Urticaria is characterized by the appearance of wheals (hives) and/or angioedema.
The intensity of the pruritus varies but may be severe enough to disrupt sleep, work or school.
It is classified acute if the urticaria has been present for ≤6 weeks and chronic if >6 weeks. It can be spontaneous (no definite triggering factor) or inducible (a specific definite triggering factor is identified).
It can be triggered by immunological or non-immunological mechanism.