What’s the active ingredient in the USA?
Over here it varies:
In the United Kingdom, Benadryl products contain either the second-generation non-sedating antihistamine acrivastine (marketed as Benadryl Allergy Relief, with a suggested efficacy duration of eight hours) or the non-sedating antihistamine cetirizine (marketed as Benadryl One a Day Relief). Cetirizine is indicated for the relief of symptoms associated with allergy and hives. It is an orally active and selective H1 receptor antagonist.