insomnia
"Unlike many folks on this thread, I take the highest recommended dose.  If I do not, I will not stay asleep.  I have never had problems falling asleep - but staying asleep.  I would wake up 3 hours after falling asleep and be up the rest of the night.  I was taking SIX Benadryl per night to fall asleep, and my husband finally made me go to the doctor.  He started me on 100mg and told me to go up to 400mg (the highest recommended dose) depending on how I slept.  I now sleep like the dead - I fall asleep easily, and stay asleep until my alarm goes off - waking up completely refreshed.  I cannot imagine trying to sleep without this medicine."