Allergy - HS type I

Question 1

What type of hypersensitivity is allergy?

Answer 1

Type I

Question 2

What immunoglobulin is involved in allergic reactions and explain how they cause a reaction?

Answer 2

Antigen specific IgE antibodies

Mast cell expresses receptors for IgE, allergen cross links IgE bound to mast cells, causing mast cell degranulation

Question 3

How does an allergic reaction differ from a normal adaptive immune response?

Answer 3

Normal - TH1 cells produce IgG antibodies

Allergy - TH2 cells produce IgE antibodies

Question 4

Where are mast cells found?

Answer 4

Produced in bone marrow
GI tract
Skin (dermis and epidermis) 
Resp. epithelium
Connective tissue

Question 5

Name the mast cell mediators and their function

Answer 5

Histamine - increased vascular permeability and bronchoconstriction
Leuokotrines - smooth muscle contraction and increased vascular permeability
Tryptase - remodels connective tissue
Platelet activating factor - attracts leukocytes

Question 6

Define anaphylaxis

Answer 6

Systemic activation of mast cells, a type I hypersensitivity reaction

Question 7

Describe the systemic features of anaphylaxis

Answer 7

Generalised urticaria
Angioedema
Hypotension
Upper airway obstruction with stridor 
Lower airway obstruction with wheeze 
Cyanosis 
Palpitations 
N/V
Dizziness

Question 8

Describe the steps of treating anaphylaxis

Answer 8

-Using an epi pen to administer adrenaline intramuscularly -
Remove safety cap
Place epi pen against mid antero-lateral thigh
Inject with audible click
Hold device in for 10 s
Massage injection site for 10s

Question 9

Describe management of allergies

Answer 9

Strict avoidance of potential triggers
Epi pen training and carrying at all times
Medical alert bracelet
Referral to allergy clinic for skin prick tests
Oral reintroduction in gradual increasing amounts to desensitise

Question 10

Give a dermatological description of urticaria

Answer 10

Errythematous, well defined papules

Question 11

Describe the type of reaction that produces urticaria

Answer 11

Type I hypersensitivity reaction within the epidermis, caused by mast cell reaction

Question 12

What drugs are used to treat allergic reactions?

Answer 12

Anti histamines
Corticosteriods eg prednisolone
Leukotrine receptor antagonist
Anti - IgE monoclonal antibody

Question 13

How long does an allergic reaction take to develop?

Answer 13

<30 mins