If you were going to have an allergic reaction to Klonopin it wouldn't have taken a year to manifest, plus as you're aware there would be other symptoms. Histamine reactions to stress are very common and often show as skin breakouts. It is no coincidence than most antidepressants are also powerful antihistamines. An over-the-counter antihistamine like Benadryl should help, both in controlling the hives, and also hopefully easing your mind. Just be aware that they can be sedating.