A large percentage of chronic hives are not caused by allergies, they are idiopathic meaning doctors do not know the cause. I had chronic idiopathic urticaria (hives) for about 5 years. It was not an allergy, it was not a disease, it was not from stress. I had every test and took every medicine available. I spent a lot of money over the course of several years. I read that some studies believe it is auto-immune. Hydroxyzine was the only thing that sort of helped. Then, suddenly and mysteriously, they went away. I had them almost daily for years, anything that scratched or sometimes even touched my skin would trigger them. There was never an explanation. I didn't move, change jobs, change soaps, change fooRAB, nothing. It has now been several years since I had them. Sometimes I wonder if it is lurking somewhere ready to strike again. For now I am itch free.