Benadryl is an over-the-counter antihistamine medication that stops the effects of histamines, which are chemicals that are naturally found in the body. Benadryl is available in capsule, powder, liquid, dissolving strip, and tablet forms. Benadryl, also known by the generic name diphenhydramine, is used to treat a number of symptoms and conditions. Benadryl is often used to manage allergies and control symptoms such as skin rash and hives, eyes that itch and water, sneezing, and runny nose. Benadryl can also ease symptoms of the common cold, help control a cough, and also manage motion sickness. Benadryl is known to induce drowsiness, and may sometimes be used to treat mild symptoms of Parkinson's disease.