I literally just went to a minute clinic in Kroger yesterday because of hives. I got some poison something (ivy, oak, sumac, who knows), and the rash has been appearing over the coarse of the last week and THEN, I broke out in hives. I couldn't handle the itching anymore. For me, I actually have some random things that can trigger hives. There's a certain german suntan lotion that does it, I think the ivy scrub or benedryl cream i was using triggered them this time. My sisters bf breaks out in hives when they drive through a busy city - just from stress.