Benadryl (diphenhydramine) is a brand-name over-the-counter drug that’s used for allergies and itchy skin. Learn about side effects, price, and more. Benadryl® (diphenhydramine) is a liquid medication that treats the symptoms of allergies and allergic reactions. It may also prevent and treat motion sickness or the symptoms of Parkinson’s disease. What is Benadryl (diphenhydramine)? Benadryl is a brand) name for diphenhydramine hydrochloride, a sedating antihistamine used to treat allergies, sleep problems, and motion sickness. Find yourself needing help relieving allergies or a pesky itch? Check out the many allergy and itch relief products from BENADRYL® that may provide relief. Benadryl is a brand of antihistamine medications used to treat allergies, whose content varies in different countries, but which may include diphenhydramine, acrivastine, or cetirizine. Do you need help relieving allergies or a pesky itch? Check out the many allergy and itch relief products BENADRYL® offers which may help provide relief. Find patient medical information for Diphenhydramine (Benadryl, Unisom, and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings Benadryl (diphenhydramine) is an antihistamine used to treat allergies, hives, insomnia, motion sickness, and mild cases of Parkinsonism. Benadryl is available in generic form and over-the-counter (OTC). Benadryl is an antihistamine and is used to treat sneezing, runny nose, itching and other allergies. Learn about side effects, interactions and indications. Find BENADRYL® dosage information for adults, children, and toddlers and learn how much you and your family should take with our allergy medicine product-dosing guide.