Most dog owners have likely heard of Benadryl. It is an incredibly popular medication that is used primarily for alleviating itchy skin and other seasonal allergies.

Additionally, Benadryl has been used to treat motion sickness in dogs and provide mild sedation.

Although many veterinarians consider Benadryl to have a wide safety margin, there are still dangers and adverse reactions associated with the drug that pet owners should be aware of.

What is Benadryl?

Benadryl is the brand name for diphenhydramine. Diphenhydramine reduces the effects of histamine within a dog's system.

Histamine is the compound that's released in response to an injury, or in allergic and inflammatory reactions. Because it works to mitigate histamine, Benadryl, just like cetirizine for dogs (a.k.a. Zyrtec for dogs) is known as an antihistamine--a term most pet parents are probably familiar with.

Diphenhydramine is categorized as a first-generation antihistamine, meaning that it can cross the blood-brain barrier. The blood-brain barrier protects the brain from harmful foreign substances, such as bacteria or viruses. This barrier does allow some substances (such as diphenhydramine) to pass through, however.

Diphenhydramine’s ability to cross the blood-brain barrier means that it is typically very effective. However, this ability also increases the risk of potential adverse reactions.

What does Benadryl treat in dogs?

Benadryl is a popular medication that is used to treat a variety of symptoms in dogs, including:

  • Allergies

  • Hives

  • Anxiety

  • Motion Sickness

Benadryl is sometimes also used in conjunction with treatments for:

  • Mast cell tumors

  • Heartworms

Benadryl can also be used to treat pain.

Let's explore some of these use cases in more detail.

Benadryl for Allergies

When we think about allergies, we typically think about red and itchy eyes, a runny nose, sneezing, etc.

Dogs have different symptoms when experiencing allergic reactions. In most cases, dogs show allergy symptoms on the skin’s surface. 

Although it's possible for your pup to show signs of allergies that are similar to those of humans, you'll want to make sure that your pup doesn't have a more serious condition at hand in such a situation. Nasal discharge, coughing, and inflamed eyes can be a sign of a slew of conditions in dogs, including respiratory infections. Therefore, it's important not to automatically assume that allergies are causing these symptoms.

Allergies in dogs include:

  • Seasonal allergies

  • Food allergies

  • Environmental allergies

  • Allergic reactions to snake bites

  • Allergic reactions to insect bites

Learn more about dog allergies here

Benadryl for Hives

Benadryl is also known to effectively treat hives in both dogs and humans.

Although pets with hives may look pretty miserable, we want to assure pet owners not to panic if their pup breaks out in hives, as the hives can be treated, typically without any complications.

Benadryl for Anxiety

A major side effect of diphenhydramine, the active ingredient in Benadryl, is drowsiness.

If your pup has anxiety, your veterinarian may prescribe Benadryl to help ease symptoms of anxiety and effectively help your anxious pup calm down.

Benadryl for Motion Sickess

Many pet owners may not know that Benadryl is often recommended for dogs who experience motion sickness.

Again, it causes drowsiness, which allows your pet to feel relaxed and calm down during normally stressful events such as car rides.

Treating Mast Cell Tumors with Benadryl

Mast cells are white blood cells that play a role in allergic reactions. When a dog has mast cell tumors, there is a mast cell degranulation, which causes a massive histamine release.

If your dog has a mast cell tumor, your veterinarian may recommend Benadryl to alleviate symptoms from the histamine release from the tumor cells.

Benadryl in Heartworm Treatment

Heartworm treatment involves the killing of adult heartworms. The death of the heartworms can trigger a serious allergic reaction. 

If your pup has to undergo heartworm treatment, your vet may recommend Benadryl to ease the symptoms associated with the treatment.

Benadryl Dosage for Dogs

Benadryl should only ever be administered in the tablet form when prescribed for dogs. There may be cases, however, when your vet okays administering Benadryl to your dog in liquid form.

As for dosage, Benadryl dosage is based on the dog's body weight.

Experts recommend 1mg of Benadryl per 1lb of body weight.

A 50lb dog, for instance, can receive 2 Benadryl tablets (which are 25mg each).

You can give your dog the recommended dosage 2-3 times a day (every 8-12 hours).

Benadryl typically takes effect within 30 minutes of administration. Of course, every dog responds differently to new medications, so it's important to talk to your veterinarian about the dose that is right for your particular pup.

Side Effects of Benadryl

Although Benadryl has been deemed to be safe when used appropriately, pet parents should always be aware of potential side effects when introducing a new medication into their dog's health regimen.

Always consult the website of the brand of medication you're using for the most up-to-date information about common uses and reported side effects. Some potential side effects of Benadryl use in dogs may include:

  • Dry mouth

  • Urinary retention

  • Increased heart rate

  • Sedation

  • Hypersalivation

  • Rapid breathing

  • Increased appetite

  • Decreased appetite

  • Vomiting

  • Diarrhea

Benadryl Overdose

A Benadryl overdose can cause hyperexcitability of a dog’s central nervous system. It is critical to seek proper medical attention if you think that your dog may be experiencing an overdose.

Signs of a Benadryl overdose include:

  • Dilated pupils

  • Seizures

  • Rapid heart rate

  • Irregular heartbeat

  • Agitation

  • Confusion

  • Constipation

  • Muscle tremors

When to Avoid Benadryl

Dogs with glaucoma, high blood pressure, and cardiovascular disease should avoid Benadryl, as it can worsen their condition.

Furthermore, dogs with the following conditions should not receive Benadryl:

  • Angle-closure glaucoma

  • Allergic lung disease

  • Bladder neck obstruction

  • Heart failure

  • Prostatic hypertrophy

  • Pregnancy

  • Nursing

  • Hyperthyroidism

  • Seizures

Natural Alternatives for Diphenhydramine

Luckily, these days, there are more holistic options than ever to help support your dog's health and happiness.

Here are some of the more popular alternatives that pet parents opt for when treating their dog's itchy skin.

Oatmeal

Oatmeal can serve as a soothing home remedy for irritated and itchy skin. All you have to do is mix plain oatmeal and water until it forms a paste. Then massage the paste into your dog's skin and let it stay in place for 15-20 minutes. Then rinse the paste off with warm water.

Alternatively, you can draw a warm bath (we recommend using our bath assistant if your dog is not a fan of the tub) and add the oatmeal directly to the water. Let your pup soak for 10-20 minutes to put their itchy skin at ease.

Baking Soda

Like oatmeal, baking soda is another popular alternative that pet parents turn to when treating itchy skin. Simply make a paste with baking soda and a little bit of water and then apply it directly to your dog's irritated skin, letting it sit for 20-30 minutes before rinsing it off.

Apple Cider Vinegar

Apple Cider Vinegar is a popular holistic alternative for a number of conditions, including itchy and irritated skin. It's a powerful antibacterial and anti-fungal treatment. Simply create a solution that's 50/50 apple cider vinegar and water and place it inside a spray bottle. Then spray your dog's irritated skin to help ease their discomfort. Never spray the solution on raw skin or open wounds, however, as this can be painful for your pup.

Chamomile and Green Tea

Chamomile and green tea have roperties that can soothe irritated skin and help your dog feel much better. Simply draw a warm bath and drop several herbal tea bags in the water to let them steep. After 3 minutes, remove the tea bags and then let your dog soak in the bath for 5-10 minutes.

When to Consult Your Vet

Many veterinarians and pet owners find Benadryl to be an effective antihistamine for mild to moderate allergic reactions.

However, if your pup is having an allergic reaction with facial swelling or difficulty breathing, it is imperative that you go straight to the vet.

Benadryl is not effective in serious cases of allergic reactions. Seeking medical intervention in a timely manner is extremely important for your dog's life if he’s having a serious allergic reaction.

A Final Thought

Benadryl is a popular medication that is used to treat a variety of symptoms in dogs, including allergies, hives, anxiety, and motion sickness. Benadryl is sometimes also used in conjunction with treatments for mast cell tumors and heartworms.

Although many veterinarians consider Benadryl to have a wide safety margin, there are still dangers and adverse reactions associated with the drug that pet owners should be aware of. Pet parents should always consult the website of any drug their dog is prescribed to access the most up-to-date information about common uses and potential side effects.

Always follow recommended dosage guidelines when it comes to Benadryl for dogs. Experts recommend 1mg of Benadryl per 1lb of body weight. This dosage can be administered 2-3 times a day (8-12 hours apart). Pet owners should never exceed this dosage amount, as a Benadryl overdose can cause hyperexcitability of a dog’s central nervous system. Alternatively, pet parents can turn to several holistic alternatives in treating their dog's allergic reactions.

Frequently Asked Questions (FAQs)

What is Benadryl used for in dogs?

Benadryl is a popular medication that is used to treat a variety of symptoms in dogs, including allergies, hives, anxiety, and motion sickness. Benadryl is sometimes also used in conjunction with treatments for mast cell tumors and heartworms.

Is Benadryl safe for canines?

Although many veterinarians consider Benadryl to have a wide safety margin, there are still dangers and adverse reactions associated with the drug that pet owners should be aware of. Always follow recommended dosage guidelines (1mg of Benadryl per 1lb of body weight) and know the signs of Benadryl overdose in dogs.

Can my dog overdose from Benadryl?

A Benadryl overdose can cause hyperexcitability of a dog’s central nervous system. It is critical to seek proper medical attention if you think that your dog may be experiencing an overdose. Always follow recommended dosage guidelines (1mg of Benadryl per 1lb of body weight) when administering Benadryl to your dog.

How much Benadryl is toxic to a dog?

Experts recommend 1mg of Benadryl per 1lb of body weight. This dosage can be administered 2-3 times a day (8-12 hours apart). Pet owners should never exceed this dosage amount, as a Benadryl overdose can cause hyperexcitability of a dog’s central nervous system.

Is Diphenhydramine the same as Benadryl?

Benadryl is the brand name for diphenhydramine. Diphenhydramine reduces the effects of histamine within a dog's system, the compound that's released in response to an injury, or in allergic and inflammatory reactions.

How long does Benadryl last in a dog?

Benadryl usually takes effect within 30 minutes of administration. Experts recommend administering a dose of Benadryl every 8-12 hours as needed.

What is a safe dose of Benadryl for a dog?

Experts recommend 1mg of Benadryl per 1lb of body weight. This dosage can be administered 2-3 times a day (8-12 hours apart).

Can dogs take Benadryl everyday?

Experts recommend 1mg of Benadryl per 1lb of body weight. This dosage can be administered 2-3 times a day (8-12 hours apart).

Sources

https://pubmed.ncbi.nlm.nih.gov/15825733/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1661429/pdf/vetsci00275-0006.pdf

https://pubmed.ncbi.nlm.nih.gov/30779257/

https://www.certapet.com/benadryl-for-dogs/

https://www.veterinaryplace.com/dog-medicine/benadryl/

Written by Lily Velez. Reviewed for publication by JoAnna Pendergrass, DVM.