Urticaria

– occurs due to local vasodilation, increased vascular permeability, and tissue edema secondary mast cell degranulation and histamine release. This can be mediated by 4 different mechanism:

(1) immune mediated – type I hypersensitivity reaction

(2) complement mediated

(3) autoimmune mediated

(4) non-immune mediated (e.g. secondary to opiates)

 

Acute urticaria:

– symptoms lasting less than 6 weeks

– usually has an identifiable cause – detailed history of medications / supplements / environmental exposure is very important

 

Chronic urticaria:

– symptoms lasting more than 6 weeks

– usually idiopathic

 

Investigations:

No investigations should be routinely done for patients who present with acute urticaria.

Chronic urticaria can be associated with:

thyroid autoimmune disorders (thyroid function tests, thyroid antibodies)

Helicobacter pylori (urticaria resolves with successful treatment)

helminthic infections (suggested by eosinophilia)

SLE, other autoimmune disorders (ESR is normal in idiopathic urticaria)

coeliac disease (especially in children)

 

Treatment with antihistamines:

– individual response is variable and tolerance can develop, so if there is no clinical response to one antihistamine a different one should be tried

– some patients need higher doses than the ones recommended by the manufacturer

– some patients can paradoxically get worse with antihistamines

– sometimes adding a H2 antihistamine offers better control of symptoms

Treatment with steroids:

– oral steroids for 3 days (25 – 50 mg /day in adults, 1 mg/kg in children)  may shorten duration of symptoms

– long-term use is contraindicated – evidence of harm and no evidence of benefit