Urticaria and Itch

Question 1

What is urticaria?

Answer 1

Transient (lesion <24 hours) eruption of erythematous + oedematous swelling of dermis
–> nettle rash, hives, weals
ITCHY

Question 2

What is angio-oedema?

Answer 2

Urticaria of mucous membranes

Question 3

What are some causes of urticaria?

Answer 3

Allergy - specific IgE mediated
Direct chemical effects - drugs e.g. aspirin, codeine
Physical
Autoimmune

Question 4

What are some physical causes of urticaria?

Answer 4

Dermographism - 'drawing on the skin'
Delayed pressure
Vibration
Aquagenic
Solar
Cold
Cholinergic e.g. after exercise

Question 5

What are the causes of angio-oedema?

Answer 5

All the causes of urticaria
C1 esterase inhibitor deficiency (doesn’t cause urticaria as not mast cell mediated)
ACE inhibitors

Question 6

What are the possible ways ACE inhibitor induced angio-oedema can present?

Answer 6

On skin/mucus membranes

As abdominal pain due to small bowel angio-oedema

Question 7

How is urticaria managed?

Answer 7

Avoid cause if possible
Suppression:
- antihistamines
- UV phototherapy (makes mast cells less ready to degranulate)

Question 8

What are the different types of itch/pruritis?

Answer 8

Pruritoceptive - something in the skin e.g. dryness, inflammation
Neuropathic - damage to CNS or PNS e.g. MS, herpes zoster
Neurogenic - no damage in CNS but caused by CNS effects e.g. opiates
Psychogenic e.g. delusions of infestation

Question 9

How is itch managed?

Answer 9

Determine and treat cause
Anti itch treatment:
- SEDATIVE antihistamines
- emollient with menthol or cooled in fridge
- antidepressants e.g. doxepin
- phototherapy
- opiate antagonists e.g. ondansetron

Question 10

When are non-sedative antihistamines useful for itch?

Answer 10

Urticaria or insect bites

Don’t help other types as don’t cross BBB

Question 11

What is the best treatment for itch caused by CKD?

Answer 11

UVB phototherapy