Allergic Diseases

Question 1

Definition of allergy and hypersensitivity

Answer 1

Undesirable, damaging, discomfort-producing and sometimes fatal reactions produced by the normal immune system directed against the innocuous antigens in a pre-sensitised (immune) host

Question 2

Type I hypersensitivity overview

Answer 2

Anaphylactic hypersensitivity involving IgE
Exogenous antigen
15-30 minutes
Causes wheals and flares
Basophils and eosinophils involved
Antigen example = pollen
Disease example = allergic asthma

Question 3

Type II hypersensitivity overview

Answer 3

Cytotoxic hypersensitivity
Cell surface antigen
Involving IgG, IgM
Minutes-hours
Causes lysis and necrosis
Antibody and complement involved
Antigen example = penicillin
Disease example = erythroblastosis fetalis

Question 4

Type III hypersensitivity overview

Answer 4

Immune-complex hypersensitivity
Involving IgG, IgM
Soluble antigen
3-8 hours
Causes erythema, oedema, necrosis
Complement and neutrophils involved
Antigen example = mouldy hay
Disease example = SLE, serum sickness

Question 5

Type IV hypersensitivity overview

Answer 5

Delayed type hypersensitivity
No antibodies involved
Tissue and organ antigen
48-72 hours
Causes erythema induration
Monocytes and lymphocytes involved
Antigen example = TB test, poison ivy
Disease example = contact dermatitis

Question 6

Immune response to parasitic disease

Answer 6

Increased IgE
Tissue inflammation with eosinophilia & mastocytosis, as well as basophil infiltration
Presence of CD4+ T cells secreting IL4, IL5 and IL13

Question 7

Genetic influence on allergic disease

Answer 7

All polygenic

Only susceptibility, not cause

Question 8

IgE production

Answer 8

Th2 cell triggers B cell with IL4 which then proliferates, producing IgE

Question 9

Role of Th2 cell

Answer 9

Multiple cytokine release
Innate inflammatory response
Drive for immunoglobulin production

Question 10

Atopic triad

Answer 10

Asthma, rhinitis, eczema

Question 11

Two main groups of rhinitis

Answer 11

Allergic and non-allergic

Question 12

Types of allergic rhinitis

Answer 12

Seasonal (pollen, moulds)

Perennial (house dust mite, animal dander)

Question 13

Types of non-allergic rhinitis

Answer 13

Vasomotor
Infective
Structural
Drugs
Hormonal
Polyps

Question 14

Asthma

Answer 14

Inflammation and hyper-reactivity of small airways
Immediate symptoms are always IgE-mediated, damage to airways always due to late phase response.
Damaged airways are hyper-reactive to non-allergic stimuli eg. fumes

Question 15

Three classes of dermatitis

Answer 15

Eczema (can be atopic or non-atopic), contact dermatitis (allergic or non-allergic), other dermatitis

Question 16

Common allergy tests

Answer 16

Specific IgE testing

Skin prick test

Question 17

Advantages and disadvantages of specific IgE testing

Answer 17

A - Safe

D - False negatives, false positives

Question 18

Advantages and disadvantages of skin prick test

Answer 18

A - Quick, patient satisfaction

D - False negatives, false positives, antihistamines, slight risk

Question 19

Types of adverse food reaction

Answer 19

Food intolerance (based on food characteristic e.g. caffeine or toxin) or host characteristic (e.g. lactase deficiency or psychological)
Food allergy (IgE mediated inc anaphylaxis, mixed, or non IgE mediated)

Question 20

Treatment of allergy

Answer 20

Symptomatic: Antihistamines, steroids, adrenaline
Specific: Immunotherapy

Question 21

Indications for immunotherapy

Answer 21

Life threatening reactions to wasp and bee stings
Severe hay fever
Animal dander allergy

Question 22

Contraindications for immunotherapy

Answer 22

Multiple allergies
Food allergies
Eczema
Spontaneous urticaria

Question 23

Major food allergens

Answer 23

Cow's milk
Egg
Legumes (e.g. peanuts, soybean, tree nuts)
Fish
Crustaceans and molluscs
Cereal grains

Question 24

Clinical manifestations of adverse reactions to food

Answer 24

Gastrointestinal: vomiting, diarrhoea, oral symptoms
Respiratory: Rhinitis, bronchospasm
Cutaneous: urticaria, angioedema
Anaphylaxis

Question 25

History for drug allergy

Answer 25

Indication for drug
Detailed description of reaction
Time between intake and onset of symptoms
Number of doses taken before onset
Aware of pharmacological effects and non-immunological ADR

Question 26

Management of drug allergy

Answer 26

Intradermal testing (maybe contraindicated in some situations)
Graded challenge
Desensitisation