Can My Dog Take Benadryl?

For some pet parents, the idea of a home remedy or “DIY” approach to their dog’s illness can be alluring. It skips the often-expensive vet bills, allows immediate treatment, and in some cases, doesn’t even call for a trip to the store – but is it safe? 

With a wealth of old wives’ tales and nearly endless opinions on pet care online, even the answers to a simple question like “Can my dog take Benadryl?” will be murky at best. Here’s how to find the right solution to not only help an ailing canine’s symptoms, but to ensure his ongoing health as well.

Human Medication versus Dog Medication

It’s no secret that human and canine anatomy looks very different. However, despite sharing the same general organs, these similarities do not necessarily translate to the same metabolism and body processes. Dogs, for example, are built for running on all fours and have more sensitive lungs than their human counterparts. Humans, on the other hand, are able to more efficiently shed heat in the form of sweat across their (comparatively) hairless skin. These changes affect the way that medicine is processed throughout the body, and what works well for one could very well be harmful – or even deadly – for the other.

Just as humans avoid taking medication prescribed to someone else, dogs should never be given medication they have not been prescribed by a vet – even canine medications. A veterinarian considers a wide variety of factors when prescribing medicine, including breed, age, general health, temperament, and weight. Without this information and a professional medical “green light,” a dog could very easily be given a dose that is far too potent for his size, leading to liver or kidney damage. No matter how well-meaning his pet parent’s actions may be, an accident like that could have serious and lifelong consequences for his health.  

Is Benadryl Safe For Dogs?    

Everything from the food humans eat to the paint they use to decorate their house is subject to regulation: these products are tested and held to a certain standard in order to be sold. Medication in particular is very carefully tested and examined, and used for a specific purpose: it can’t be officially recommended by the FDA to treat other ailments, even if it’s found to work for them. Benadryl use in dogs is one of these medical scenarios: the medicine is cleared and recommended to work on humans, but is not officially recommended for or tested on dogs. This doesn’t mean it’s never used, and in fact many vets can and do prescribe it – only that the FDA isn’t able to approve that use. 

The long answer to the question of safety is it depends. If a vet examines a dog, determines he could benefit from Benadryl, prescribes a dosage, and the dog’s pet parent administers it properly, it becomes a tentative yes. If the dog has successfully taken Benadryl previously and has had no other serious health concerns crop up in the interim that “yes” gets a lot stronger.

If, on the other hand, that same pet parent takes matters into their own hands, does some cursory internet research, and simply starts giving their dog Benadryl. That pushes the answer further into the “no” column, and canine health complications become considerably more likely. The risk to the dog increases when the DIY approach is taken over a long stretch of time, or if he’s never taken to a vet to properly diagnose his symptoms. 

The Problem With Word-of-Mouth

Some human medications have a long and storied history of being used on animals – so-and-so’s cousin swears by it, a neighbor’s groomer said it worked, a friend mentioned something they read on the internet. The problem with this kind of advice is that it’s not specific to a dog, and even in the unlikely event each secondhand story is completely true, what works for one pup might not work well for another. 

Dogs, on the whole, tend to be very hearty animals, able to eat food that’s spoiled, or even raw meat with far less risk than humans would endure. That said, for some breeds, a single grape or raisin could cause catastrophic health issues – proof that even an “iron stomach” isn’t an invulnerable shield. If there are underlying canine health issues, or a dog is too small, weak, or ill, the same Benadryl that would have been a big help months ago can become a cause for concern. 

The dogs in word-of-mouth stories are almost always poorly defined – seldom do important details like their breed, age, and health appear alongside the potential cure. Variables like their vaccination schedules and even their home climate can change the efficacy of medicines – dogs, for instance, have seasonal and regional allergies, just like their human companions. A dog in a warm climate with a high pollen count is far more likely to be suffering from allergies –and in need of a medicine like Benadryl – than one in a relatively dry, arid climate without a seasonal bloom. 

Using Benadryl For Dogs

In humans, these little pink pills are generally reserved for preventing serious allergic reactions, such as pollen allergies in the height of the local blooming season. In dogs, however, they’re also used by vets to treat a number of off-label issues, such as canine anxiety or motion sickness during travel. If a pup has canine allergies to certain plants in his yard, or has a problem with constantly scratching due to insect bites, a vet may recommend that he receives Benadryl in a weight-appropriate dosage one to two times a day until symptoms taper off. 

Just as in humans, it’s typically recommended that Benadryl be taken prior to allergen exposure, whenever possible, in order to achieve the best results. Some potential uses for Benadryl in dogs include:

  • To help eliminate motion sickness, typically taken prior to a long car ride or flight. 
  • Used as a sedative or calming medication prior to a stressful event, such as grooming or a medical procedure.
  • Preventatively, to protect against rashes, hives, and itching that come from seasonal or topical allergies from grass, insects, and more.
  • Protectively, to mitigate some of the side effects of certain canine vaccines, or to protect against histamine-based health issues. 

Benadryl Comes In Many Forms

Human medications, particularly over-the-counter varieties, are well-known for having expensive and aggressive marketing strategies. For an instant-relief style of medication like Benadryl, evolving formats are the norm: dissolving tablets, extended release pills, liquid forms, and so on. 

The delivery method of each type brings different ingredients to the proverbial table, and it’s important to bear this in mind. Even if a vet gives the thumbs up for X milligrams of Benadryl for a dog, the vet is usually assuming a hard, classic, tablet-style form of the medication. The liquid form of Benadryl contains alcohol – even if the correct amount of the medication is administered by a pet parent after consulting a vet, the alcohol could severely injure the canine patient. When receiving guidance on using OTC human medications on dogs, always verify the medication format with a vet: this prevents miscommunications like the pill-versus-liquid issue.

Additionally, while some expired medication simply becomes less potent or ineffectual as it ages, other pills and tablets can form harmful substances as they degrade. Expired Benadryl falls into the first category – ineffectual as opposed to dangerous – but it’s important to bear the potential risk of old medication in mind. Err on the side of caution and always give fresh, in-date medication to dogs when recommended by a vet – not expired pills or tablets.  

Advice For Using Benadryl For Dogs

There are a few universal truths when it comes to using this popular antihistamine medication for dogs: namely, don’t do it without a vet’s express recommendation. Every dog is different, and his vet will understand his medical needs the best – not a random internet search or two. 

At the vet’s, always confirm the dosage required, the form of medicine required, and the dosing frequency – e.g. twice a day with meals – before offering a dog Benadryl. Be prepared for potential side effects like nausea or vomiting, as well as lethargy while the medicine works its way through the canine digestive system. 

Finally, never give an unsupervised dog medication for the first time, including Benadryl, without knowing how it will affect him. If, for example, he’s given new medicine just before being closed away in an airplane hold, his pet parents won’t be able to notice and render assistance if side effects occur. When Benadryl is prescribed, ensure that only fresh, in-date medication is used in order to offer consistent and lasting relief to a dog that’s not feeling his best.

Sources Cited:

1)      Burke, Anna. “Benadryl for Dogs.” American Kennel Club (, August 10, 2016, Accessed June 18, 2020.

2)      Vogelsang, Dr. Jessica. “Can I Give My Dog Benadryl and If So, How Much?”, August 20, 2015, Accessed June 18, 2020.

3)      Clark, Mike. “How Much Benadryl Can I Give My Dog?”, (no publish date), Accessed June 18, 2020.

4)      “How much Benadryl can I give my dog?”, February 14, 2020, Accessed June 18, 2020.

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