Allergy Flashcards
What is an allergy?
Hypersensitivity disorders the immune system
What does an allergy cause?
Inappropriate or exaggerated immune reaction, causing damage to the host
What do allergic reactions normally occur against?
Allergens- harmless environmental substances, usually proteins
What causes variation in the symptoms of an allergy?
Individual
Allergen
Mode of introduction
What is an allergic reaction of the skin called?
Urticaria/angiodema
What is an allergic reaction of the upper respiratory tract called?
Rhinitis
What is an allergy of the lower respiratory tract called?
Asthma
What is a systemic allergic reaction called?
Anaphylaxis
What is the pathology of an allergy?
Hypersensitivity due to IgE antibodies
What happens in the sensitisation stage of a hypersensitivity reaction?
Plasma cells produce IgE against allergen, which then bind to mast cells
What happens in the re-exposure phase of a hypersensitivity reaction?
IgE activated and mast cells degranulate and causes allergic reaction
What does mast cell degranulation release?
Histamine
Leukotrines
Prostaglandins
Chromotactic factors
What does mast cell degranulation physiologically cause?
Vasodilation
Vascular permeability
Smooth muscle contraction
Leukocyte infiltration
What is the late phase response?
Migration of leukocytes to initial site 2-4 hours after insult
What are the risk factors for an allergy?
Hereditary, race, age
Exposure to infectious disease as child, pollution, allergen levels, dietary changes
Flour, latex, wood dust
What is allergic rhinitis?
Allergic inflammation of nasal airways
When does allergic rhinitis occur?
Allergen inhaled by individual with sensitised immune system
What are the risk factors for allergic rhinitis?
Atopy, family history, 1st born
Exposure to infectious disease as child, pollution, allergen levels, dietary changes
What are the immediate symptoms of allergic rhinitis?
Sneezing
Itch
Nasal blockage
Rhinorrhoea
What are the late symptoms of allergic rhinitis?
Chronic obstruction
Hyposmia
Hyperreactivity
What are the classifications of allergic rhinitis?
Intermittent vs persistent
Mild vs moderate/severe
What is classified as intermittent allergic rhinitis?
Symptoms for < 4 days per week for < 4 consecutive weeks
What is classified as persistent rhinitis?
Symptoms for > 4 days a week for > 4 weeks
What is classified as mild rhinitis?
Symptoms present but not troublesome
What is classified as moderate/persistent rhinitis?
Sleep disturbance
Impairment of daily activities, school or work
Troublesome symptoms
How is an allergy diagnosed?
Skin test RAST Total serum IgE Nasal allergen challenge Nasal cytology
What is tested in a skin test?
Response to known allergens
What is tested in RAST?
Presence and levels of allergen specific IgE
What is a normal and hypersensitive IgE level?
<0.35= normal >0.35= hypersensitivity
How is an allergy treated?
Allergen avoidance
Pharmacologically
Possible immunotherapy and surgery
How can an allergy be treated pharmacologically?
Topical intranasal steroids Systemc steroids Antihistamines Sodium cromoglycate Allergen immunotherapy Anti IgE
