Allergy Flashcards
What is the incidence of asthma in the UK?
9.4%
What is the incidence of allergic rhinitis in the UK?
5.4%
What is the incidence of eczema in the UK?
1%
What is the incidence of food allergies in the UK?
1-2%
What is the incidence of multiple allergies in the UK?
3.7%
When did the rapid increase in allergies in the UK begin?
1960s
What is the financial cost of treating allergic disorder in a year in Scotland?
£130 million
Allergy
-A hypersensitive disorder of the immune system
What do allergic reactions occur normally to?
- Harmless environmental substances known as allergens.
- These reactions are acquired
Allergic reaction
An exaggerated or inappropriate immune reaction and causes damage to the host
What are common allergic reactions?
- Eczema
- Allergic rhinitis
- Asthma
- Food allergies
Allergen
Antigen that causes allergic reactions
What are allergens usually?
Proteins
Systemic or localised symptoms are dependent on?
- Individual
- Allergen
- Mode of introduction
Where is asthma localised to?
Respiratory system
Where is eczema localised to?
Dermis
Give examples of fairly common food allergens.
- Peanuts
- Eggs
- Milk
- Dairy
Give examples of less common food containing allergenic proteins.
- Soy
- Wheat
- Fish
- Shellfish
- Fruits
- Vegetables
- Spices
What are common symptoms of an allergic reaction.
- Sneezing
- Nasal congestion
- Runny nose
- Swelling and tenderness of the mouth
- Difficulty breathing
- Flushing or rash
- Burning and itching of the skin
- Hives
- Nausea/vomiting
- Abdominal cramps
- Diarrhoea
What is the pathophysiology of allergy?
IgE mediated triggering of mast cells and subsequent accumulation of inflammatory cells at sites of antigen deposition
What happens on first exposure to allergen?
- Response with T cells and B cell producing IgE
- IgE circulates in the blood and binds to an IgE specific receptor
What is the acute response on exposure to allergen?
- Ag+ specific IgE
- Degranulation with release of histamine, cytokines, interleukins, leukotrienes and prostaglandins from their granules causing systemic effects such as vasodilation, mucous secretion, nerve stimulation and smooth muscle contraction
When does the late phase response occur on exposure to allergen?
2-4 hours later
What is the late phase response to allergen due to?
Migration of other leukocytes such as neutrophils, lymphocytes , eosinophils and macrophages to the initial site
What are the host related risk factors for allergen?
- Hereditary
- Race
- Age
What are the environmental related risk factors for allergen?
- Alterations in exposure to infectious diseases during early childhood
- Environmental pollution
- Allergen levels
- Dietary changes
How is an allergy diagnosis made?
- Skin test: responses to known allergens- high NPV, up to 15% false positives
- RAST: presence an levels of allergen-specific IgE
What different modalities of treatment are there for allergies?
- Allergen avoidance
- Immunotherapy
- Pharmacotherapy
What is the traditional treatment for allergies?
Avoidance
What is involved in avoiding allergens?
- Avoiding or reducing exposure to the allergen in question
- Cat allergies: easy to avoid cats but difficult to avoid air-borne allergies
Why are drugs used the treatment of allergies?
To prevent activation of cells and degranulation processes or to block the action of allergic mediators
What drugs can be used in the treatment of allergies?
- Antihistamines
- Glucosteroids
- Epinephrine
- Theophylline
- Cromolyn sodium
- Antileukotrines
What is involved in immunotherapy?
Controlled exposure to known allergens to reduce the severity of allergy
What is immunotherapy useful in?
- Allergic rhinitis
- Allergic asthma
- Allergic conjunctivitis
What is immunotherapy not useful in?
- Food allergy
- urticarial
- Atopic dermatitis
How does immunotherapy work?
- Desensitization: vaccinated with progressively larger doses of the allergen
- Increasing IgG antibody production blocks excessive IgE production
- The person builds up immunity to increasing amounts of the allergen in question
Allergic rhinitis
Allergic inflammation of the nasal airways
When does allergic rhinitis occur?
When an allergen is inhaled by an individual with a sensitized immune system
What are the clinical features of an allergic response?
- Sneezing
- Coughing
- Wheezing
- Runny nose
- Weepy eyes
- Itchiness
What are the classifications of allergic rhinitis?
- Seasonal
- Perrennial
