Benadryl is a brand name for a number of different medications. In the United States and Canada, it contains the antihistamine diphenhydramine. In the United Kingdom, it contains either the antihistamine acrivastine (marketed as Benadryl Allergy Relief) or the long acting antihistamine cetirizine (marketed as Benadryl One a Day Relief). Benadryl products are marketed in Australia and New Zealand as a cough medicine and do not contain any antihistamine.