dogs sitting next to bottle and spray of Benadryl

Can You Give Dogs Benadryl?

Posted by Elizabeth Racine D.V.M. on

dogs sitting next to bottle and spray of Benadryl

If your dog experiences allergy symptoms like itching, you may have wondered “can I give Benadryl to my dog?” 

You can, in fact, give Benadryl to dogs, but with a few caveats. Before you give your dog Benadryl, make sure you know the ins and outs of this common antihistamine.  

What is Benadryl?

Benadryl is the brand name of the drug diphenhydramine, which is an antihistamine. "Histamine" is a compound released by cells in response to injury or during allergic or inflammatory reactions. Histamine is part of the process that causes those familiar allergic symptoms like sneezing, watery eyes, swelling, hives, and itching.

An antihistamine (like diphenhydramine) relieves these symptoms by blocking the action of histamine.  

Diphenhydramine is available as an over-the-counter medication in many different forms, one of the most common of which is the brand name Benadryl. Benadryl tablets come in various dosages. Liquid Benadryl is another option.

Generic diphenhydramine products are also available.

What is Benadryl Used for In Dogs?

dog scratching ear in golden light

In dogs, Benadryl is commonly used to treat mild itching from environmental allergies. It may also be used as a pre-medication for dogs prone to allergic reactions to vaccinations. It might also be used as treatment for allergic reactions to vaccines, insect bites, stings, or other causes. 

Benadryl may also be used to prevent nausea from car sickness, although it is less effective than other antihistamines and anti-emetics like Dramamine and Cerenia, respectively. 

Because it does have a mildly sedating effect, it is also used as a sedative for travel or stressful events. However, Benadryl does not have any anti-anxiety effects, making it a poor choice for the management of fear and anxiety in dogs

Many dogs also develop a tolerance to Benadryl over time, so it may not be an appropriate choice for long-term use.

What Are The Side Effects of Benadryl Use in Dogs?

cute pug laying down flat

The main side effect of Benadryl in dogs is mild sedation. This is sometimes the desired effect when Benadryl is used for travel or stressful events, but some owners dislike seeing their pet groggy and “out of it."

Other side effects from Benadryl administration can include:

  • Agitation (particularly at higher doses)
  • Behavioral changes
  • Loss of appetite
  • Vomiting
  • Constipation
  • Diarrhea
  • Dry mouth
  • Urinary retention
  • Dilated pupils
  • Elevated heart rate
  • Hypersensitivity reactions

Is Benadryl Safe for Dogs?

In general, Benadryl is safe for most dogs. However, Benadryl should be used with caution. Benadryl should not be used in patients with asthma attacks or in any patient with a known hypersensitivity to Benadryl.

Benadryl should be used with caution in patients with conditions such as:

  • Seizures
  • Glaucoma
  • Prostatic hypertrophy
  • Urinary bladder obstruction
  • Pyloroduodenal obstruction
  • Liver disease
  • Hyperthyroidism
  • Urinary retention
  • Intestinal atony
  • Cardiovascular disease
  • High blood pressure
  • Hypertension
  • Chronic obstructive pulmonary disease

If your dog has one of these conditions or another health condition, it’s best to talk to your veterinarian prior to using Benadryl for your dog to ensure that the product will be safe and effective.

Some formulations of diphenhydramine contain decongestants or other medications to aid with cold and allergy symptoms in humans. These medications are NOT safe for dogs and should not be given to your pets.

If you choose to give Benadryl to your dog, make sure you purchase the original formula only, as this does not have added medications.

Benadryl Dosage for Dogs

The dose of Benadryl in dogs depends on your dog’s weight and the desired effect. 

Before giving your dog Benadryl, it’s best to consult your veterinarian to determine the correct dosage. This is also a good time to let your veterinarian know what is going on with your dog – itching, car sickness, allergic reaction, etc – so that it can be documented in your pet’s medical record.

In general, you should never give your pet any over-the-counter medications or supplements without first consulting your veterinarian for advice. This is particularly important if your pet has any health conditions or if your pet is on any medications which could interact with the medication you wish to give.

When Benadryl Is Not Enough

Benadryl can help with mild itching and inflammation in dogs and may be useful as a mild sedative in certain situations; however, Benadryl may not be strong enough to ease your dog’s discomfort. 

If this is the case, it’s best to see your veterinarian for an examination. Your veterinarian will take a thorough history and perform a full head-to-tail examination. Your veterinarian may recommend some additional diagnostic testing to determine the underlying cause of your dog’s discomfort. 

Once your dog’s condition has been appropriately diagnosed, your veterinarian will develop a comprehensive treatment plan including prescription medication if necessary.

So, What's The Verdict? 

Holding a pill bottle (benadryl)

Benadryl is generally safe and effective for dogs with mild itching and allergy symptoms, and for use as a mild sedative. 

However, you should always consult your veterinarian prior to starting any new medication for your dog. You should also consult your vet if your pet’s symptoms persist despite the use of Benadryl, as a stronger medication may be necessary to manage your pet’s condition. 

Do not use Benadryl if your pet has underlying health issues or takes medication that may react with Benadryl. If your dog experiences side effects from Benadryl, stop giving the medication and contact your veterinarian right away for further advice.


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Elizabeth Racine D.V.M. is a small animal veterinarian with a passion for improving the lives of pets. She has worked in the veterinary field in various roles for more than a decade, with professional interests in behavior, nutrition, and palliative care. As a writer, her work has been featured by several world-renowned pet health and wellness brands. Dr. Racine shares her home with her dog Dasher - a beagle with his own storied career training new veterinary students - and her trouble-making orange cat named Julius.

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