[5] Urticaria Flashcards
What is urticaria also known as?
Hives
What is urticaria?
An itchy, red, blotchy rash resulting from swelling of the superficial part of the skin
What can also occur in urticaria if there is involvement of deeper tissues?
Angiography-oedema
What can urticaria be classified into?
- Acute
- Chronic
What is acute urticaria?
Symptoms develop quickly but resolve quickly (often within 48 hours)
What is chronic urticaria?
Where the rash persists for > 6 weeks
What cause urticaria?
Activation of mast cells in the skin causing the release of histamine and other mediators
What is the effect of histamine release in the skin?
Capillary leakage causing swelling of the skin and vasodilation causing the erythematous rash
What can sometimes underly urticaria?
An identifiable trigger
In what proportion of acute urticaria cases is a trigger identified?
About half
What are some possible triggers of acute urticaria?
- Allergies
- Viral infections
- Skin contact with chemicals, nettles, latex etc.
- Physical stimuli
What allergies can cause urticaria?
- Food
- Bites
- Stings
- Medication
What physical stimuli can cause acute urticaria?
- Firm rubbing
- Pressure
- Cold
- Heat
What are the different subtypes of chronic urticaria?
- Chronic spontaneous urticaria
- Autoimmune urticaria
- Inducible urticaria
What are the triggers of chronic spontaneous urticaria?
- Medication
- Stress
- Infection
What are the triggers for inducible urticaria?
- Aquagenic
- Exercise or emotion (cholinergic)
- Exposure to cold or heat
What are the risk factors for urticaria?
- Hay fever
- Asthma
Describe a typical urticaria lesion?
Central, itchy white papule or plaque (wheal) surrounded by an erythematous flare
Are urticaria lesions uniform?
No they can vary in size and shape
What can urticaria lesions be associated with?
Swelling of soft tissues (angioedema)
How long do the individual wheals last in urticaria?
Come and go within a few hours
How is urticaria diagnosed?
Clinically
What clinical sign identifies urticaria?
Wheals only lasting a few hours
What investigations may be required in chronic urticaria?
- FBC
- ESR
- CRP
- Physical challenge e.g. cold provocation
- Patch testing/prick testing
