Chapter 33: Managing Allergic Disorders

The assessment and management of allergic disorders, which arise from inappropriate and often harmful immune responses to generally harmless substances (allergens), necessitate a detailed understanding of hypersensitivity reactions. Physiological responses involve B lymphocytes differentiating into plasma cells to secrete immunoglobulins, particularly IgE, which binds to mast cells or basophils, triggering the release of potent chemical mediators like histamine, leukotrienes, bradykinin, and serotonin. These reactions are categorized into four types: Type I (Anaphylactic, immediate, IgE-mediated, characterizing disorders like allergic rhinitis and asthma, and the severe, life-threatening reaction, anaphylaxis); Type II (Cytotoxic, involving IgG or IgM attacking cell antigens, such as in hemolytic transfusion reactions); Type III (Immune Complex, where deposited antigen-antibody complexes cause inflammation, seen in conditions like rheumatoid arthritis); and Type IV (Delayed, T cell-mediated, manifesting in disorders like allergic contact dermatitis). Diagnosis relies on a comprehensive patient history and physical examination, supported by laboratory findings such as eosinophilia and elevated total serum IgE levels, and confirmed using specialized procedures like skin testing (prick, scratch, or intradermal) or the serum-specific IgE test. Immediate management of anaphylaxis requires rapid administration of epinephrine to counteract bronchospasm and hypotension, with adjunct therapies including antihistamines and corticosteroids; avoidance of the offending allergen and carrying an autoinjector are crucial preventive measures. Treatment for localized disorders like allergic rhinitis involves avoidance measures (e.g., HEPA filters, air conditioning), pharmacotherapy including highly effective corticosteroid nasal sprays, nonsedating second-generation antihistamines, and mast cell stabilizers; cautionary use of decongestants is advised due to the risk of rebound congestion (rhinitis medicamentosa). Long-term treatment often incorporates allergen immunotherapy (AIT), via subcutaneous (SCIT) or sublingual (SLIT) routes, to increase tolerance to specific antigens, although this procedure carries a risk of systemic reaction, requiring careful post-administration monitoring. Other specific disorders covered include Atopic Dermatitis (eczema), linked to the Atopic March progression; Drug Hypersensitivity, which is the leading cause of fatal anaphylaxis and includes severe reactions like Stevens-Johnson syndrome; and Urticaria/Angioedema, distinguishing between mast cell-mediated and bradykinin-mediated forms, such as Hereditary Angioedema. Finally, food allergies and latex allergy, which can present as both immediate (Type I) and delayed (Type IV) reactions, require stringent avoidance strategies and thorough patient education on self-management.