Allergy Flashcards
What are the different clinical presentations of allergic disorders?
- depends on where you develop the disorder*
- Skin: Urticaria/Angioedema
- GI: Food allergies
- Resp: Allergic Rhinitis/Asthma
- Systemic: Anaphylaxis
What is the definition of an Allergy?
- A Hypersensitive immune disorder to normally harmless environmental substances (allergens)
- These reactions are acquired
- Causes damage to the host
What is the pathophysiology of Allergic disorders?
- Type 1/Immediate Hypersensitivity reaction
- IgE mediated on re-exposure to allergen
- Sensitisation:
- > plasma cells produce IgE on first exposure to allergen
- > IgE binds to mast cells
- Re-exposure:
- > mast cells (with allergen-specific IgE) degranulate on re-exposure to the same antigen
- > releases histamine, leukotrienes, prostaglandins, + chemotactic factors
What are the risk factors for Allergic Rhinitis?
- Atopy
- FH
- 1st born
- Environmental factors:
- > alterations in exposure to infectious diseases during early childhood
- > environmental pollution
- > allergen levels
- > dietary changes
What are the clinical features of Allergic Rhinitis?
- Always with Asthma + Atopic Dermatitis (Triad)
- Immediate:
- > sneezing
- > itch
- > nasal blockage
- > rhinorrhoea
- Late:
- > chronic obstruction
- > hyposmia
- > hyper-reactivity
What are the clinical effects of mast cell degranulation?
Releases histamine, leukotrienes, prostaglandins, chemotactic agents
clinical effects:
- sneezing
- cough
- wheeze
- runny nose
- weepy eyes
- itchiness
What is the immediate and late response of allergen exposure?
Releases histamine, leukotrienes, prostaglandins, chemotactic agents
Immediate:
- antigen-specific IgE release
- vasodilation
- increased vascular permeability
- mucus secretion
- nerve stimulation
- smooth muscle contraction
Late: (2-4 hours later)
- leukocyte infiltration (esp. eosinophils)
Why does Allergic Rhinitis occur?
- Allergic inflammation of the nasal airways
- Occurs when an allergen is inhaled by an individual with a sensitised immune system
What is the ARIA classification for Allergic Rhinitis?
- Intermittent: symptoms <4 days/week or <4 consecutive weeks
- Persistent: >4 days/week and >4 consecutive weeks
- Mild: (all of the following)
- > normal sleep
- > no normal impairment of daily activities, sport, leisure
- > no impairment of work or and school
- > symptoms present but not troublesome
- Moderate-severe: (one or more items)
- > sleep disturbance
- > impairment of daily activities, sport, leisure
- > impairment of school or work
- > troublesome symptoms
may also be seasonal (ie. due to hayfever) or perennial (all year long) (ie. due to house dust mites)
How do you make the diagnosis of Allergic Rhinitis?
- History and Examination: usually enough!
- Skin test: response to known allergens (high NPV)
- RAST: presence + levels of allergen-specific IgE in the serum -> >100 kU/L specific IgE
- Other tests: total serum IgE, nasal allergen challenge (gold standard, but rarely done), nasal cytology
What are the different types of Rhinitis?
- Allergic: seasonal, perennial or episodic (IgE-mediated)
- Nonallergic: vasomotor (irritants), infectious, hormonally induced (pregnancy, menstrual cycle), gustatory (eating), granulomatous, drug-induced
- Occupational: allergic (workplace allergen) or non-allergic (irritant)
- Mixed: both IgE-mediated and nonallergic triggers
What is the treatment of Allergic Rhinitis?
- Education
- Allergen avoidance
- Pharmacotherapy:
- > antihistamines - (1st line in intermediate + persistent mild)
- > topical/systemic steroids - (topical = 1st line in persistent moderate-severe)
- > sodium cromoglycate
- Immunotherapy
- > anti-IgE (ie. Omalizumab)
- Surgery
