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Safe Zyrtec Dosage for Dogs (2023)

Medically reviewed by Dr. Sara Ochoa, DVM

Is there anything worse than watching your furry friend dig and scratch at his skin until it’s raw? I have a friend who tried everything to find relief for his dog.

Prednisone was prescribed for a short period of time, but there were some downsides to the treatment.

Prednisone (a steroid) works wonders for allergic reactions, but it’s only available by a prescription and can cause:

  • increased thirst
  • increased urination
  • increased hunger
  • panting
  • lethargy
  • development or worsening of bacterial skin infections.

Allergies can affect dogs of all ages. The choice of treatment depends on the severity and cause of the symptoms. If your dog has seasonal allergies causing pain and itching, Zyrtec could be a good treatment option.

If you’re considering Zyrtec for your dog, keep reading. We’ll discuss its safety, uses, benefits, side-effects, dosage, and potential drug interactions.

What is Zyrtec?

Browse any local drug store and you will likely see Zyrtec on the shelf. That’s because it was formulated for use on people. Veterinarians use the medication “off-label” to treat allergic reactions in dogs because of its safety profile, availability, and cost.

Zyrtec is a non-sedating antihistamine that is available over-the-counter. This second-generation antihistamine typically comes with fewer side-effects and doesn’t have the same sedating effect that Benadryl (a first-generation antihistamine) does.

The antihistamine properties in the drug work by blocking receptors on blood vessels, tissues, and the lungs. Allergy symptoms flare when histamine is released throughout the body.

It’s probably fair to say we’ve all experienced a bug bite at one point in time. Most of us don’t even feel the initial sting or bite. It’s only when the skin becomes inflamed and itchy that we realize there’s a problem.

Controlling the “itch” factor

Just one mosquito bite can drive me insane. You try not to itch, but it’s almost impossible to ignore.

Dogs suffering allergic reactions go through a similar scenario, except it’s often much worse for them. The intense itch is caused by the release of histamines.

In order to control the release of histamines, drugs like Zyrtec help by preventing the histamine from binding to receptors. If they can’t be released, they can’t cause so much agony.

What Causes Allergies in Dogs?

Dogs can develop different types of allergies, including allergic dermatitis (skin allergies), food allergies, and acute allergic reactions.

Common causes of allergies and/or inflammatory responses in dogs include:

  • Flea Bites (some dogs are allergic to flea saliva)
  • Grass
  • Pollen
  • Food sources (food allergies can result in itchy skin and other symptoms)
  • Environmental
  • Dust mites
  • Weeds
  • Bee sting

The most serious of all is an acute allergic reaction. Severe reactions to vaccines, bee stings, or other allergens can cause the dog to go into anaphylactic shock, which is a life-threatening emergency.

Zyrtec is safe for dogs with allergies

Is Zyrtec Safe for My Dog?

Zyrtec is considered a safe way to treat allergies in most dogs. That said, it’s really important not to administer Zyrtec without your veterinarian’s approval.

Dogs with underlying conditions can look and act perfectly fine.

Unfortunately, that doesn’t mean there isn’t a health condition lurking beneath the surface. The following are some examples of when not to give your dog Zyrtec or other over-the-counter antihistamines.

Avoid Zyrtec-D in Dogs

Zyrtec-D was specifically developed for human consumption and includes pseudoephedrine. The ingredient relieves congestion in humans but can cause serious complications in dogs.

Pseudoephedrine over stimulates the central nervous system and heart. It can cause canine seizures, heart failure, and death in some dogs.

Zyrtec should not be given to some dogs

Zyrtec can cause urinary retention and should not be given to dogs with kidney disease. It should also be avoided in dogs with medical conditions including:

  • Glaucoma
  • Seizure Disorders
  • Difficulty urinating
  • Dogs with certain heart conditions
  • Older dogs
  • Working dogs
  • Pregnant dogs
Zyrtec is considered safe for dogs

The Benefits of Zyrtec for Dogs

Veterinarians have good reasons for prescribing Zyrtec for dogs, including:

Second-Generation Antihistamine

Second-generation antihistamines, including Allegra (fexofenadine), Claritin (loratadine), and Zyrtec were developed to reduce or eliminate the effects of sedation and adverse side-effects in people with allergies.

Although first-generation antihistamines tend to be stronger, they can also come with additional side-effects.

Itch Relief for Dogs

Zyrtec is often used off-label by veterinarians to relieve the itching and pain caused by allergies or skin conditions.

Allergies can cause similar reactions in dogs and people. If your dog has allergies, you may notice the following signs:

  • Irritated skin
  • excessive itching
  • water eyes
  • rubbing the face
  • biting at their legs or paws
  • skin infection
  • fur loss

A study published in The Canadian Veterinary Journal assessed the effects of Zyrtec on canine atopic dermatitis, the second most common cause of allergic skin disorders in dogs

Excellent Safety Profile

Zyrtec is well tolerated in dogs and has a wide safety margin. This means it’s unlikely to cause issues even if given in higher doses.

One and Done

A major advantage of using Zyrtec for dogs is that it requires a single daily dose. Other antihistamine products require at least two or three doses per day to produce noticeable results.

What is the Correct Zyrtec Dosage for Dogs?

Remember to discuss Zyrtec with your veterinarian. This antihistamine is considered safe in otherwise healthy dogs. It may not be safe for dogs with some underlying health conditions. In addition, there can be drug interactions (discussed further in this post).

Zyrtec is Available in 5 and 10 mg Tablets

The dosage of Zyrtec will depend on the size of your dog, the condition being treated, and the severity of the condition.

Generally speaking, dogs between 10 and 50 pounds can take 10 mg pills. Dogs under 10 pounds should only take 5 mg.

Dogs over 50 pounds could take two 10 mg tablets (20 mg) and very small dogs under 5 pounds could take 2.5 mg (half of a 5 mg pill or a quarter of a 10 mg pill).

Disclaimer: The dosing guidelines on the package are designed for human use.

Ask a veterinarian to suggest the best dosage for your dog. Every dog is different and every situation is different. While there is a wide safety margin, it’s still a very good idea to consult with a professional.

Remember, certain underlying conditions and medications can cause complications.

Are There Any Side Effects in Zyrtec for Dogs?

Zyrtec is a second-generation antihistamine with few to no side effects. In rare cases, your dog may experience:

  • Excessive salivation or drooling
  • Hyperactivity
  • Urine retention
  • Nausea and vomiting
  • Constipation

Potential Drug Interactions

Central nervous system depressants are known to interact with cetirizine. These include diazepam and alprazolam.

It’s also possible for drug interactions to occur in dogs on certain vitamins, supplements, and herbal treatments. Always tell your veterinarian of all medications your dog is on.

Natural Alternatives to Zyrtec

Some of the methods mentioned below can help to reduce itch in dogs. They don’t, however, take care of the problem. The only way to relieve a dog’s allergies is to determine the exact cause and avoid it.

Any treatments for itchy skin, including the relief provided by antihistamines, only treat the symptoms of allergies and not the allergies themselves. Always talk to a veterinarian to determine the cause of your dog’s allergic reaction.

Oatmeal Baths and Other Alternative Options

Oatmeal is more than a hearty breakfast choice, it can also help to ease the irritation and itch from allergies.

Parents have been using it forever to treat children with bug bites, chicken pox, and other skin irritations. It can also be used on dogs.

In order for oatmeal to work, it should be mixed into a paste and smoothed onto the skin. This can be done in the bath to avoid a mess.

Summary – Keep Your Dog Allergy-Free

Treating severely itchy skin and pain in dogs is vital for their quality of life.

However, it’s important to understand that antihistamines don’t solve the underlying problem. This is one reason why it’s so important to visit a veterinarian for a diagnosis.

Even though Zyrtec is considered safe for dogs, there are always exceptions.

Make sure your dog is healthy and free from underlying conditions before administering Zyrtec to your dog. You’ll want to confirm the correct dosage with the veterinarian to be on the safe side.

Works Cited

MORIELLO.KAREN. Merck Veterinary Manual: Itching (Pruritus) in Dogs – Dog Owners – Merck Veterinary Manual., Accessed 19 Oct. 2022.

Vca: Diphenhydramine | VCA Animal Hospital., Accessed 19 Oct. 2022.

Veterinary Place: Zyrtec for Dogs | Veterinary Place., Accessed 19 Oct. 2022.

Hensel, Patrick, et al. BioMed Central: Canine Atopic Dermatitis: Detailed Guidelines for Diagnosis and Allergen Identification – BMC Veterinary Research., 11 Aug. 2015,

Brennan, Kendall. Canna-Pet®: Side Effects of Zyrtec for Dogs | Canna-Pet®., 27 Nov. 2017,

Vca: Cetirizine | VCA Animal Hospital., Accessed 21 Oct. 2022.

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