1.) When used for its intended purpose, it is very useful for the treatment of allergies.
2.) When used at doses 4 or more times the recommended dose, it is a hallucinogenic deliriant. If you manage to fight off the extreme drowsiness and stay awake, it could hardly be considered an escape from reality, as the hallucinations experienced usually very closely resemble reality. For example, you'll quite likely see one of your family members and upon trying to interact with them, they'll disappear. This is more freightening than it may sound, as some of these encounters may be not-so-friendly, such as thinking you're getting busted by your parents for attempting to bake a cake in your dresser drawer. It is damn near impossible to differenciate between hallucinations and reality. Also, you'll more than freak out anyone around you who doesn't know you've taken something. There's a 99.9% percent chance that you'll respond to questions you were never asked or try to make comments on events you thought you saw, only to scare the piss out of them. Hardly worth it.
Oh shit, I wonder how much damage I caused on that benadryl trip last night.