Looks like I've got one who gets hyper on Benadryl.

It's not that I want her groggy either, but WOW does she get crazy!

She still has a head-to-toe rash without the Benadryl, and it DOES respond to the medication, so I am more certain than I was before (which was really certain) that it's "just" hives.

I will no longer hesitate to give her the Benadryl during the times she's supposed to be awake, though - I'd been holding off until nap and bedtime, which has made those times raaaather interesting. Now I will consider holding off at bedtime, and checking her regularly at night.