What is an allergy?
An immune response to a normally harmless substance
What is an allergen?
A substance that triggers an allergic response
What is atopy?
A genetic predisposition to produce IgE antibodies to allergens
What antibody is central to allergic reactions?
Immunoglobulin E (IgE)
What cells are primed during sensitisation?
Mast cells
What happens during first exposure to an allergen
Sensitisation - IgE binds to mast cells
What triggers symptoms in later exposures?
Mast cell degranulation and histamine release
What type of hypersensitivity is an allergy?
Type 1 (immediate) hypersensitivity
What are two phases of an allergic reaction?
Early and late phase
When does the early phase occur?
Within minutes
What mediators are released in the early phase?
Histamine, leukotrienes, prostaglandins
When does the late phase occur?
4-12 hours after exposure
What cells dominate the late phase?
Eosinophils, neutrophils, basophils
Name 3 common types of allergens
Pollen
Foods
Drugs
Give examples of food allergens
Nuts
Eggs
Milk
Seafood
Give examples of environmental allergens
Dust mites
Mould
What does histamine do to blood vessels?
Vasodilation and increased permeability
Effect of histamine on smooth muscle?
Contraction
Effect of histamine on nerves?
Causes itching
Effect of histamine on glands?
Increases secretions eg runny nose
What is allergic rhinitis?
Inflammation of the nasal lining causes sneezing, congestion, and rhinorrhoea
What are the three types of allergic rhinitis?
Seasonal
Perennial
Occupational
What causes seasonal allergic rhinitis?
Outdoor allergens like pollen
What causes perennial allergic rhinitis?
Indoor allergens like dust mites or pets
