What is Diphenhydramine HCl? Diphenhydramine HCl is an antihistamine that’s commonly used to relieve allergy symptoms like sneezing and itching. It’s also widely used as a sleep aid because it causes drowsiness, which can help people fall asleep faster. How does it help you sleep? Diphenhydramine blocks histamine receptors in the brain. Histamine is involved […]






