The Benadryl dosage for dogs calculator is the simplest way to calculate a safe dose of Benadryl (Diphenhydramine) for your beloved dog. No matter what you need it for - allergy, motion sickness, or anxiety - we've got you covered. We'll tell you everything you need to know about giving dogs Benadryl, a choice of different allergy medicine for dogs available on the market, and possible side effects of antihistamine for dogs.