Giving your dog Benadryl can help relieve a number of symptoms, but always check with your veterinarian before administering it. Remember: Benadryl is the brand name and not the name of the drug that produces the effects. Make sure the formulation you choose contains diphenhydramine as the only active ingredient before giving it to your pet. The main ingredients are usually displayed clearly on the front and back of the box. Dr. DuBose recommends giving a dose every 8 to 12 hours.