Benadryl or Generic Diphenhydramine (die-fen-HIDE-ra-meen) is an antihistamine, used to relieve or prevent the symptoms of hay fever and other types of allergies. They work by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. Diphenhydramine can cause significant drowsiness, and reduce your ability to concentrate and learn.
Last Updated: 12/17/08