Hi! When I learned about Allegra Hives I sought it out to control a current flare-up. It worked, but when I went to purchase more I took a moment to compare it to regular Allegra. They all seem to be the same product (Fexofenadine Hydrochloride), just in varying dosages. The two products I have on hand right now are Allegra 24 hr, which contains 120 mg of Fexofenadine HCl, and Allegra Hives 24 hr, which contains 180 mg. So, I am using them interchangeably.
I find I'm having to increase my dosage somewhat; in a previous bout I was using three or four times the recommended dosage of antihistamine, with the approval of my doctor, who said that it was acceptable due to the high levels of histamine in my system. (I am not suggesting anyone exceed recommended dosages WITHOUT medical approval, I'm just sharing my experience.)
Hope that helps!