Allergies and Types of Allergic Reactions in Children
1. Mahalingam Jagadeeshwaran
2. Stephen Priyadharshini
3. Arundhathi Shaji
4. Osmonova Gulnaz
(1. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic)
(2. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic)
(3. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic)
(4. Teacher, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic)
Abstract
Allergic disorders are among the most common chronic conditions affecting children, resulting from exaggerated immune responses to otherwise harmless environmental or dietary substances. These reactions are primarily mediated by immunological mechanisms, most notably immunoglobulin E (IgE), leading to the release of inflammatory mediators such as histamine from mast cells and basophils. Allergic reactions are broadly classified into four types based on the Gell and Coombs classification, with Type I (immediate hypersensitivity) being the most clinically relevant in pediatric populations. This category includes conditions such as urticaria, angioedema, and anaphylaxis, which vary in severity from mild cutaneous manifestations to life-threatening systemic emergencies.
Anaphylaxis represents the most severe form of allergic reaction, characterized by rapid onset and involvement of multiple organ systems, including the skin, respiratory, cardiovascular, and gastrointestinal systems. Prompt recognition and immediate administration of intramuscular epinephrine are critical to prevent fatal outcomes. Urticaria, commonly known as hives, presents as transient, pruritic wheals on the skin and is often triggered by infections, foods, or medications. Angioedema, or Quincke’s edema, involves deeper dermal and subcutaneous swelling, frequently affecting the face and airway, and may occur independently or in association with urticaria and anaphylaxis.
This article provides a comprehensive overview of allergies in children, detailing the classification of allergic reactions, underlying pathophysiology, clinical manifestations, and management strategies, with particular emphasis on anaphylaxis, urticaria, and angioedema. Early diagnosis, identification of triggers, and appropriate therapeutic interventions are essential in reducing morbidity and preventing complications in pediatric patients.
Introduction to Allergies
Allergies are exaggerated immune responses that occur when the body reacts to substances (allergens) that are usually harmless to most individuals. In children, allergic diseases are particularly common due to the developing immune system and genetic predisposition. When a child with an allergic tendency is exposed to an allergen such as food proteins, pollen, dust mites, or insect venom, the immune system mistakenly identifies it as a threat and produces immunoglobulin E (IgE) antibodies. These antibodies bind to mast cells and basophils, leading to the release of chemical mediators such as histamine, leukotrienes, and prostaglandins. These mediators are responsible for the clinical symptoms of allergy, which can range from mild skin reactions to life-threatening systemic responses.
Allergic disorders in children include conditions such as asthma, allergic rhinitis, atopic dermatitis, urticaria, angioedema, and anaphylaxis. The prevalence of allergies has been increasing worldwide, possibly due to environmental factors, lifestyle changes, and reduced exposure to microbes in early life (hygiene hypothesis). Early recognition and appropriate management are essential to prevent complications and improve quality of life.
Types of Allergic Reactions
Allergic reactions are classified based on the underlying immunological mechanism. The most widely accepted classification is the Gell and Coombs classification, which divides allergic reactions into four types.
Type I Hypersensitivity (Immediate Reaction)
Type I hypersensitivity is the most common form of allergic reaction in children and is mediated by IgE antibodies. Upon first exposure to an allergen, the child becomes sensitized, and IgE antibodies are produced. On subsequent exposure, the allergen binds to IgE on mast cells, causing degranulation and release of histamine and other mediators. This leads to symptoms that occur within minutes to hours.
Common examples in children include:
Anaphylaxis, Urticaria (hives), Angioedema, Allergic rhinitis, Bronchial asthma.
These reactions are rapid in onset and can vary in severity from mild itching to severe airway obstruction.
Type II Hypersensitivity (Cytotoxic Reaction)
Type II reactions involve IgG or IgM antibodies directed against antigens on the surface of cells. This leads to cell destruction through complement activation or phagocytosis. Although less common in typical pediatric allergies, these reactions can occur in certain drug allergies or autoimmune conditions.
Examples include: Hemolytic anemia, Transfusion reactions
Type III Hypersensitivity (Immune Complex Reaction)
In Type III reactions, antigen-antibody complexes are formed and deposited in tissues, leading to inflammation and tissue damage. These reactions are less commonly seen as classical allergies in children but may occur in certain conditions.
Examples include: Serum sickness, Some drug reactions
Type IV Hypersensitivity (Delayed Reaction)
Type IV reactions are mediated by T lymphocytes rather than antibodies. These reactions occur hours to days after exposure to the allergen. They are commonly seen in contact allergies.
Examples include:
Contact dermatitis (e.g., reaction to metals, cosmetics)
Tuberculin skin test reaction
Anaphylaxis in Children
Definition and Overview
Anaphylaxis is a severe, life-threatening systemic allergic reaction that occurs rapidly after exposure to an allergen. It involves multiple organ systems, particularly the skin, respiratory system, cardiovascular system, and gastrointestinal tract. In children, common triggers include food allergens (such as peanuts, milk, eggs), insect stings, medications, and latex.
Pathophysiology
Anaphylaxis is primarily an IgE-mediated Type I hypersensitivity reaction. Upon exposure to the allergen, massive degranulation of mast cells and basophils occurs, releasing large amounts of histamine and other mediators. This leads to:
Vasodilation and increased vascular permeability → hypotension and shock
Bronchoconstriction → breathing difficulty
Mucosal edema → airway obstruction
Clinical Features
The symptoms of anaphylaxis usually appear within minutes and progress rapidly. They may include:
Skin manifestations: urticaria, itching, flushing
Respiratory symptoms: wheezing, stridor, shortness of breath
Cardiovascular signs: hypotension, tachycardia, collapse
Gastrointestinal symptoms: vomiting, abdominal pain, diarrhea
In severe cases, it can lead to anaphylactic shock, which is a medical emergency.
Management
Immediate treatment is crucial in anaphylaxis. The primary steps include:
Intramuscular adrenaline (epinephrine) – first-line treatment
Airway management and oxygen support
Intravenous fluids for hypotension
Antihistamines and corticosteroids as adjunct therapy
Children at risk should carry an epinephrine auto-injector and caregivers must be trained in its use.
Urticaria (Hives) in Children
Definition
Urticaria is a common allergic condition characterized by the sudden appearance of raised, itchy, red or pale swellings on the skin called wheals. These lesions can vary in size and shape and may appear anywhere on the body.
Etiology
Urticaria in children can be triggered by various factors, including:
Food allergens (milk, eggs, nuts)
Medications (antibiotics, NSAIDs)
Infections (viral infections are a common cause in children)
Physical stimuli (cold, heat, pressure)
Insect bites
In many cases, the exact cause may not be identified.
Pathophysiology
Urticaria results from the release of histamine and other mediators from mast cells in the skin. This leads to increased permeability of blood vessels, causing localized swelling and redness.
Clinical Features
Raised, itchy wheals with a central pale area
Lesions may change shape and location rapidly
Each lesion usually lasts less than 24 hours
May be associated with angioedema
Types of Urticaria
Acute urticaria: lasts less than 6 weeks
Chronic urticaria: persists for more than 6 weeks
Management
Identification and avoidance of triggers
Antihistamines are the mainstay of treatment
Severe cases may require corticosteroids
Angioedema (Quincke’s Edema) in Children
Definition
Angioedema is a deeper form of swelling that occurs in the dermis and subcutaneous tissues, often affecting the face, lips, eyelids, tongue, and throat. It is sometimes referred to as Quincke’s edema.
Etiology
Angioedema may occur due to:
Allergic reactions (IgE-mediated)
Medications (e.g., ACE inhibitors)
Hereditary causes (C1 esterase inhibitor deficiency)
Idiopathic causes
Pathophysiology
Like urticaria, angioedema involves increased vascular permeability due to mediator release. However, it affects deeper layers of the skin and mucosa, leading to more pronounced swelling.
Clinical Features
Sudden, non-pitting swelling of the skin
Commonly affects lips, eyelids, and tongue
May involve airway. Usually not itchy, but may be painful or tense
Complications
The most serious complication is airway obstruction, especially when the tongue or larynx is involved. This can lead to respiratory distress and requires emergency intervention.
Management
Antihistamines for mild cases, Corticosteroids for moderate to severe cases, Epinephrine if associated with anaphylaxis, Airway management in severe cases.
Conclusion
Allergic reactions in children range from mild conditions like urticaria to severe, life-threatening emergencies such as anaphylaxis. Understanding the types of hypersensitivity reactions and recognizing early symptoms are crucial for timely diagnosis and treatment. Urticaria and angioedema are common manifestations that may occur independently or as part of a systemic allergic response. Anaphylaxis requires immediate medical attention and prompt administration of epinephrine to prevent fatal outcomes. Proper education of caregivers, avoidance of known allergens, and preparedness for emergencies are essential components of managing pediatric allergies effectively.
References
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