What is the limit of Benadryl (diphenhydramine) allergy pills you should take as an adult?

1-2 every 4-6 hrs. Benadryl (diphenhydramine) is an antihistamine used in the treatment of allergies. It doesn't work long so it has to be taken often. The recommended dose is 1 or 2 pills (each 25 mg) every 4-6 hours, so a maximum of 12 per day (300 mg/day). Taking any Benadryl can cause sleepiness, headaches, dry mouth, & difficulty urinating. Excess Benadryl can cause delirium, diarrhea, seizures, and even coma.
Depends. Follow the directions on the bottle unless you have spoken with your physician who gave you a different instruction list. The maximum recommended daily dose (not all at once) is 300mg/day.