Question: how many mg of antihistamine can you give a dog?
Answer: Most drugstore diphenhydramine tablets, whether generic or brand name Benadryl, are 25 milligrams. The standard dosage for a dog is 1 milligram per pound of body weight, so one tablet is perfect for a 25-pound dog. Veterinarians suggest giving a dose every 8-12 hours (about 2-3 times a day).