Benadryl is a brand name for a number of different antihistamine medications used to treat allergies and symptoms including itching, watery eyes, runny nose, and sneezing. Diphenhydramine also can cause drowsiness and cause people to fall asleep. The product is not recommended for use to make a child sleep. In the United States and Canada, it is the first-generation antihistamine diphenhydramine. In the United Kingdom, the active component of is often the antihistamine acrivastine, or cetirizine. Some products marketed in Australia and New Zealand as a cough medicine with the Benadryl name contain diphenhydramine.