I got hives in my last year of archictecture school so I understand the stress hive concept. And, yes, I'd suggest keeping benadryl on hand for awhile - you might want to take a low dose for a few days before you go to bed (cause benadryl makes me sleepy), to try and knock down the build-up of histamine in you system.

Also, get some simple, fragrance free soaps (incl. laundry soap).

The think with the recurrance is that, even if it's stress, it's building up histamine in you system and you'll get sensatized until those levels go down. Oral beandryl will help with that.