Allergy and Immunology
Core concepts
Understand type I hypersensitivity (IgE-mediated, mast cell degranulation) as the basis of allergic rhinitis, asthma, and anaphylaxis. Know the allergic rhinitis classification (intermittent vs persistent, mild vs moderate-severe) and treatment ladder: allergen avoidance, intranasal corticosteroids (most effective), antihistamines, and immunotherapy for refractory cases. Recognise anaphylaxis (airway, breathing, circulation, skin) and treat with intramuscular adrenaline first-line, repeated as needed, plus airway support. Know skin prick testing and specific IgE as diagnostic adjuncts - history remains central. Understand drug allergy patterns and immunodeficiency red flags (recurrent severe infections, failure to thrive, family history).
Traps
Do not use antihistamines as first-line for anaphylaxis - adrenaline is. Intranasal steroids are more effective than antihistamines for rhinitis. A negative skin test does not always exclude allergy; correlate with history. Beware confusing anaphylaxis with vasovagal or panic.
Rule of thumb
Anaphylaxis = IM adrenaline into the anterolateral thigh immediately, then airway/breathing/circulation support. For rhinitis, intranasal corticosteroid is the most effective single agent.