What would cause hives that come and go throughout the day, appearing symmetrically? ex. ears then subside; armpits then subside; inner thighs, etc.

See a dermatologist: Begin with a diagnosis. If hives, is it physical (dermographism) or allergic or other. How long? If hives daily for more than 6 weeks, likely chronic urticaria, which is not an allergy. Benadryl (diphenhydramine) is a poor choice because it is more of a sleeping pill which should never be used if you drive or work. Zyrtec (generic ceterizine) is more effective and much safer. You can also try 1 or 2 claratin.