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. Diphenhydramine, also known by the brand name Benadryl, is an over-the-counter antihistamine used to relieve allergy or common cold symptoms in adults and children. 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. Benadryl is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose. Benadryl is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms. 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. Benadryl can cause drowsiness and should not be used when driving. Taking large doses of Benadryl can lead to serious health issues like cardiac arrest and death. People with glaucoma should talk to a doctor before using Benadryl because it can cause vision problems. Shop items from Benadryl at Walmart.com and learn more about how you can save money on the best Benadryl products to help you live better. 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 a brand of various antihistamine medications used to treat allergies, whose content varies in different countries, but which includes some combination of diphenhydramine, acrivastine, or cetirizine. 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.