Why does urticaria always break out repeatedly

Urticaria is a skin disease induced by mast cell degranulation and histamine release. There are many reasons for mast cell degranulation. If mast cell degranulation is induced by physical factors, such as heat or cold or mechanical stimulation, such as exercise, vibration, friction, pressure, etc., urticaria is very difficult to cure completely. It requires patients to take medicine for a long time to control it. Clinically, it will be manifested as repeated attacks. There is also a type of urticaria because the patient is exposed to an allergen, showing symptoms of urticaria, but the patient does not find this allergen, and his life will be repeatedly exposed to this allergen, so it will show repeated episodes of chronic urticaria.