Type I Hypersensitivity and Allergy of the Skin

Question 1

describe what an allergy is

Answer 1

hypersensitivity reaction of the immune system, when person’s immune system reacts to normally harmless substance, causing reaction called an allergy

Question 2

describe what a type I hypersensitivity reaction is and the rate it occurs at

Answer 2

immediate reaction mediated by IgE, allergic reaction occurs within minutes up to 2hours after exposure

Question 3

what are the different routes if exposure to an allergen

Answer 3

skin contact, inhalation, ingestion and injection

Question 4

what different clinical presentations can occur in a type I hypersensitivity reaction

Answer 4

anaphylaxis, urticaria, wheezing/asthma, angioedema

Question 5

describe the clinical features of urticaria

Answer 5

very itchy skin lesions, appear within 1 hour, last 2-6hours usually,

Question 6

what are some other names for urticaria

Answer 6

“hives,” ‘“nettle rash,” “hives”

Question 7

describe what angioedema is

Answer 7

localised swelling of subcutaneous tissue or mucous membranes

Question 8

what clinical features are seen with angioedema

Answer 8

non-pitting oedema, not itchy(unless associated urticaria

Question 9

what is anaphylaxis characterised by

Answer 9

rapidly developing, life-threatening problems involving; airways and/or breathing and/or circulation due to generalised or systemic hypersensitivity reaction
(usually associated with skin/mucosal changes)

Question 10

what investigations are used for type I hypersensitivity reactions

Answer 10

specific IgE, skin prick or prick-prick testing, challenge test, serum mast cell tryptase level(during anaphylaxis)

Question 11

what is the general management for type I hypersensitivity reactions

Answer 11

allergen avoidance, prevent effects of mast cell activation(anti-histamines),anti-inflammatory agent(corticosteroids), adrenaline autoinjector(for anaphylaxis)