Benadryl for Dogs: Uses, Safety, Side Effects and How Long It Takes to Work
Benadryl (diphenhydramine) is an antihistamine that veterinarians sometimes recommend for dogs with mild allergic reactions, itching, insect stings or motion sickness. It usually starts working within about 30 minutes to an hour, and the effects last several hours. It isn't safe for every dog, though, and the right dose depends on your dog's weight and health, so call your vet before you give it.
Giving Benadryl to your dog: should you do it? Is it helpful and harmless, or a bad idea? Below we cover what Benadryl does, when vets use it, who shouldn't take it, how fast it works and the side effects to watch for.
What Is Benadryl?
Benadryl is a common over-the-counter antihistamine that you can buy at any drug store, pharmacy, or grocery store.
Like other antihistamines, its primary use is to help reduce symptoms associated with allergies, such as itching, hives, sneezing and runny nose. It also causes drowsiness, which is why it's sold as a sleep aid for people.
Keep in mind that Benadryl is the brand name for the active ingredient called diphenhydramine. Many store brands use the same active ingredient. But store shelves also carry "Benadryl" products with different or extra ingredients, so always read the "Drug Facts" label. More on that below.
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Benadryl for Dogs Uses
Veterinarians may recommend diphenhydramine for dogs in situations like these:
- Mild allergic reactions, such as hives or itchy, irritated skin
- Insect or flea bites and bee stings, when the swelling is mild
- Seasonal or environmental allergies
- Car sickness and motion sickness
- Mild sedation for travel, or before a stressful event
- Before or after certain treatments, when your vet advises it, for example if your dog has had a mild reaction to vaccines in the past
What Benadryl is not: it isn't a treatment for a severe allergic reaction. If your dog's face is swelling quickly, they're struggling to breathe, vomiting repeatedly or collapsing, go to an emergency vet right away. And while it can make a dog sleepy, it's not a long-term answer for anxiety, storm fear or separation anxiety. Your vet has better options for those.
Can I Give My Dog Benadryl? Is Benadryl Safe for Dogs?
Many healthy adult dogs can take diphenhydramine safely when a vet recommends it and sets the dose. But it is a drug, and it isn't right for every dog. Check these points with your vet first:
Puppies, seniors, and pregnant or nursing dogs. Ask your vet before giving any medication. Young puppies are small and their bodies handle drugs differently.
Avoid combination cold, sinus and "PM" products. Many products sold under the Benadryl name or as store brands add decongestants (such as pseudoephedrine or phenylephrine), pain relievers (such as acetaminophen) or other drugs that can be dangerous or deadly for dogs. Diphenhydramine should be the ONLY active ingredient on the label.
Check liquids and chewables for xylitol and alcohol. Some liquid and chewable formulas contain xylitol, a sweetener that is toxic to dogs, and some liquids contain alcohol. Read the inactive ingredients and ask your vet or pharmacist if you're unsure.
Some health conditions don't mix with antihistamines. If your dog has glaucoma, heart disease, high blood pressure, seizures, prostate or urinary problems, or thyroid disease, your vet needs to decide whether Benadryl is safe.
Other medications. Diphenhydramine can interact with sedatives, some anxiety and pain medications and other drugs. Tell your vet everything your dog takes.
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How Much Benadryl Can I Give My Dog?
The amount of Benadryl your dog needs depends on its weight, its health, the reason you're giving it and any other medications it takes. That's why we don't publish a dosing chart. Call your veterinarian for a dose before you give your dog Benadryl, even if you've given it before.
A few practical points when you talk to your vet:
- Have your dog's current weight ready. Many smaller dogs need much less than a standard human tablet, so your vet may suggest a different strength or form.
- Ask how often it can be repeated and the maximum in a day.
- Bring or photograph the exact product so your vet can check the strength and the inactive ingredients.
How Long Does Benadryl Take to Work in Dogs?
Benadryl absorbs quickly. Most dogs start to show effects within about 30 minutes to an hour, often as drowsiness first, with itch or hives easing over the next hour or two. The effects typically last several hours.
If you don't see improvement in a mild reaction within an hour or two, or symptoms get worse at any point, call your vet instead of giving more. Swelling of the face or throat, trouble breathing, or collapse are emergencies.
Side Effects of Benadryl
The most commonly reported side effect is drowsiness. Some dogs have the opposite reaction and become restless or excited.
Other side effects include:
- Dry mouth
- Mild disorientation or wobbliness
- Diarrhea
- Lack of appetite
- Vomiting
- Agitation
- Rapid heartbeat or rapid breathing
- Urinary retention (not peeing)
If you think your dog is experiencing any of these side effects, give your vet a call. If your dog may have taken too much, or got into a product with other ingredients, signs can include severe agitation, a racing heart, dilated pupils, tremors, seizures or extreme sleepiness. Contact your vet, an emergency clinic or the ASPCA Animal Poison Control Center right away.
Tips for Giving Benadryl to Your Dog
Get your vet's go-ahead first. Ask about the dose, the product and how to watch for side effects.
Watch the first time. Stay with your dog for a few hours after the first dose and note how they react.
Give it with food. Giving the tablet with a meal or a tasty treat can help with stomach upset. A food your dog is excited about, like Bully Max high-protein dog food, makes this easy.
Hide the pill in something soft. Most dogs are less than eager to swallow a whole pill. Tuck the tablet into a small piece of meat or a soft treat and most dogs will wolf it down. Only split tablets if your vet tells you to.
Skip gel caps unless your vet says otherwise. Breaking open gel caps makes it hard to know how much your dog actually got.
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Frequently Asked Questions
How long does Benadryl take to work in dogs?
Usually about 30 minutes to an hour. Drowsiness often shows first, and the effects last several hours.
Can dogs take Benadryl?
Many dogs can, when a veterinarian recommends it and sets the dose. Use a product with diphenhydramine as the only active ingredient and no xylitol, and check with your vet first if your dog is a puppy, pregnant, on other medications or has a health condition.
Does Benadryl help dogs with itching?
It can help some mild, allergy-related itching and hives, but it often isn't enough for ongoing skin problems. If your dog itches for more than a few days, see your vet to find the cause, such as fleas, food or environmental allergies or infection. If food turns out to be the trigger, our guide to dog food for allergies explains options with limited protein sources.
Can I give my dog Benadryl for anxiety or storms?
It may make some dogs sleepy, but it doesn't treat fear itself and some dogs get more restless. Ask your vet about better options, and see our tips on how to calm a dog during a storm.
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117 comments
Hi guys, I have an Aussie bulldog (sorry not a pit bull) but he is terrified in storms, so much that no matter where he is, he escapes and runs away. Due to current circumstances I am unable to have him inside in a storm, especially when they hit during the day.. what is recommend to knock him out enough so that he doesn’t climb out of his enclosure?
I have a Chihuahua mix and last time he was weighed he was 15 pounds but I believe he is not about 20 pounds. I have been giving him half a tablet of 25mg. At first every 24 hours and now at the moment every 12 hours. He has bad environment allergies.
Do you think I can give him an entire tablet of Benadryl every 24 hours?
Or should I just give him half the tablet every 8 hours? Though it’s not easy as I’m away from home 7am to 5:30pm. But I can start I can give it to him tonight and then have someone give it to him on Friday when I’m not home. And then I’ll be home Saturday and Sunday.
I plan on starting him on fish oil. And I am currently spraying spraying him with a dog itch relief tea tree. And will buy him GNC itch relief shampoo.
Gave our 4yr old 17lb yorkie bath with medicated shampoo (we never use this ) she broke out in hives pea and dime size…we have given about 5ml of children’s liquid …they haven’t gotten worse but haven’t gotten better either …any suggestions? ??
For those that are giving their pets Benadryl on a regular basis because of skin allergies or something of the sort, I would recommend trying to find thine source of the allergy, dryness, irritation, or whatever and treating that. Speaking from personal experience, I because allergic to antihistamine from taking it so much because of allergies. I still have allergies but now can’t take antihistamine so I have learned to find and eliminate causes as much as possible or find more natural ways to treat the symptoms. I’m not saying not to use this, but maybe sparingly is better. I’m not a vet though. Just someone with personal experience. I have been able to change the condition of my pets’ skin by changing what they eat and what I bath them with.
The recommended dosage makes no sense at all. If this theory was applied to humans, a two hundred pound man would take 200mg of Benadryl. It’s strange to see such advice given by professionals. Dogs 20 pounds and under should get a children benadryl at 12.5 mg. Dogs 20 – 40 pounds should get a 25 mg dosage and dogs 40 pounds and above should get 25-50 mg dosage dependent upon ailment. Most people are absent of the fact that 50 mg of Benadryl is actually used as a sleeping aid for humans. I can’t imagine any dog ever needing more than 50 mg of benadryl at one time.