Acute allergic reactions are pathological conditions that arise due to hypersensitivity of the body to allergens penetrating from the outside and are characterized by the sudden development of localized or generalized allergic reactions. Localized forms include urticaria, angioedema, laryngospasm and bronchospasm, systemic – anaphylactic shock and common toxic-allergic dermatitis. Manifestations of an acute allergic reaction depend on its form, body condition, age and other factors. Therapeutic measures include allergen elimination, restoration of vital functions, administration of antihistamines and glucocorticosteroids.
T78 Adverse effects not classified elsewhere
Acute allergic reactions are diseases that develop in the presence of hypersensitivity of the immune system to allergens entering the body from the outside. Usually, signs of an allergic reaction of an immediate type with a sudden acute onset, the spread of the pathological process to various organs and tissues, and a pronounced violation of vital functions of the body are detected. According to statistics, every tenth inhabitant of our planet has ever suffered an acute allergic reaction. There are mild (localized) manifestations of hypersensitivity in the form of exacerbation of allergic rhinoconjunctivitis and limited urticaria, moderate – with the development of widespread urticaria, Quincke’s edema, laryngospasm, bronchospasm and severe – in the form of anaphylactic shock.
The development of acute allergic reactions is usually associated with exposure to foreign substances that enter the body with inhaled air (bacterial, pollen, allergens contained in atmospheric air and house dust), food, medicines, due to insect bites, when using latex, applying various inorganic and organic substances to the skin and mucous membranes.
Exogenous factors can act as provoking moments: environmental problems, bad habits, uncontrolled use of medicines and household chemicals. Endogenous risk factors include allergy-burdened heredity, stressful situations, immune disorders.
The pathological process is most often characterized by the development of an acute allergic reaction of an immediate type. In this case, IgE-mediated hypersensitivity to a problematic foreign substance that becomes an antigen is formed. The developing immune response occurs in the presence of three types of cells – macrophages, T- and B-lymphocytes. Class E immunoglobulins synthesized by B cells are located on the surface of target cells (mast cells, basophils).
Repeated entry of the allergen into the body leads to the development of an allergic reaction with the activation of target cells and the release of a large number of inflammatory mediators (this is primarily histamine, as well as serotonin, cytokines, etc.). Such an immune reaction is usually observed when pollen, food, household allergens, medicines and serums are received, manifesting symptoms of pollinosis, atopic dermatitis and bronchial asthma, anaphylactic reactions.
The mechanism of occurrence of acute allergic diseases may be due to the formation of cytotoxic, immunocomplex, cell-mediated immune reactions. As a result of pathochemical and pathophysiological changes developing after sensitization, typical symptoms of acute allergy appear.
Symptoms of allergic reactions
The mild course of acute allergic reactions is most often manifested by symptoms of allergic rhinitis (difficulty breathing through the nose, rhinorrhea, sneezing attacks) and conjunctivitis (itching and swelling of the eyelids, redness of the eyes, photophobia). This can also include the appearance of signs of urticaria on a limited area of the skin (rounded blisters, hyperemia, itching).
With a moderate course of acute allergic reactions, the lesion of the skin becomes more pronounced and is characterized by the development of generalized urticaria with the seizure of almost the entire surface of the skin and the appearance of new blisters for several days. Often, there are signs of angioedema of the Quincke with the appearance of limited angioedema of the skin, subcutaneous tissue, mucous membranes. The pathological process is more often localized in the face, affecting the lips and eyelids, sometimes occurs on the hands, feet and scrotum, can lead to swelling of the larynx and mucous membrane of the gastrointestinal tract. An acute allergic reaction with the development of inflammation of the mucous membrane of the larynx and bronchi can cause severe complications up to death from asphyxia.
The most severe consequences of hypersensitivity of the immune system are observed in the case of anaphylactic shock. At the same time, vital organs and systems of the body are affected – cardiovascular and respiratory with the occurrence of severe arterial hypotension, collapse and loss of consciousness, as well as respiratory disorders due to laryngeal edema or bronchospasm. Clinical manifestations, as a rule, develop within a few minutes after contact with the allergen, in the absence of qualified emergency care, death often occurs.
Diagnosis of acute allergic reactions involves a thorough analysis of anamnestic data (tolerability of medications and serums, previous allergic diseases), clinical manifestations of allergies (skin lesions, upper respiratory tract, signs of suffocation, fainting, seizures, cardiac disorders, etc.). An examination by an allergist-immunologist and other specialists is required: dermatologist, an otorhinolaryngologist, gastroenterologist, rheumatologist, etc.
General clinical laboratory tests (blood, urine), biochemical blood analysis are performed, according to indications – determination of rheumatoid factor and antinuclear antibodies, markers of viral hepatitis, the presence of antibodies to other microorganisms, as well as instrumental diagnostic procedures necessary in this particular case. If possible, skin tests, determination of general and specific immunoglobulins of class E, as well as other examinations used in allergology can be carried out.
Differential diagnosis of acute allergic reactions requires the exclusion of a wide range of various allergic, infectious and somatic diseases accompanied by skin manifestations, damage to the mucous membranes of internal organs, impaired respiratory and circulatory functions.
Treatment of acute allergic reactions
Therapeutic measures for acute allergic reactions should include the early elimination of the allergen, anti-allergic therapy, restoration of impaired respiratory functions, blood circulation and other body systems. In order to stop further intake of the substance that caused the development of hypersensitivity, it is necessary to stop the administration of the drug, serum or blood substitute (with intramuscular and intravenous injections, infusions), reduce the absorption of the allergen (applying a tourniquet above the injection site of the drug or insect bite, pricking this area using an adrenaline solution).
Antiallergic therapy involves the use of antihistamines and glucocorticosteroid hormones topically, orally or parenterally. The specific dosages of drugs and the method of their administration depend on the localization of the pathological process, the severity of an acute allergic reaction and the patient’s condition. Symptomatic therapy is aimed at correcting impaired body functions and, above all, respiration and blood circulation. Thus, bronchospasm is inhaled with broncholytic and anti-inflammatory drugs (ipratropium bromide, salbutamol, etc.), with severe arterial hypotension, vasopressor amines (dopamine, norepinephrine) are prescribed with simultaneous replenishment of the circulating blood volume.
In severe cases, emergency care is provided in the conditions of the intensive care unit of the hospital with the use of special equipment that supports the function of blood circulation and respiration. After the relief of acute manifestations of allergic reactions, treatment is carried out by an allergist-immunologist using an individually selected scheme of drug therapy, compliance with an elimination diet, if necessary, conducting ASIT.