Hello,
Chronic urticaria is defined as
urticaria that persists
for longer than 6 weeks. In most of the cases of chronic
urticaria, the underlying pathology is idiopathic i.e. it is not linked to any cause. It is essential to rule out the presence of serious illnesses of which recurring hives can be a symptom. Examples are hepatitis, hyperthyroidism, lymphomas, collagen vascular diseases etc.
The most potent antihistamine for urticaria is probably the anti-depressant doxepin.