Introduction Diphenhydramine, widely known by its brand name Benadryl, is a first-generation antihistamine commonly used to treat allergies, hay fever, colds, and insomnia. Over the years, it has earned a reputation as a go-to medication for its sedative properties and easy over-the-counter access. However, recent studies and medical warnings have brought to light the dark side of long-term diphenhydramine use, especially its impact on cognitive health and brain function. While effective for short-term relief, regular or long-term use—particularly for sleep—can pose significant neurological and psychological risks, including memory loss, confusion, and increased risk of dementia. The concern stems from diphenhydramine’s…