Can I Give My Dog Benadryl?

Yes, with care
Diphenhydramine is commonly referenced for dogs at published doses. The published veterinary reference range for diphenhydramine in dogs is 2-4 mg per kg of body weight, given every 8-12h. In practice: 1 mg per lb (2.2 mg/kg). Plain diphenhydramine ONLY, combination products (with decongestants or acetaminophen) are dangerous. Drowsiness expected.
Source: Merck Veterinary Manual
Get the exact range for your dog's weight

Skip it or ask a vet first if

glaucomaurinary obstructionwith sedativescombination cold products

Published range by weight

WeightDiphenhydramine (published range)
10 lb dog9.1-18 mg
25 lb dog23-45 mg
50 lb dog45-91 mg
75 lb dog68-136 mg

Computed from the published 2-4 mg/kg reference range, every 8-12h. Product strengths rarely split evenly, so round DOWN to the nearest practical dose and confirm with your vet.

Cats use a different amount

The published cat reference (2-4 mg total per cat) differs from the dog range. Never split the difference between species; check the cat page instead.

About Diphenhydramine

Diphenhydramine is an antihistamine, a class used to blunt allergic responses like itching, hives, and insect-sting swelling. You will see it sold as Benadryl, and the label strength on the box is what matters for the math, not the brand. Reference data on this page reflects published veterinary sources, not a prescription for your dog.

What to have ready when you call the vet

Whether you are confirming a dose or reporting that your dog already got into something, the call goes faster with four facts ready: your dog's current weight, the exact product name and strength from the label, how much was given or eaten, and roughly when. With those, most clinics can answer in one call.

The safe habit

Confirm any medication decision with your veterinarian, who knows your dog's health history and other medications. VetDose shows published reference data, not prescriptions.

See also

Other antihistamine questions for dogs