Allergy Flashcards
Define hypersensitivity
Objectively reproducible symptoms or signs following exposure to defined stimulus at a dose tolerated by most people
Define allergy
Hypersensitivity reaction initiated by specific immunological mechanisms
This can be IgE mediated or non-IgE mediated
Define atopy
Personal and/or familial tendency to produce IgE antibodies in response to ordinary exposure to potential allergens, usually proteins
Strongly associated with eczema, asthma, allergic rhinitis, food allergy
Define anaphylaxis
Serious allergic reaction with bronchial, laryngeal or cardiovascular involvement that is rapid in onset and may cause death
Briefly describe the Pathophysiology of allergy
Development of abnormal immune response to harmless stimuli
Immune system sensitisation on first exposure to an allergen, allergic immune response occurs on re-exposure
Immune response can be IgE mediated or non-IgE mediated
IgE mediated: early phase response, late phase response (4-6hrs later)
Non-IgE mediated: delayed onset and variable clinical course
List some allergens
Inhalant: pollen, house dust mite, pet dander, moulds
Ingestant: cows milk, eggs, nuts, soya, wheat, seeds, legumes, seafood, fruits
Insect bites, drugs, natural rubber latex
What is the hygiene hypothesis?
Explains that the Rapid increase in prevalence of allergic diseases is due to environmental changes in modern living conditions
Small family size, low exposure to parasites, infection and farming, high antibiotic exposure
Lead to reduced microbial exposure
What is the allergic march?
Development of individual allergic disorders at different ages
Infancy: food allergy, eczema
Childhood: allergic rhinitis, asthma
Presence of eczema/food allergy is predictive of asthma and allergic rhinitis in later life
Distinguish bw food allergy and food hypersensitivity
Food allergy is when pathological immune response is mounted against a specific food protein
Food hypersensitivity is non-immunological reaction to specific food
What are the clinical features of food allergy?
IgE mediated:
Acute features: urticaria, facial swelling, wheeze, stridor, abdo pain, V+D, shock, collapse
Skin prick test positive
Non-IgE mediated:
Delayed onset GI features: loose stools, D+V, faltering growth, eczema
Skin prick test negative
Elimination of allergen improves symptoms and return on trial re-introduction
What is involved in making a diagosis of food allergy?
History
IgE mediated:
Skin prick testing
ELISA - food specific IgE antibodies
Non-IgE:
Upper and lower GI endoscopy
Both:
Elimination of allergen and Double-blind Placebo-controlled food allergen challenge
What is the management for food allergy
Avoid relevant foods - Paediatric dietician
Education + self-management plans for allergic attacks
Mild: non-sedating antihistamines
Severe: IM epinephrine by autoinjector (cardiorespiratory symptoms)
Clinical features of eczema
Erythematous, weeping, pruritic lesions
Secondary changes - excoriation, lichenification, infection
Distribution :
Infant - cheeks, scalp, elbows, knees
Child - flexures, wrists, ankles
Adolescent - flexures, head, neck, palms, soles
Management of eczema
Avoid irritants - no soap, cotton garments, nails short
Emollients - 2-3/day and after shower
Topical steroids - daily until clear then taper off, avoid potent steroid on face and groin
Topical immunomodulators - tacrolimus, If not improving
Wet bandages - for scratching and lichenification
Topical antibiotics/antivirals - suspected infection
Sedative antihistamines - for sleep
Management of allergic rhinitis
Non sedating antihistamines
Intranasal corticosteroid
Montelukast (leukotrienes receptor antagonists)
