Benadryl is one of many antihistamines. It is used mainly to control the symptoms of allergies and hay fever. What this drug does is to block the natural occurring chemical histamine that is in the human body. This natural histamine is what is known for causing various allergy symptoms. It comes available in both oral and topical forms. Benadryl was a drug that was first synthesized by a man named George Rieveschi and it was made available for prescription for the very first time, for the public, back in 1946.