I have hives like you describe and they've occurred either when I'm under a lot of stress, or right after the stress has been resolved (or I think it has been). They last a few months and resolve themselves. I asked a psychologist friend of mine why I would get hives after a stressful event and he said it was probably that my cortisole levels were elevated during stress, and then dropped to unnaturally low levels after the stress, which compromised my immune system. At the beginning of my last bout with hives (which I've had for a week now) I also had a fever blister in my mouth and really bad trigger points in my muscles, causing a lot of pain in the muscles of my back. All of these may be autoimmune responses to the drop in cortisole... or, I suppose, to an elevation of cortisole when I get hives when I'm under stress. I'm currently on prednisone because I had a few develop in my mouth, but generally, I take a combination of an OTC antihistimine, like generic Claritan, and a H2 Blocker (if I'm remembering the term correctly), like generic Tagamet, which is more often taken for heartburn, but also works to block histimines when taken with an antihistimine. It doesn't get rid of the hives, but it helps with the itching.