Diphenhydramine can be harmful if people take it after having an allergic reaction to food, she said, because the drug – best known by the brand name Benadryl – makes them drowsy and can cause. 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. But as newer antihistamines have become available over the past two decades, first-generation medications like Benadryl are no longer recommended for regular allergy treatment. AAAAI's Ask the Expert talks about an allergic reaction to diphenhydramine. Benadryl Allergy is an antihistamine that is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms. Benadryl Allergy is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson's disease. Benadryl treats allergy symptoms like sneezing, runny nose, and itchy skin. It is also used short-term as a sedating antihistamine—not as a long-term sleep plan. 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. Use BENADRYL ® Allergy ULTRATABS ® Tablets with 25 mg of diphenhydramine HCI, which are antihistamine allergy tablets, for effective relief from both indoor and outdoor allergies. Benadryl is an antihistamine and is used to treat sneezing, runny nose, itching and other allergies. Learn about side effects, interactions and indications. Benadryl products that are taken by mouth are used to treat allergy symptoms such as sneezing, itchy/watery eyes, runny nose, and itchy nose and throat. Some Benadryl products may also.