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Benadryl For Dogs: What You Need To Know

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Benadryl For Dogs: What You Need To Know

Benadryl is one of the most popular over-the-counter allergy medications on the market. If you've ever snuffled up once the spring winds start blowing or experienced mild symptoms after a brush with a specific allergen (dander, grass, insect bites), you've probably been offered Benadryl. That is if you don't already take it regularly yourself.

But did you know that many dog owners give their furry friends liquid Benadryl, and not just as an allergy medication? Benadryl (generic name diphenhydramine) has been used to treat a wide swath of symptoms in dogs, from motion sickness and anxiety to as an adverse reaction inhibitor after heartworm treatment or mast cell therapy. 

Innovet has put together a complete guide to the information and resources you need to know about before trying diphenhydramine on your dog, from dosage to vet recommendations to potential side effects of Benadryl. Remember that before ever putting your dog on a new drug, you should always consult your veterinarian on how much benadryl for dogs should be given.

Benadryl for Dogs: What You Need to Know | Innovet Pet

What is Benadryl?

To understand what the diphenhydramine drug known as Benadryl is, you must understand what an antihistamine is and understand what an antihistamine is and what a histamine is. Histamines are produced by the immune system and act as part of the body's natural defense against allergens. When an allergen enters the body, histamines are released into the bloodstream in order to neutralize it. However, sometimes histamines can be produced in excess, leading to an allergic reaction.

The reason you get allergy symptoms such as sneezing, sweating, and watery-eyed symptoms during an allergic reaction are because histamines are trying to expel the foreign allergen from your body. Sometimes, these chemicals get a little carried away; however, the body cannot reign them fast enough. That's how severe allergies can cause symptoms such as the closure of the breathing passage and cardiac arrest.

This is where antihistamines come in. These are the compounds present in high dosages of diphenhydramine. What they do is block cells' histamine receptors, meaning allergic reactions are prevented from occurring. Many doctors and veterinarians are encouraging Benadryl use in their human and dog patients, understanding that when allergic reactions come, they can come on suddenly and severely, leaving little time for crisis response. 

For pet parents, allergies are a common issue. Dogs can suffer from seasonal allergies, food allergies, and environmental allergies, among other things. While some dog allergies are more serious and require medication like an Epipen, many are not life-threatening but still cause troubling symptoms. In these cases, dog owners often keep a supply of dog Benadryl on hand to relieve their dog's symptoms.

However, it is important to be aware of the correct dosage of dog Benadryl for your dog's body weight and severity of symptoms. Giving your dog too much Benadryl can be dangerous, so it is always best to consult with your veterinarian before giving your dog any medication.

Benadryl for Dogs: What You Need to Know | Innovet Pet

Is Benadryl Safe For Dogs?

It should be said that the FDA has not cleared Benadryl for veterinary use. Still, most veterinarians you talk to will tell you that a reasonable dosage on a clearly afflicted dog will do nothing but alleviate their symptoms, actually making them safer than had they not taken the drug. Benadryl can be a perfectly safe and healthy course of treatment for anxiety, allergies, and more in your dog, but there are a few things to check first.

It's important to keep a running list of any medications including over-the-counter drugs your dog might already be on. Veterinarians frequently prescribe medications like nervous system depressants and anticoagulants after dogs have surgery. But these medications can interact poorly with Benadryl, sometimes worsening the symptoms of allergic reaction.

Keep in mind that every dog is different. Your dog's size, body mass, diet, exercise regimen, and general temperament will factor into the drug's effect on them. What's safe for a German Shepherd isn't necessarily going to be safe for a Pekinese. This is another reason to consult your veterinarian before you give your dog Benadryl.

Benadryl for Dogs: What You Need to Know | Innovet Pet

When is Benadryl Prescribed For Dogs?

Benadryl can be prescribed to dogs by a licensed veterinarian for a number of symptoms. Below are four of the most common:


If Benadryl is good enough for your sneezing and snuffling, it's good enough for your dog. The canine immune system is similar enough to humans' so that Benadryl can be a safe and effective treatment for mild to moderate allergic reactions. If the allergy symptoms are severe, of course, see a veterinarian immediately.


Too many dog owners have learned to resort to extreme measures to get through New Year's Eve and the Fourth of July. That is, to get their dogs through the trauma of fireworks. Many dogs get crippling anxiety from loud noises, over-activity, and more. Benadryl has a unique effect on serotonin, which makes you drowsy. Sleepy dog = less anxious dog.

Motion Sickness

Many dog owners have turned to Benadryl as an effective way to relieve their dog's symptoms, including runny nose and itchiness. Benadryl is a medication that is designed to modulate serotonin levels and reduce inflammation, both of which can be helpful in soothing dogs who are prone to nausea on long car rides.

The anti-inflammatory properties of Benadryl can help to reduce the swelling of the dog's airways, making it easier for them to breathe. In addition, the medication can also help to relieve itchiness by inhibiting the production of histamines. While Benadryl is generally considered safe for dogs, it is always best to speak with a veterinarian before giving any medication to your pet.

Mast Cell Tumors

Mast cells are white blood cells that play a role in responding to allergic reactions. It's no surprise that when a dog develops a tumor in their mast cell that histamines are overproduced, sending dogs down a spiral of allergic reactions. Veterinarians often prescribe Benadryl to dogs to combat this condition.

Benadryl Dosage For Dogs

Okay, Benadryl is safe for your dog, and can be used to treat several symptoms. But how much should you give them, and in what form? These are great questions to consider with your veterinarian, but we'll go through the basics here.

Benadryl is generally prescribed to dogs by veterinarians in tablet form. Wrap it up in their favorite treat, and they'll gobble it down without a second thought. If your dog is on the discerning side or is known for being a pill splitter, ask your vet about liquid Benadryl that you can mix into water.

How much of the drug you give your dog depends entirely on their size (but don't forget those other factors - diet, exercise, and temperament). A Benadryl overdose can result in constipation, seizures, and rapid heart rate. The dosage weight guide is as follows:

30lbs or lighter - 10mg dose

30 to 50 lbs - 25 mg dose

Over 50 lbs - 50 mg dose

If you're not sure how much Benadryl to give your dog, it's best to err on the side of caution and consult your veterinarian. If your dog does have a severe reaction, it may need to be treated at an emergency veterinary hospital immediately. If you're ever confused about what these dosage sizes look like, you can call your veterinarian's office to confirm.

Benadryl for Dogs: What You Need to Know | Innovet Pet

Possible Benadryl Side Effects in Dogs

While it is generally safe to administer Benadryl as an allergy medication to dogs, there are potential side effects to watch out for.

Some of the most common and least concerning side effects include sedation, dry mouth (and alternatively, hypersalivation), and heightened heart rate.

Some side effects that are on the troublesome side can be diarrhea and vomiting (both rare) and urinary retention. If your dog suffers from prostatic hypertrophy or bladder neck obstruction, consult your veterinarian. It may not be a good idea to use Benadryl for dogs. 

If your dog lives with any of these other conditions prior to ingesting the Benadryl, check with your vet first, but consider holding off: 

  • Glaucoma
  • Severe Heart Failure
  • High Blood Pressure
  • Allergic Lung Disease
  • Pregnancy

If a side effect is going to pop up, it's almost always going to pop up within the first hour after dosage. So keep an eye on your dog, and if their condition alarms you, remain calm and call a vet.

CBD oil for dogs

Alternatives To Benadryl For Dogs

Benadryl is generally a safe, fast-acting, and effective medication. But it isn't right for everyone. If your dog lives with any of the previously mentioned conditions, or you administered the medication to them, and they reacted adversely, there are alternatives to consider.

CBD has proven to be a remarkable treatment for all the same conditions Benadryl is prescribed for in dogs, from allergies to anxiety. The many benefits of CBD begin with the fact that it is a naturally-derived compound. While most vets would tell you Benadryl is perfectly safe if you're still nervous, the potential side effects of CBD pale compared to that of the medication.

CBD's natural active ingredients can also improve your dog's overall health and beauty, from promoting brightness in dull coats to soothing dry skin to healing cracked paw pads. CBD also boasts the benefit of micro-dosability. Whether you're administering Innovet's PurCBD+ PhytoCannabinoid Oil or the delicious Hemp Soft Chews, you can control how much CBD your dog is getting through tincture measurement down to the last drop.

It's not the only alternative on the market, but CBD is certainly one of the most exciting new products for treating allergies, anxiety, motion sickness, and more in your pet. The volume of clinical research on CBD's active ingredients in pets also testifies just how effective it can be.

Benadryl for Dogs: What You Need to Know | Innovet Pet

Doing What's Best for Your Dog

There is a trove of peer-reviewed clinical research and first-hand accounts of the benefits of Benadryl for dogs online, and you should spend some time looking through it. What you absolutely must do before considering Benadryl for dogs is consult your veterinarian.

Get to know your dogs' allergies, tabulate the right Benadryl dosage (or the right CBD dosage), and sit back and discover how much happier your dog's life could be.

Innovet Pet Products brings pet owners together with licensed veterinarians, health, hygiene, and wellness experts to provide you with the best information. All our efforts are focused on developing the safest, most innovative CBD products, grooming solutions, and animal necessities and educating our customers about them in an engaged, shame-free way.

To find out more about Innovet's best-selling health products, pet accessories, our dosing calculator, and to read about our story, you can visit our website.

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