Chronic urticaria

**Definition:** Spontaneous urticaria lasting six weeks or more.

**Inclusions:** - Chronic ordinary urticaria - Chronic spontaneous urticaria - Chronic autoimmune urticaria - Chronic urticaria due to underlying infection or infestation - Chronic urticaria due to pseudoallergy - Chronic urticaria due to other specified mechanism - Chronic urticaria of undetermined aetiology