Urticaria

Urticaria can be acute or chronic. The acute form lasts less than 6 weeks and is usually due to infection or allergy. The chronic form lasts more than 6 weeks and is most commonly spontaneous in nature or secondary to physical causes such as exposure to the heat, cold, pressure over the skin or exercise. Less commonly, it can be triggered by other internal causes such as autoimmune disease, Helicobacter pylori infection, lymphoma or thyroid disorder.