Urticaria and pruritus

Question 1

What is urticaria?

Answer 1

Transient eruption of erythematous and oedematous swellings of the dermis, usually itchy. Can be acute (less than 6 weeks) or chronic (more than)

Question 2

How does urticaria occur?

Answer 2

Mast cell degranulation, leading to release of vasoactive substances and transient leakage of fluid into the tissues

Question 3

Types of physical urticarias? (6)

Answer 3

Cold
Solar
Heat
Cholingergic (anxiety, sexual excitement, strenuous exercise)
Dermograpism (commonest)
Delayed pressure urticaria

Question 4

Latex allergy is a type of what?

Answer 4

Contact urticaria

Question 5

What is angioedema?

Answer 5

Transient swelling in the deeper dermal, subcutaneous and submucosal tissues

Question 6

What drugs can commonly cause angioedema?

Answer 6

ACE inhibitors

Question 7

What is the mainstay of urticaria treatment?

Answer 7

Anti-histamines

Question 8

Sedating antihistamines (2)

Answer 8

Chlorphenamine

Promethazine

Question 9

Non-sedating antihistamines

Answer 9

Cetirizine
Loratadine
Fexofenadine

Question 10

What is the definition of anaphylaxis?

Answer 10

Acute angioedema, often with urticaria + respiratory compromise and hypotension

Question 11

Management of anaphylaxis

Answer 11

A- Ensure airway patency and remove any possibly-responsible food allergen
B- high flow oxygen
C- IM adrenaline 0.5-1ml of 1:1000 dilution, repeat at 15 minute intervals

Also IV antihistamine, IV hydrocortisone, consider pushing fluids

Question 12

How should peanut ingestion by a known peanut-allergic patient be treated?

Answer 12

Activated charcoal

Question 13

4 types of itch?

Answer 13

Pruritoceptive
Neuropathic
Neurogenic
Psychogenic

Question 14

Example of a type of neurogenic itch?

Answer 14

Opiate effects on CNS receptors

Question 15

How does neurogenic itch differ from neuropathic?

Answer 15

Neurogenic- no evident damage to nervous system

Neuropathic- damage to central or peripheral nerves

Question 16

Fibres responsible for mediation of itch?

Answer 16

Unmyelinated C fibres

Question 17

Chemical mediators of itch? (4)

Answer 17

Histamine
Tryptase
IL-2
substance P

Question 18

Anti-itch treatments? (5)

Answer 18

Sedative antihistamines
Emollients with menthol
Opiate antagonists
Antidepressants
Phototherapy