Immunology - Hypersensitivity Disorders Flashcards
What are Type 1 Hypersensitivity reactions?
- Immediate reaction provoked by re-exposure to an antigen
- IgE-mediated: Mast cells release mediators resulting in vasdilation, increased permeability, smooth muscle spasm
What are some typical Sx of a Type 1 Hypersenstivity reaction?
- Angioedema
- Urticaria
- Rhino conjunctivitis
- Wheeze
- D+V
- ANAPHYLAXIS
What happens on first and second exposure in a Type 1 Hypersensitivity reaction?
First Exposure: Sensitisation
- Th2 cells primed by APCs in LN
- Cytokine release (IL4 + IL5)
Second Exposure: Allergy
- Primed mast cells degranulate
- Histamine = key mediator
- Ag cross-links IgE on mast cells resulting in degranulation
What is the atopic triad?
- Eczema
- Asthma
- Hay fever
What are the allergens in atopic dermatitis (infantile eczema)?
- Irritants
- Food
- Environmental
What is the pathology of atopic dermatitis (infantile eczema)?
Defects in β defensin predisposes to S. aureus superinfection
How is atopic dermatitis diagnosed?
Clinical
- 80% present in first year of life
How is atopic dermatitis managed?
- Emollients
- Skin oils
- Topical steroids
- Abx
- PUVA phototherapy
What are the typical allergens for a food allergy?
- Milk
- Egg
- Peanuts
- Tree nuts
- Fish
- Shellfish
What is the pathology of a food allergy?
- IgE (anaphylaxis)
- Cell mediated (Coeliac)
- IgE/Cell mediated (atopic dermatitis)
How is a food allergy diagnosed?
- Food diary
- Skin prick tests
- RAST
- Challenge test
Most resolve by adulthood
What is the treatment for a food allergy?
- Dietician
- Food avoidance
- EpiPen
- Control asthma if present
What are some allergens for Oral Allergy Syndrome (OAS)?
- Birch pollen + rosacea fruit
- Ragweed + melons
- Mugwort + Celery
Cross-reactivity
What is the pathology of an oral allergy syndrome?
- Exposure to allergen induces allergy to food
- Sx limited to mouth (2% get anaphylaxis)
How is Oral Allergy syndrome diagnosed?
- Clinical Dx
- Skin prick testing can be helpful
How is Oral Allergy Syndrome Treated?
- Avoid food
IF ingested:
- Wash mouth
- Take antihistamine
What are some allergens for latex food syndrome?
- Chestnut
- Avocado
- Banana
- Potato
- Tomato
- Kiwi
- Papaya
- Eggplant
- Mango
- Wheat
- Melon
What is the pathology of a latex food syndrome?
- Some foods have latex-like components
- Latex allergy sufferers also have food allergies
How is latex food syndrome diagnosed?
Skin prick test
What is the treatment for latex food allergy?
Strict avoidance of causative food
What are some allergens for Allergic rhinitis?
Seasonal
- Tree + grass pollen
- Fungal spores
Perennial
- Pets
- House dust mite
Occupational:
- Latex
- Lab animals
What are some Sx of allergic rhinitis?
- Nasal itch + obstruction
- Sneezing
- Anosmia
- Eye Sx
How is allergic rhinitis diagnosed?
- Pale bluish nasal mucosa
- Skin prick test + RAST
What is the treatment for allergic rhinitis?
- Allergen avoidance
- Antihistamine
- Steroid nasal spray
- Sodium Cromoglycate Eye drops
- Oral steroids
- Ipatropium nasal spray