Urticaria
Acute Urticaria
Chronic Urticaria
Physical Urticaria
Acute Urticaria
Type I hypersensitivity or an urticarial reaction lasting up to 12 weeks.
Patients are usually aware of the precipitating cause.
Chronic Urticaria
By definition this is urticaria that has persisted for over three months. There is unlikely to be an allergic cause and there is increasing evidence that chronic urticaria is auto-immune. Advise patients to avoid all Aspirin and Codeine containing drugs which may aggravate chronic urticaria. There is no need to refer patients with chronic urticaria for allergy testing.
Investigations: FBC, Renal, Liver, Thyroid, Antinuclear antibodies, Immunoglbulins, MSU, CXR, mandibular XR (if dental abscess suspected), ASO titre.
Almost invariably normal/negative but reassuring!
Physical Urticaria
Eg: Dermographism.
Many other physical factors may induce urticaria:
Cold
Heat
Pressure
Water
Cholinergic
Sun
Vibration
Dermographism can easily be demonstrated by firm stroking of the skin with the thumbnail and whealing resulting in five to ten minutes. Treat with non-sedating anti-histamines.
Treatments
Alone or combinations of: -
Non sedating antihistamines- Zirtec 10-20 mg od, Telfast 180mg od, Xyzal 5-10mg od, Neoclarityn 5-10mg od.
Sedating antihistamines at night- Atarax25-50mg, Phenergan 25-50mg
H2 receptor antagonists- Ranitidine 150mg bd, Cimetidine 400mg bd
Montelukast- 10mg od
Which Patients to Refer?
Refer when diagnosis is in doubt or the above treatment options are ineffective.