Antihistamines for Dogs

Posted by Lianne McLeod D.V.M. on

Antihistamines for Dogs

Dogs,  much like their human companions,  can suffer from a variety of allergies.  These allergies can manifest in many ways,  from skin irritations and gastrointestinal issues to respiratory distress.  As pet parents,  it’s crucial to understand these allergic reactions and how to manage them effectively.  One common method of managing dogs' allergies is using antihistamines, specifically dog’s Benadryl.

In this article,  we’ll delve deeper into antihistamines,  the use of Benadryl for dogs, when it’s appropriate to use,  how much to give your dog,  potential side effects to watch out for,  and more.  In addition, we will explore more options apart from Benadryl and suggest preventive actions you can implement to alleviate your dog's allergy symptoms.

What are Antihistamines?

Antihistamines are medications frequently utilized to alleviate allergy symptoms in both humans and our furry canine companions. They function by inhibiting the actions of histamine; a compound that is naturally produced in the body during an allergic response and leads to manifestations, like itchiness, inflammation, and redness.


How Antihistamines Work for Dogs?

When a dog is exposed to an allergen, a substance that triggers an allergic reaction, the body responds by releasing histamine. This histamine then binds to receptors on the surface of cells, causing them to swell and leak fluid. Which results in the common symptoms of an allergic reaction, such as itching, hives, and inflammation.

Antihistamines work by blocking these histamine receptors, preventing histamine from binding to them and triggering the dog's symptoms of an allergic reaction. While antihistamines can be a useful tool for managing allergies such as seasonal allergies in dogs, it’s important to note that they do not cure allergies, they simply help to manage the symptoms.

Benefits of Dog's Antihistamines

Antihistamines offer several benefits to dogs apart from allergy relief. They include:

Sedative Effects: Many antihistamines, including dog’s Benadryl, have a mild sedative effect. This can be beneficial for dogs who are anxious or overly excited, as it can help calm them down.

Treatment of Motion Sickness: The sedative effect of certain antihistamines can also help alleviate motion sickness in dogs, making car or plane travel more comfortable for them.

Ease of Administration: Antihistamines are typically available over the counter and can be easily administered orally. Some come in flavored varieties or chewable forms that may be more palatable to dogs.

Safety: When administered at the correct dosage, antihistamines are generally safe for most dogs. However, it’s important to consult with a veterinarian before giving your dog an antihistamine to ensure it’s safe for your pet’s specific needs and health conditions.

Availability: Antihistamines are widely available and can be found in most pharmacies and pet supply stores.

antihistamines for dogs

What is Benadryl?

Benadryl, known by its generic name diphenhydramine, is an over-the-counter medication that is commonly found in most medicine cabinets. It’s primarily used to treat allergy symptoms in both humans and dogs. The active ingredient in Benadryl, diphenhydramine, is an antihistamine that works by blocking the effects of histamine, a substance in the body that causes acute allergic reactions such as itching, redness, and swelling.

Is Benadryl Safe for Dogs?

Yes, the dog’s Benadryl is safe for most dogs when given at the correct dosage. However, it should not be given to dogs without first consulting with a veterinarian. Certain health conditions or dog allergies medication your dog is currently taking could interact negatively with Benadryl.

When to Give My Dog Benadryl

Benadryl can be a useful tool for managing a variety of conditions in dogs, but it’s important to know when it’s appropriate to use. Here are some situations where Benadryl might be used for dogs:

woman and her dog

Allergic Reactions: One of the most common uses of Benadryl in dogs is to treat allergic reactions. These could be reactions to things in the environment, seasonal allergies, food allergies, or reactions to insect bites or stings. The antihistamine works by blocking the effects of histamine, a substance in the body that causes allergic symptoms such as itching, redness, and swelling.

Anxiety and Insomnia: The sedative properties of Benadryl can also make it useful for treating anxiety and insomnia in dogs. It can help calm anxious dogs and help them sleep.

Motion Sickness: Some dogs experience motion sickness when traveling by car or plane. The sedative effect of Benadryl can help to alleviate these symptoms.

Skin Conditions: Benadryl can also be used to treat certain skin conditions in dogs, such as hives or itching caused by contact with certain substances.

Vaccine Reactions: Some dogs may have a mild allergic reaction to certain vaccines. Benadryl can be used to alleviate these symptoms.

dog benadryl

How Much Benadryl Can I Give My Dog?

The normal suggested Benadryl dosage for dogs is one milligram per pound of body weight, given two or three times a day. For example, let us consider a small dog that weighs 10 pounds, you would administer the dog 10 milligrams of Benadryl.

With regard to liquid Benadryl dosage in dogs, its concentration is often at 2.5 milligrams per milliliter. To find out how much liquid Benadryl to give your dog, you would divide the total dosage by the concentration. For instance in the example above, 10 mg divided by 2.5 milligrams per milliliter you get 4 milliliters as the recommended dosage. This dosage can be given two or three times a day, or every 8 to 12 hours.

However, it’s important to always consult with your veterinarian before giving your dog Benadryl or any other medication, to ensure it’s safe and the correct Benadryl dosage is given for your pet’s health condition.

Side Effects of Benadryl

While Benadryl is generally considered safe for most dogs when given at the correct dosage, it’s important to be aware of the potential side effects and risks associated with its use.

Common Side Effects

Drowsiness is the main side effect of Benadryl. Its sedative nature can soothe and help ease dogs with nervousness and too much excitement. Nevertheless, it leads to a sluggish or non-responsive dog.

Other common side effects can include dry mouth and urinary retention. In some cases, dogs may also experience an upset stomach or loss of appetite after taking Benadryl.
important update

Serious Side Effects

Sometimes dogs might have an allergic response to the dog’s Benadryl.  Indications of a reaction may involve trouble with breathing, facial or tongue swelling, and the appearance of hives. If your dog encounters any of these signs it is crucial for you to seek veterinary assistance.

Additionally, in some cases, dogs may experience an overdose if given too much Benadryl. Symptoms of a dog’s Benadryl overdose can include agitation, rapid heart rate, confusion, and seizures. If you suspect your dog has overdosed on Benadryl, seek veterinary care immediately.

Interactions with Other Medications

Benadryl can interact with other medications your dog may be taking. For example, it can enhance the effects of certain medications that depress the central nervous system, such as opioids or sedatives. It can also interact with certain antifungal medications and other antihistamines.

Alternatives to Benadryl

There are many alternative medicines to Benadryl for dogs. These include other antihistamines and natural treatments.

natural alternatives

Other Antihistamines

Cetirizine: Cetirizine is an antihistamine used for treating and preventing itching associated with atopic dermatitis, hives, and insect bite reactions in cats and dogs. It is regarded as less sedating than other antihistamines. Dogs are typically administered between 0.12 and 0.22 milligrams per pound to control allergies.

Loratadine: Your vet may also prescribe your dog loratadine, which is another antihistamine. It’s generally safe and beneficial when given at the appropriate dosage. The recommended Claritin dose for dogs is between 0.1 and 0.55 milligrams per pound of body weight once or twice per day.

Fexofenadine: Fexofenadine is a popular trade name for second-generation antihistamines applicable in dogs and cats with allergy symptoms such as itching and other signs related to allergic conditions. Fexofenadine is considered less sedating than other antihistamines. In dogs, Fexofenadine is dosed at 1 to 2.5 milligrams per pound of body weight, every 12 to 24 hours.

Natural Alternatives

Quercetin: Quercetin is a powerful flavonoid found in many fruits and vegetables. It has antihistamine effects, making it an effective treatment for allergies. Quercetin is so effective in helping allergies that it’s known as "Nature’s Benadryl". It doesn’t have the risks and side effects that come with pharmaceutical Benadryl. Quercetin has the ability to inhibit or significantly decrease the production of histamine in the body,  thereby alleviating allergy symptoms.

Aloe Vera: Aloe Vera is a plant with various medicinal properties. It can be used as a natural alternative to Benadryl for dogs. Aloe Vera has anti-inflammatory properties that can help alleviate common symptoms treated by Benadryl.

CBD Oil: CBD oil is derived from the hemp plant and is known for its therapeutic properties. It could alleviate the common symptoms treated by Benadryl tablets, making it a natural alternative.

Dietary Changes: Sometimes, allergies in dogs can be managed by making dietary changes. Certain foods are known to trigger allergic reactions in dogs, such as wheat, soy, and corn. By identifying and eliminating these allergens from your dog’s diet, you may be able to reduce or eliminate their allergy symptoms.

Environmental Changes: Environmental allergens such as tree, grass, and weed pollens, mold spores, dust, dust mites, cleaning products, insect bites, and insect control products can trigger allergies in dogs. Minimizing your dog’s exposure to these allergens can help manage their allergies. These changes can involve keeping your home clean, using natural, non-chemical products and cleaners in your home and yard, and limiting the amount of time your dog spends outside when pollen counts are high.

Where to get Antihistamines

Antihistamines are a type of medication that can be obtained in several ways:

shopping logo

Over-the-counter (OTC) Purchases: Many antihistamines are available over the counter, meaning they can be purchased without a prescription. These can be found in most pharmacies, drug stores, and even some supermarkets. Over-the-counter antihistamines include popular brands like Benadryl, Claritin, Zyrtec, and Allegra.

Online Shopping: With the advent of e-commerce, antihistamines can be conveniently purchased online. Numerous online pharmacies and retailers offer a wide range of antihistamines that can be delivered right to your doorstep.

Prescription Medications: Some antihistamines or stronger doses may require a prescription from a healthcare provider or veterinarian. These are typically used for more severe or chronic allergic conditions.

Veterinary Clinics: For pet-specific antihistamines or dosages, these can often be obtained directly from your veterinarian’s office. They can provide guidance on the appropriate type and dosage based on your pet’s specific needs and health condition.

Compounding Pharmacies: In some cases, if a specific dose or formulation of an antihistamine is needed, for example, if a smaller dose is needed for a small dog or if a flavored version is preferred, a compounding pharmacy may be able to create a custom formulation.

Although antihistamines are generally considered safe for dogs when administered at the appropriate dose, it is crucial to seek advice, from a veterinarian before giving your furry friend any antihistamines. So as to ensure that it aligns with your pet's requirements and health condition.


Q: Which one is more effective for dogs; Benadryl or Zyrtec? 

A: Both Benadryl and Zyrtec are effective in treating allergies in dogs. However, Zyrtec is less sedating than Benadryl.

Q: Are human antihistamines safe for dogs? 

A: Some human antihistamines like Benadryl and Zyrtec are safe for dogs but should be given under a vet’s supervision.

Q: Is Zyrtec a better option than Benadryl for dogs? 

A: Zyrtec can be a better option for long-term use as it’s less sedating than Benadryl.






6. Benadryl For Dogs: What to Know About Using This Medication For Dogs (

← Older Post Newer Post →

Leave a comment


Lianne McLeod, DVM, is a former writer for The Spruce Pets, contributing articles for 11 years. Before Dr. McLeod began writing about pet care, she worked several years in small animal practice. She has written extensively about the care and keeping of exotic pets and pet health care. She now researches water quality and chronic disease at the University of Saskatchewan. Lianne McLeod earned her Doctorate of Veterinary Medicine from the Western College of Veterinary Medicine at the University of Saskatchewan. She also received a Bachelor of Science degree in biology from Simon Fraser University. She continued her education and received a Ph.D. in Epidemiology from the University of Saskatchewan. Now, she splits her time between her family, research and writing about pet health for all the animal lovers out there.
RuffRuff App RuffRuff App by Tsun