Benadryl Allergy is the name of a Benadryl product found in the United States and Canada. It is an antihistamine drug used to relieve allergies. Its active ingredient is diphenhydramine, a first-generation antihistamine. It is known to be sedative, making drowsiness a common side effect. It is an oral drug to be taken by mouth, to relieve symptoms of allergy, hay fever and the common cold. [1. Giving your child Benadryl? Find the recommended amount of Benadryl to give your child based on age and weight using the St. Louis Children's Hospital Benadryl dosage chart. Detailed Diphenhydramine dosage information for adults and children. Includes dosages for Insomnia, Allergic Rhinitis, Allergic Reaction and more; plus renal, liver and dialysis adjustments. Benadryl is a brand) name for diphenhydramine hydrochloride, a sedating antihistamine used to treat allergies, sleep problems, and motion sickness. The recommended dosage of Benadryl by condition is as follows. Benadryl (diphenhydramine) is an over-the-counter (OTC) antihistamine used to treat allergy symptoms, such as sneezing and runny nose. It’s safe for most adults and children ages 6 and older to take at recommended dosages. The typical adult Benadryl dosage is 1 to 2 tablets or capsules by mouth every 4 to 6 hours as needed. Adults ages 65 and older should contact a healthcare professional. Home › Health › Benadryl Dosage Calculator Benadryl Dosage Calculator Calculate the appropriate diphenhydramine (Benadryl®) dose based on body weight, age, and formulation. This tool supports liquid, chewable, tablet, and capsule forms for both children and adults. Get the facts on Benadryl’s dosages. You can also learn how to take the drug, which forms it comes in, and more. Benadryl (diphenhydramine) is a brand-name over-the-counter drug that’s used for allergies and itchy skin. Learn about side effects, price, and more. Find out how much Benadryl adults and children can safely take, plus essential safety tips and side effects to watch for in this medically-reviewed guide. Find BENADRYL® dosage information for adults, children, and toddlers and learn how much you and your family should take with our allergy medicine product-dosing guide.