Atopy and Allergy

• Atopy is a genetic tendency to make IgE reactions
• Atopy clinically manifests as rhinitis, asthma, or eczema
• Laboratory findings in atopy include high total IgE levels
• Measurement of total IgE is rarely useful for diagnosis, history is more important
• IgE mediated diseases include rhinitis, asthma, urticaria, angioedema, and anaphylaxis
• Urticaria is usually due to superficial histamine release from mast cells
• Angioedema is due to histamine release in the subcutis
• 80% of allergic reactions involve urticaria and angioedema
• Chronic urticaria and angioedema are not always caused by allergy
• Allergy can cause acute urticaria and angioedema within 1 hour
• Chronic spontaneous urticaria and angioedema are not caused by allergy
• Allergy-focused history includes EATERS: Exposure, Allergen, Timing, Environment, Reproducibility, Symptoms
• Allergy is distinguished from sensitization by the presence of clinical symptoms
• Sensitization involves allergen-specific IgE without clinical symptoms
• Allergy diagnosis includes history, skin prick tests, allergen-specific IgE, food/exposure diary, and challenges
• Management of anaphylaxis involves ABC (DE), high flow oxygen, adrenaline, fluid bolus, antihistamines, and corticosteroids
• Severity of allergic reactions is influenced by allergen dose, asthma status, and exacerbating factors
• Allergy mimics for urticaria and angioedema include chronic spontaneous urticaria, chronic inducible urticaria, urticarial vasculitis, and C1 inhibitor deficiency
• C1 inhibitor deficiency leads to elevated bradykinin causing angioedema
• C1 inhibitor deficiency management includes replacing the missing protein and blocking bradykinin
• Approach to diagnosis includes evaluating the type of urticaria/angioedema, systemic symptoms, and relevant medications like ACE inhibitors