Allergic diseases are a group of diseases caused by an individual’s hypersensitivity to certain foreign substances – allergens and occurring with the development of an IgE-mediated reaction of the immune system. The necessary conditions for the occurrence of allergies are high specificity (reaction strictly to certain antigens), sensitization (hypersensitivity to this allergen) and repeated exposure of the allergen to the body.
The term “allergy”, meaning “response, reaction to someone else” in Greek, was proposed by the Austrian pediatrician K. von Pirke in 1906. Over the past century, allergic diseases have acquired epidemic proportions, and the prevalence of allergies among adults and children continues to increase steadily. According to research, 35% of residents suffer from various allergic diseases in Western countries, in USA – from 17.5% to 30% of the population. These circumstances led to the allocation of a special medical discipline – allergology, which deals with the study of diseases associated with hypersensitivity reactions. The most common allergic diseases include allergic rhinitis, bronchial asthma, urticaria, atopic dermatitis.
The ethological classification of allergic diseases is based on the isolation of a causally significant allergen; within it, food, household, insect, medicinal, and infectious allergies are differentiated. According to the method of penetration into the body, aeroallergens, contact, oral, injectable allergens are distinguished. Taking into account the conditions in which an allergic reaction has developed, domestic, professional, seasonal allergies are distinguished. Depending on the predominant lesion of a particular organ system, the following groups of allergic diseases are distinguished: allergodermatoses (atopic dermatitis, eczema, urticaria, etc.), intestinal allergoses (allergic enterocolitis), respiratory (allergic rhinitis, allergic tracheobronchitis, bronchial asthma), acute allergic reactions (Quincke’s edema, anaphylactic shock).
The symptoms of various allergic diseases are caused by common pathogenetic mechanisms: the release of mast cell mediators and basophils into the tissues or into the blood, which cause characteristic vascular and smooth muscle reactions: edema, hyperemia, itching, hypotension, difficulty breathing.
In this case, the specific form of allergy depends on which organ or tissue the allergen comes into contact with immunoglobulin E, fixed on the cell surface. If this happens in the respiratory tract, a clinic of allergic rhinitis or bronchial asthma may develop, allergic conjunctivitis in the conjunctiva of the eye, urticaria in the surface layers of the dermis, Quincke’s edema in the subcutaneous tissue, etc. Since allergic diseases have extremely diverse manifestations, allergists work closely with dermatologists, pulmonologists, otolaryngologists, gastroenterologists, ophthalmologists, nutritionists and doctors other specialties.
The specific diagnosis of allergic diseases consists in collecting an allergological history, conducting allergy testing (allergy tests and provocative tests), determining general and allergen-specific IgE, if necessary, performing functional studies (spirometry with samples, peak flowmetry). After identifying the causal allergen, it is necessary to take immediate measures to eliminate it, i.e. completely exclude contact with the substance that provokes an allergic disease.
To this end, it may be necessary to change eating habits, abandon the use of certain cosmetics, get rid of upholstered furniture and carpets in the house, stop taking certain medications, change the scope of professional activity, etc. Modern principles of treatment of allergic diseases provide for specific hyposensitization (ASIT) by introducing allergens into the body in gradually increasing doses. After a full course of ASIT, persistent remission can be achieved in 70-80% of cases. Various groups of drugs are used for non-specific therapy of allergic diseases: antihistamines, cromons, corticosteroids, bronchodilators, etc. From non-drug methods, acupuncture, climatotherapy, homeopathy, phytotherapy are used.
The section “Allergic diseases” of this medical handbook provides information on the most common violations of immunological reactivity. These materials competently tell about modern views on the causes and features of the course of allergic diseases, as well as approaches to their diagnosis and treatment