Diphenhydramine is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms. Diphenhydramine is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson's disease. Diphenhydramine is a prescription medication used to treat the symptoms of an allergic reaction, insomnia, cough, motion sickness, and parkinsonism. Learn about side effects, dosages, drug interactions, warnings, and more. 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 Find out how diphenhydramine treats symptoms of allergies and short-term insomnia, and how to take it. NHS medicines information on diphenhydramine – what it's used for, side effects, dosage and who can take or use it. Learn about diphenhydramine usage and dosing. Read the latest news and reviews about the drug as well as potential side effects and popular alternatives. Diphenhydramine, or Diphenylhydramine, sold under the brand name Benadryl among others, is an antihistamine and sedative. Although generally considered sedating, diphenhydramine can cause paradoxical central nervous system stimulation in some individuals, particularly at higher doses. Diphenhydramine is in a class of medications called antihistamines. It works by blocking the action of histamine, a substance in the body that causes allergic symptoms. Diphenhydramine is a first-generation antihistamine used for symptoms of allergies and colds, such as sneezing, runny nose, or skin rash. It is also used to induce sleep, motion sickness, and some symptoms of Parkinson's disease. Diphenhydramine Hydrochloride is the hydrochloride salt form of diphenhydramine, an ethanolamine and first-generation histamine antagonist with anti-allergic activity. Allergy (Diphenhydramine HCl) is an antihistamine that is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms. Allergy (Diphenhydramine HCl) is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson's disease.