I took 4 tablets of benadryl (diphenhydramine) and i'm 16 years old can that harm me? and what will happen if i take 5 ?

Why four?: Four benadryl (diphenhydramine) tablets is a lot. They can make you very sleepy and cause you to have a racing heart, dry mouth, difficulty urinating and other symptoms. Don't take a fifth. The real question is why are you taking them? If you're trying to hurt yourself, please tell a family member and go to the ER to be evaluated and talk to someone! If it's just to rest, you've had more than enough.