9th June 2025

Diagnosis

Acute urticaria is often a clinical diagnosis. However, chronic urticaria can have a broader range of differentials and if there is diagnostic uncertainty skin biopsy may be warranted although the results can often be difficult to interpret. Pathology typically reveals oedema in the dermis and dilated blood vessels as well as inflammatory cells. As such, often a skin biopsy will rule out other important differentials such as urticarial vasculitis. Skin prick tests and radioallergosorbent tests (RAST) or CAP fluoroimmunoassay can be used to try to identify specific allergens if the trigger/s are unclear.