Shelter Dog Meal Donation Count:

Learn More

Benadryl Dosage For Dogs: 5 Things Dog Owners Should Know

| Published on January 1, 2024

Reviewed by: Dr. Theresa Fossum

Reviewed by:

Dr. Theresa Fossum

Meet Dr. Theresa (Terry) W. Fossum, DVM, MS. Ph.D., Diplomate ACVS – a remarkable animal lover whose passion for animal care and innovative solutions has left an indelible mark on the veterinary world. As the CEO of both Phoenix Animal Wellness and Epic Veterinary Specialists, she's ensuring dogs and cats receive the highest level of care and compassion.Read more
Can You Give A Dog Benadryl?

Caring dog owners are always super cautious about what they let their dogs ingest, from the food they eat to the medicines they take. While you should never give your pup medication without advice from your vet, there are a few over-the-counter drugs for humans your canine may benefit from in certain instances. If you are looking for the correct dosage of Benadryl to give your dog, we found a great infographic from Dog Health Coach.

Benadryl for Dogs


Do I Need to Buy a Benadryl Product Made Specifically for Dogs?

Oftentimes, human medications contain additives such as artificial sweeteners and coloring that are not healthy and even deadly to dogs. Always check the label and talk with your vet when in doubt. You can also purchase a Benadryl made specifically for dogs (like this one available on Amazon):

Does Benadryl Make Dogs Sleepy?

You may have heard of pooch parents giving their dogs Benadryl for seasonal allergies, or even to make them drowsy and stave off nausea on the occasional car ride. The most common question we get “is it safe, and how will it affect my dog when I give them Benadryl?”.

We here at iHeartDogs got in touch with Dr. Michel Selmer, DVM, CTCVMP, to answer some questions for us. Also known as “The Caring Vet,” he offers traditional, holistic, integrative medical, surgical, and wellness care to his patients.

Again, you should always consult with your vet before administering any type of medication to your dog. Read the interview below to help you decide if an antihistamine is something your dog may benefit from.

iHeartDogs: What is Benadryl Used to Treat in Dogs?

Dr. Selmer: Benadryl is an antihistamine used primarily for the prevention of motion sickness, as a sedative, for anti-nausea and for itchiness as a result of an allergic reaction (dogs with mast cell tumors, etc.). Benadryl inhibits histamine release, can cause sedation, help dry up mucus membranes, inhibits coughing, and controls nausea.

iHeartDogs: Can I give my dog Benadryl every day? Any particular instances/conditions that make it unsafe?

Dr. Selmer: Generally speaking, Benadryl is safe… Benadryl would be contraindicated in dogs that have had an adverse side effect to Benadryl or any other antihistamine. It should also be used cautiously in dogs with glaucoma, difficulty urinating due to an enlarged prostate or obstructions at the neck of the bladder, vomiting due to an obstruction at the pylorus (between the stomach and duodenum), hyperthyroid disease, cardiovascular disease and/or high blood pressure (hypertension).

iHeartDogs: How much Benadryl should I give my dog?

Dr. Selmer: Your veterinarian will advise you on the dose of Benadryl if he/she believes your dog needs it.

Benadryl For Dogs: How Much Benadryl Can I Give My Dog?

(Note from iHD: New York State Law prohibits vets from diagnosing or prescribing meds to non-clients, so Dr. Selmer cannot give Benadryl dosing information in this post.)

However, for a general idea, WebMD advises:

“The standard dosage for oral Benadryl is 1 mg per pound of body weight, given 2-3 times a day. Most drug store diphenhydramine tablets are 25 mg, which is the size used for a 25 pound dog. Always double check the dosage before giving an over the counter medication.”

Dog’s Weight Benadryl Dosage in mg Benadryl Dosage in mL
10 lbs 10 mg 0.01 mL
20 lbs 20 mg 0.02 mL
30 lbs 30 mg 0.03 mL
40 lbs 40 mg 0.04 mL
50 lbs 50 mg 0.05 mL
60 lbs 60 mg 0.06 mL
70 lbs 70 mg 0.07 mL
80 lbs 80 mg 0.08 mL
90 lbs 90 mg 0.09 mL
100 lbs 100 mg 0.1 mL
110 lbs 110 mg 0.11 mL
120 lbs 120 mg 0.12 mL
130 lbs 130 mg 0.13 mL
140 lbs 140 mg 0.14 mL
150 lbs 150 mg 0.15 mL
160 lbs 160 mg 0.16 mL
170 lbs 170 mg 0.17 mL
180 lbs 180 mg 0.18 mL
190 lbs 190 mg 0.19 mL
200 lbs 200 mg 0.2 mL

Dog with Benadryl tablets

iHeartDogs: How long will Benadryl affect my dog?

Dr. Selmer: In dogs, the effects of Benadryl usually last 8 – 12 hours.

iHeartDogs: How will my dog act while under the effects of Benadryl?

Dr. Selmer: The most common side effects of Benadryl are lethargy, dry mouth and urine retention. Diarrhea, vomiting and decreased appetite are possible, but not common. There is no evidence that Benadryl will cause fear in dogs. Interestingly enough, there is evidence of excitement as a side effect in some cats.

A Side Note From Dr. Selmer:
Most people think to use Benadryl when their dog is having an allergic reaction. Benadryl will work best when given very early in the event of an allergic reaction before histamine is released. Once a dog is symptomatic the histamine has already been released and Benadryl may not help.

Benadryl, or any other antihistamine, is best used in dogs with a predictable pattern of allergic exposure. For example, I will typically recommend an antihistamine (ie. Zyrtec, Benadryl, Atarax or Chlor-Trimeton) before the start of allergy season in a dog with seasonal allergies and to continue until allergy season is over.

I have not found antihistamines to be very good at controlling the itchy dog, as there are many things that can cause a dog to be itchy and histamine release is only one pathway. So, if Benadryl doesn’t work for an itchy dog after using it for 14 days I would recommend trying a different antihistamine.

More Frequently Asked Questions

How Many 25 mg Benadryl Can I Give My Dog?

A dog should get 1 mg of Benadryl per one pound of body weight for each dose. So, a 25-pound dog could take 25 mg of Benadryl 2 to 3 times per day.

Can I Use Human Benadryl for My Dog?

Yes, human Benadryl is safe for dogs and cats. However, you should never give your dog new medications without talking to your vet first.

Can Too Much Benadryl Hurt a Dog?

Yes, too much of any medication could have a negative impact on your furry friend. Dogs may experience symptoms like drowsiness, increase heart rate, drooling, or digestive issues. If your dog consumes too much Benadryl, take them to the vet right away

Can I Give My Dog 20 mg of Benadryl?

Yes, if your dog is 20 pounds or larger, it can safely ingest 20 mg of Benadryl. A proper dose is 1 mg per pound of body weight.

How Fast Does Benadryl Work on Dogs?

It usually takes about a half hour for Benadryl to work on dogs. If nothing happens, talk to your vet about potentially changing the dosage.

Is Dog Benadryl the Same as Human Benadryl?

Dog and human Benadryl use the same active ingredient: diphenhydramine. So, in most cases, the medication is the same for dogs and humans.

What is Generic Benadryl for Dogs?

The generic name for dog Benadryl is diphenhydramine. It’s the same active ingredient as in human Benadryl.

Can a 20 Pound Dog Have 25 mg of Benadryl?

25 mg is slightly above the recommended dose for a 20-pound dog. Some 20-pound dogs may do fine with that dosage, but you should ask your vet before giving your dog a higher-than-recommended dose.

How Long Does 25 mg of Benadryl Last in Dogs?

If 25 mg is the correct dose for your dog, the effects will last for 8 to 12 hours.

Benadryl Dosage For Dogs: 5 Things Dog Owners Should Know

Can You Give A Dog Benadryl?

Recent Articles

Interested in learning even more about all things dogs? Get your paws on more great content from iHeartDogs!

Read the Blog