly, one should strictly adhere to the recommendations set forth in the instructions for use.

Among modern antihistamines, there are drugs that have a high degree of safety, which allows pharmacies to dispense them without a doctor's prescription. However, patients should be advised to consult their physician as to which of the drugs is most indicated in each particular case.

An allergic reaction is a pathological variant of the interaction of the immune system with a foreign agent (allergen), the consequence of which is damage to body tissues.

Immune system: structure and functions

The structure of the immune system is very complex, it includes individual organs (thymus gland, spleen), islets of lymphoid tissue scattered throughout the body (lymph nodes, pharyngeal lymphoid ring, intestinal nodes, etc.), blood cells (various types of lymphocytes) and antibodies (special protein molecules).

Some links of immunity are responsible for the recognition of foreign structures (antigens), others have the ability to remember their structure, and others provide the production of antibodies to neutralize them.

Under normal (physiological) conditions, an antigen (for example, the smallpox virus), when it enters the body for the first time, causes an immune system reaction - it is recognized, its structure is analyzed and remembered by memory cells, and antibodies are produced to it that remain in the blood plasma. The next intake of the same antigen leads to an immediate attack of pre-synthesized antibodies and its rapid neutralization - thus, the disease does not occur.

In addition to antibodies, cellular structures (T-lymphocytes) are also involved in the immune response, capable of releasing enzymes that destroy the antigen.

Allergy: causes

An allergic reaction has no fundamental differences from the normal response of the immune system to an antigen. The difference between the norm and pathology lies in the inadequacy of the ratio of the strength of the reaction and the cause that causes it.

The human body is constantly exposed to various substances that enter it with food, water, inhaled air, through the skin. In the normal state, most of these substances are "ignored" by the immune system, there is a so-called refractoriness to them.

Allergy is an abnormal sensitivity to substances or physical factors, to which an immune response begins to form. What is the reason for the breakdown of the protective mechanism? Why does one person develop a severe allergic reaction to something that the other simply does not notice?

An unequivocal answer to the question about the causes of allergies has not been received. The dramatic increase in the number of sensitized people in recent decades can partly be explained by the sheer number of new compounds they encounter in their daily lives. These are synthetic fabrics, perfumes, dyes, drugs, food additives, preservatives, etc. The combination of antigenic overload of the immune system with innate structural features of some tissues, as well as stress and infectious diseases, can cause a malfunction in the regulation of protective reactions and the development of allergies.

All of the above applies to external allergens (exoallergens). In addition to them, there are allergens of internal origin (endoallergens). Some structures of the body (for example, the lens of the eye) do not come into contact with the immune system - this is required for their normal functioning. But with certain pathological processes (injuries or infections), such natural physiological isolation is violated. The immune system, having detected a previously inaccessible structure, perceives it as foreign and begins to react by forming antibodies.

Another option for the occurrence of internal allergens is a change in the normal structure of any tissue under the influence of burns, frostbite, radiation or infection. The altered structure becomes "alien" and causes an immune response.

Mechanism of an allergic reaction

All types of allergic reactions are based on a single mechanism in which several stages can be distinguished.

1. Immunological stage. The first meeting of the body with the antigen and the production of antibodies to it occurs - sensitization occurs. Often, by the time antibodies are formed, which takes some time, the antigen has time to leave the body, and the reaction does not occur. It happens with repeated and all subsequent receipts of the antigen. Antibodies attack the antigen to destroy it and form antigen-antibody complexes.
2. pathochemical stage. The resulting immune complexes damage special mast cells found in many tissues. These cells contain granules containing inflammatory mediators in an inactive form - histamine, bradykinin, serotonin, etc. These substances become active and are released into the general circulation.
3. Pathophysiological stage occurs as a result of the action of inflammatory mediators on organs and tissues. There are various external manifestations of allergies - spasm of the muscles of the bronchi, increased intestinal motility, gastric secretion and mucus formation, capillary dilation, the appearance of a skin rash, etc.

Classification of allergic reactions

Despite the common mechanism of occurrence, allergic reactions have clear differences in clinical manifestations. The existing classification distinguishes the following types of allergic reactions:

I type - anaphylactic , or allergic reactions of immediate type. This type arises due to the interaction of antibodies of group E (IgE) and G (IgG) with the antigen and the sedimentation of the formed complexes on the membranes of mast cells. This releases a large amount of histamine, which has a pronounced physiological effect. The time of occurrence of the reaction is from several minutes to several hours after the penetration of the antigen into the body. This type includes anaphylactic shock, urticaria, atopic bronchial asthma, allergic rhinitis, Quincke's edema, many allergic reactions in children (for example, food allergies).

II type - cytotoxic (or cytolytic) reactions. In this case, immunoglobulins of groups M and G attack antigens that are part of the membranes of the body's own cells, resulting in cell destruction and death (cytolysis). The reactions are slower than the previous ones, the full development of the clinical picture occurs after a few hours. Type II reactions include hemolytic anemia and hemolytic jaundice of newborns with Rhesus conflict (in these conditions, massive destruction of red blood cells occurs), thrombocytopenia (platelets die). This also includes complications during blood transfusion (blood transfusion), the administration of drugs (toxic-allergic reaction).

III type - immunocomplex reactions (Arthus phenomenon). A large number of immune complexes, consisting of antigen molecules and antibodies of groups G and M, are deposited on the inner walls of the capillaries and cause their damage. Reactions develop within hours or days after the interaction of the immune system with the antigen. This type of reaction includes pathological processes in allergic conjunctivitis, serum sickness (immune response to serum administration), glomerulonephritis, systemic lupus erythematosus, rheumatoid arthritis, allergic dermatitis, hemorrhagic vasculitis.

IV type - late hypersensitivity , or delayed-type allergic reactions that develop a day or more after the antigen enters the body. This type of reaction occurs with the participation of T-lymphocytes (hence another name for them - cell-mediated). The attack on the antigen is not provided by antibodies, but by specific clones of T-lymphocytes that have multiplied after previous antigen intakes. Lymphocytes secrete active substances - lymphokines that can cause inflammatory reactions. Examples of diseases based on type IV reactions are contact dermatitis, bronchial asthma, and rhinitis.

V type - stimulating reactions hypersensitivity. This type of reaction differs from all previous ones in that antibodies interact with cellular receptors designed for hormone molecules. Thus, antibodies “replace” a hormone with its regulatory action. Depending on the specific receptor, the result of the contact of antibodies and receptors in type V reactions may be stimulation or inhibition of organ function.

An example of a disease that occurs on the basis of the stimulating effect of antibodies is diffuse toxic goiter. In this case, antibodies irritate the receptors of thyroid cells intended for thyroid-stimulating hormone of the pituitary gland. The consequence is an increase in the production of thyroxine and triiodothyronine by the thyroid gland, the excess of which causes a picture of toxic goiter (Basedow's disease).

Another variant of type V reactions is the production of antibodies not to receptors, but to the hormones themselves. In this case, the normal concentration of the hormone in the blood is insufficient, since part of it is neutralized by antibodies. Thus, insulin-resistant diabetes occurs (due to insulin inactivation by antibodies), some types of gastritis, anemia, and myasthenia gravis.

Types I-III combine acute allergic reactions of the immediate type, the rest are of the delayed type.

Allergy general and local

In addition to the division into types (depending on the rate of occurrence of manifestations and pathological mechanisms), allergies are divided into general and local.

With a local variant, the signs of an allergic reaction are local (limited) in nature. This variety includes the Arthus phenomenon, skin allergic reactions (the Overy phenomenon, the Praustnitz-Küstner reaction, etc.).

Most of the immediate reactions are classified as general allergies.

Pseudoallergy

Sometimes there are conditions that are clinically practically indistinguishable from the manifestations of allergies, but in fact they are not. With pseudo-allergic reactions, there is no main mechanism of allergy - the interaction of an antigen with an antibody.

Pseudo-allergic reaction (the obsolete name "idiosyncrasy") occurs when food, drugs and other substances enter the body, which, without the participation of the immune system, cause the release of histamine and other inflammatory mediators. The consequence of the action of the latter is manifestations that are very similar to the "standard" allergic reaction.

The cause of such conditions may be a decrease in the neutralizing function of the liver (with hepatitis, cirrhosis, malaria).

Therapy of any diseases of an allergic nature should be dealt with by a specialist - an allergist. Attempts at self-treatment are ineffective and can lead to the development of severe complications.

The attention of the mass reader is offered a book on one of the most pressing problems of our time - allergies. Perhaps there is not a single person who has not heard this strange word. And what does it mean? Is this a disease or a normal manifestation of the body? Why and who gets allergies? Can it be cured? How to live on for a person who has an allergy? All these questions and many more are answered by the author of this book. The reader will learn about the causes of the development and exacerbation of allergies, a variety of methods of treatment and prevention of this condition.

Types of allergic reactions

Depending on the time of occurrence, all allergic reactions can be divided into 2 large groups: if allergic reactions between the allergen and body tissues occur immediately, then they are called immediate-type reactions, and if after a few hours or even days, then these are delayed-type allergic reactions. According to the mechanism of occurrence, 4 main types of allergic reactions are distinguished.

Type I allergic reactions

The first type includes allergic reactions (hypersensitivity) of the immediate type. They are called atopic. Allergic reactions of immediate type are the most common immunological diseases. They affect approximately 15% of the population. Patients with these disorders have abnormal immune responses called atopic. Atopic disorders include bronchial asthma, allergic rhinitis and conjunctivitis, atopic dermatitis, allergic urticaria, angioedema, anaphylactic shock, and some cases of allergic lesions of the gastrointestinal tract. The mechanism of development of the atopic state is not fully understood. Numerous attempts by scientists to find out the causes of its occurrence have revealed a number of characteristics that distinguish some individuals with atopic conditions from the rest of the population. The most characteristic feature of such people is an impaired immune response. As a result of the impact of the allergen on the body, which occurs through the mucous membranes, an unusually high amount of specific allergic antibodies is synthesized - reagins, immunoglobulins E. People with allergies have a reduced content of another important group of antibodies - immunoglobulins A, which are "defenders" of the mucous membranes. Their deficiency opens access to the surface of the mucous membranes to a large number of antigens, which ultimately provokes the development of allergic reactions.

In such patients, along with atopy, the presence of dysfunction of the autonomic nervous system is also noted. This is especially true for people suffering from bronchial asthma and atopic dermatitis. There is an increased permeability of the mucous membranes. As a result of the fixation of so-called reagins on cells with biologically active substances, the process of damage to these cells increases, as well as the release of biologically active substances into the bloodstream. In turn, biologically active substances (BAS) with the help of special chemical mechanisms damage already specific organs and tissues. The so-called "shock" organs in the reaginic type of interaction are primarily the respiratory organs, intestines, and conjunctiva of the eyes. BAS reagin reactions are histamine, serotonin and a number of other substances.

In the reaginic type of allergy, there is a sharp increase in the permeability of the microvasculature. In this case, the fluid leaves the vessels, resulting in the development of edema and inflammation, local or widespread. The amount of discharge of mucous membranes increases, bronchospasm develops. All this is reflected in clinical symptoms.

Thus, the development of immediate type hypersensitivity begins with the synthesis of immunoglobulins E (proteins with antibody activity). The stimulus for the production of reaginic antibodies is exposure to the allergen through the mucous membrane. Immunoglobulin E, synthesized in response to immunization through the mucous membranes, is rapidly fixed on the surface of mast cells and basophils, located mainly in the mucous membranes. With repeated exposure to the antigen, immunoglobulin E fixed on the surfaces of mast cells is combined with the antigen. The result of this process is the destruction of mast cells and basophils and the release of biologically active substances, which, damaging tissues and organs, cause inflammation.

Type II allergic reactions

The second type of allergic reactions is called cytotoxic immune reactions. This type of allergy is characterized by the combination of allergen with cells first, and then antibodies with the allergen-cell system. With this triple connection, cell damage occurs. However, another component is involved in this process - the so-called complement system. Other antibodies are already involved in these reactions - immunoglobulins G, M, immunoglobulins E. The mechanism of damage to organs and tissues is not due to the release of biologically active substances, but due to the damaging effect of the above-named complement. This type of reaction is called cytotoxic. The “allergen-cell” complex can be either circulating in the body or “fixed”. Allergic diseases that have a second type of reaction are the so-called hemolytic anemia, immune thrombocytopenia, pulmonary-renal hereditary syndrome (Goodpasture's syndrome), pemphigus, and various other types of drug allergies.

III type of allergic reactions

The third type of allergic reactions is immunocomplex, it is also called "immune complex disease". Their main difference is that the antigen is not bound to the cell, but circulates in the blood in a free state, without being attached to tissue components. In the same place, it combines with antibodies, more often of classes G and M, forming antigen-antibody complexes. These complexes, with the participation of the complement system, are deposited on the cells of organs and tissues, damaging them. Inflammatory mediators are released from damaged cells and cause intravascular allergic inflammation with changes in surrounding tissues. The above complexes are most often deposited in the kidneys, joints and skin. Examples of diseases caused by reactions of the third type are diffuse glomerulonephritis, systemic lupus erythematosus, serum sickness, essential mixed cryoglobulinemia and prehepatogenic syndrome, which manifests itself with signs of arthritis and urticaria and develops when infected with the hepatitis B virus. Increased vascular permeability plays a huge role in the development of immune complex diseases , which may be exacerbated by the development of an immediate hypersensitivity reaction. This reaction usually proceeds with the release of mast cell contents and basophils.

IV type of allergic reactions

Antibodies do not participate in reactions of the fourth type. They develop as a result of the interaction of lymphocytes and antigens. These reactions are called delayed reactions. Their development occurs 24-48 hours after the allergen enters the body. In these reactions, the role of antibodies is taken by lymphocytes sensitized by the intake of the allergen. Due to the special properties of their membranes, these lymphocytes bind to allergens. In this case, mediators, the so-called lymphokines, are formed and released, which have a damaging effect. Lymphocytes and other cells of the immune system accumulate around the place of entry of the allergen. Then comes necrosis (tissue necrosis under the influence of circulatory disorders) and the replacement development of connective tissue. This type of reaction underlies the development of some infectious-allergic diseases, such as contact dermatitis, neurodermatitis, and some forms of encephalitis. It plays a huge role in the development of such diseases as tuberculosis, leprosy, syphilis, in the development of transplant rejection, in the occurrence of tumors. Often, patients can combine several types of allergic reactions at once. Some scientists distinguish the fifth type of allergic reactions - mixed. So, for example, with serum sickness, allergic reactions of the first (reaginic), second (cytotoxic), and third (immunocomplex) types can develop.

As our knowledge of the immune mechanisms of tissue damage development increases, the boundaries between them (from the first to the fifth type) become more and more vague. In fact, most diseases are caused by the activation of different types of inflammatory responses that are interrelated.

Stages of allergic reactions

All allergic reactions in their development go through certain stages. As you know, getting into the body, the allergen causes sensitization, i.e. immunologically increased sensitivity to the allergen. The concept of allergy includes not only an increase in sensitivity to any allergen, but also the realization of this increased sensitivity in the form of an allergic reaction.

Initially, sensitivity to the antigen increases, and only then, if the antigen remains in the body or enters it again, does an allergic reaction develop. This process can be divided in time into two parts. The first part is preparation, increasing the body's sensitivity to an antigen, or, in other words, sensitization. The second part is the possibility of realizing this condition in the form of an allergic reaction.

Academician A.D. Ado singled out stage 3 in the development of allergic reactions of the immediate type.

I. Immunological stage. It covers all changes in the immune system that occur from the moment the allergen enters the body: the formation of antibodies and (or) sensitized lymphocytes and their combination with the allergen that has re-entered the body.

II. The pathochemical stage, or the stage of the formation of mediators. Its essence lies in the formation of biologically active substances. The stimulus for their occurrence is the combination of the allergen with antibodies or sensitized lymphocytes at the end of the immunological stage.

III. Pathophysiological stage, or stage of clinical manifestations. It is characterized by the pathogenic action of the formed mediators on the cells, organs and tissues of the body. Each of the biologically active substances has the ability to cause a number of changes in the body: dilate capillaries, lower blood pressure, cause spasm of smooth muscles (for example, bronchi), disrupt capillary permeability. As a result, a violation of the activity of the organ in which the incoming allergen met with the antibody develops. This phase is visible to both the patient and the doctor, because the clinical picture of an allergic disease develops. It depends on which way and to which organ the allergen entered and where the allergic reaction occurred, on what the allergen was, and also on its quantity.

The hypersensitivity reaction of the body can proceed according to different scenarios. There are four types of allergic reactions in total.

In fact

After a substance of an antigenic nature enters the body, the immune system develops a response in the form of the formation of antibodies, the formation of immune complexes, or the reaction of sensitized lymphocytes. That is, developing allergic reaction. At the beginning of the last century, the American physician Robert Cook proposed to divide all allergic reactions into two types - immediate and delayed. However, this division was incomplete, and in 1969 the immunologists Coombs and Jell proposed a new classification, according to which four main types of allergic reactions are distinguished. Although in some literature there is also a fifth.

It should be noted that with the development of the pathological process, almost all types of reactions of the immunocompetent system are involved, which creates some difficulties in determining the leading type.

I type of reactions

The first type of allergic reactions, as a rule, develops in the first few minutes (or hours) after contact with the allergen. This is an allergic reaction of the anaphylactic type, caused by the interaction of the antigen with reagin or specific antibodies on the surface of the mast cell (immune cells of the connective tissue). Such interactions lead to the release of large amounts of histamine and a number of other vasoactive substances that dilate the vessels, increase the permeability of the vascular wall and increase the contractile activity of smooth muscles (which can cause smooth muscle spasms).

In the vast majority of cases, allergic reactions of the first type occur with the participation of immunoglobulins E, in rare cases - immunoglobulins G.

Typical examples of an allergic reaction of the first type are urticaria, atopic bronchial asthma, vasomotor rhinitis, false croup. In allergic bronchial asthma, as a result of antigen-antibody interaction, spasms of the smooth muscles of the bronchioles occur, which is accompanied by swelling of the mucous membrane and secretion of a large amount of mucus.

II type of reactions

The second type of allergic reaction, also called cytotoxic or cytolytic, occurs with the participation of immunoglobulins G and M. The reaction of the second type, as a rule, proceeds more slowly than the first, and usually begins more than 6 hours after contact with the allergen. The reaction of the second type is characterized by the interaction of circulating antibodies with antigens of a person's own cells. In this case, the death of the cell or a significant decrease in its basic functions occurs.

This type of allergic reaction is typical for drug allergies. , hemolytic anemia, thrombocytopenia and with Rhesus conflict.

ІІІ type of reactions

This type of allergic reaction is known as the Arthus phenomenon or immune complex reaction. This type of reaction develops, as a rule, after 6-12 hours (or several days) after the patient's contact with the allergen. In this case, precipitating immune complexes with an excess of antigens are formed, which are subsequently deposited on the walls of blood vessels, and thereby provoke the development of inflammatory processes.

The third type of allergic reactions develops with allergic conjunctivitis, systemic lupus erythematosus, immunocomplex glomerulonephritis, serum sickness, rheumatoid arthritis and allergic dermatitis.

As in the second type of reactions, in this case the process also proceeds with the participation of immunoglobulins G and M.

Questions from readers

Good day! I've been sick with bronchitis for 3 weeks now October 18, 2013, 17:25 Good day! I've been sick with bronchitis for 3 weeks now. In me, for the second time, the gut is alive, to sleep out at once with me in my bed. Even the fathers have a whale, which one we have more fate. Were already at the Institute of Pulmonology, everything is fine with the lungs, the result for asthma is negative (the two were reconsidered). For three weeks I have had a persistent cough and see a lot of drooling. During the day it’s nothing, but at night there are seizures - I throw up sharply and I can’t breathe again, until I cough up all the saliva (it won’t accumulate and won’t let you breathe). The attack here is 1-2 minutes, I can’t breathe in, until I cough. The nose is not congested. The therapist and pulmonologist heard, they said that such a thing could not happen to bronchitis, wanting to hear wheezing. How can you blame an allergy to a cat in 1.5 years, how is it alive in me, as there were no earlier manifestations? What can cause allergy against the background of bronchitis?

IV type of reactions

The fourth type of allergic reactions is a variant of late hypersensitization, which develops 24-72 hours after the patient has come into contact with the allergen. This type of reaction is due to the interaction of the antigen and the T-lymphocyte sensitive to it. In the case of repeated such contact, specific delayed-type inflammatory reactions develop. For example, it can be allergic dermatitis, or such a reaction can be observed with transplant rejection.

Most often, with the fourth type of allergic reactions, the skin is damaged. , respiratory organs and the gastrointestinal tract, although absolutely all organs and tissues can be involved in the process.