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Allergies, insect bites, and mild anxiety can make dogs uncomfortable, leaving many pet parents wondering if Benadryl is a safe option. Benadryl for dogs is commonly recommended by veterinarians to help relieve itching, swelling, and allergic reactions when used correctly. Understanding proper Benadryl dosage for dogs, possible side effects, and safety considerations is essential before giving any medication. This guide covers the most important things dog owners should know to use Benadryl responsibly.
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.
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, helps 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 your dog needs if he/she believes it is necessary.
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 |
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
1. How Many 25 mg Benadryl Can I Give My Dog?
A dog should receive 1 mg of Benadryl per pound of body weight for each dose. This means a 25-pound dog could safely take 25 mg of Benadryl two to three times per day, as long as your veterinarian approves.
2. Can I Use Human Benadryl for My Dog?
Yes, human Benadryl is generally safe for dogs and cats. However, you should never give your dog a new medication without consulting your veterinarian first to ensure it is appropriate and safe.
3. Can Too Much Benadryl Hurt a Dog?
Yes, too much Benadryl can be harmful to dogs. Overdosing may cause symptoms such as excessive drowsiness, increased heart rate, drooling, or digestive upset. If your dog ingests too much Benadryl, contact your veterinarian immediately.
4. Can I Give My Dog 20 mg of Benadryl?
Yes, if your dog weighs 20 pounds or more, it can safely take 20 mg of Benadryl. The standard dosage guideline is 1 mg per pound of body weight per dose.
5. How Fast Does Benadryl Work on Dogs?
Benadryl typically begins working in dogs within about 30 minutes. If you do not notice any improvement, consult your veterinarian before adjusting the dosage.
6. Is Dog Benadryl the Same as Human Benadryl?
Dog and human Benadryl contain the same active ingredient, diphenhydramine. In most cases, the medication itself is the same, but dosing and added ingredients should always be checked.
7. What Is Generic Benadryl for Dogs?
The generic name for Benadryl used in dogs is diphenhydramine. This is the same active ingredient found in human Benadryl products.
8. Can a 20 Pound Dog Have 25 mg of Benadryl?
A 25 mg dose is slightly higher than the recommended amount for a 20-pound dog. While some dogs may tolerate this dose, it is best to consult your veterinarian before giving more than the standard guideline.
9. How Long Does 25 mg of Benadryl Last in Dogs?
If 25 mg is an appropriate dose for your dog, the effects of Benadryl typically last between 8 and 12 hours.
Helping Your Dog Stay Safe and Comfortable
Benadryl can be a helpful option for managing mild allergic reactions, motion sickness, and temporary discomfort in dogs when used with care. Knowing the correct dosage, watching for side effects, and understanding when Benadryl may not be appropriate can help protect your dog’s health. Every dog responds differently, so professional guidance is always important. By working closely with your veterinarian, you can make informed decisions that support your dog’s comfort and overall well-being.
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