Urticaria

Question 1

Define urticaria

Answer 1

erythematous, blanching, oedematous, non-painful, pruritic lesions that typically last less than 24 hours and leave no residual markings upon resolution.

• Acute Urticaria: Episodes that occur over a period of less than 6 weeks are generally considered acute.
• Chronic Urticaria: Chronic urticaria is defined by repeated episodes of urticaria on a nearly daily basis for more than 6 weeks’ duration

Question 2

What are the causes/risk factors of urticaria?

Answer 2

• Many cases of acute urticaria and/or angio-oedema are allergic in nature and caused by an IgE-mediated reaction.
• Most common agents:
- Drugs: Penicillin, Sulphonamides, Diuretics, ACEi and NSAIDs
- Food: Milk, eggs, peanuts and shellfish. • Urticaria can also be due to an autoimmune cause. This is often the aetiology in chronic urticaria, which is often idiopathic. Less than 10% of patients with chronic urticaria will have an identifiable exogenous cause for the hives.
• Urticaria is a common manifestation following insect bites.
• There is often a positive family history.

Question 3

What are the symptoms of urticaria?

Answer 3

• Pruritic lesions that resolve within 24 hours.
• History-taking should aim to elicit the nature of the lesions and any specific triggers.
• Angio-oedema: Swelling of face, tongue, or lips
• Lesions can be characterised as typical or atypical.
- Typical lesions are oedematous pink or red wheals of variable size and shape, with surrounding erythema.
- Atypical lesions are purpuric, non-blanchable, and palpable. They may also leave residual pigmented skin. Atypical lesions are associated with urticarial vasculitis.
• In chronic urticaria, the lesions will occur over a period of over 6 weeks. Often, no identifiable triggers are identifiable.

Question 4

What are the signs of urticaria?

Answer 4

• erythematous oedematous lesions that may be distributed on any part of the body.
• Blanching lesions –non-blanching lesions are suggestive of a vasulitic cause of urticaria.

Question 5

What investigations are carried out for urticaria?

Answer 5

Chronic
• FBC - may provide evidence of occult infection, anaemia, or findings suggestive of chronic illness.
• Complete Metabolic Panel - may provide evidence of chronic illness, such as hepatitis or nephritis.
• Urinalysis - non-specific test that should be considered if performing a laboratory evaluation for chronic urticaria with or without angio-oedema, especially in women.
• ESR - elevated
• Anti-IgE Receptor Antibody - positive in autoimmune-related chronic urticaria.
• TSH - may reveal evidence of underlying thyroid dysfunction.
• Antithyroid Antibodies - may reveal evidence of underlying thyroid dysfunction.
• ANA - may provide evidence of underlying rheumatological disorder.
• Skin Biopsy - sample is sent for standard staining, but immunofluorescence studies may also be requested

*Laboratory tests are not indicated in cases of acute urticaria, unless there are findings on history and physical examination that would indicate the lesions were atypical.