Giving Your Dog Zyrtec: How Much You Can Safely Give

Written by Marisa Wilson
Updated: October 29, 2023
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You may want to give Zyrtec to your dog for several reasons. And as with anything medical-wise that you will be giving them, you want to make sure that you have the correct dosage and understand what side effects are typical and when you should be concerned about them. It’s always good to get approval from your vet before you start treating an undiagnosed problem in your dog. A medical opinion helps make sure that the underlying cause is diagnosed so that you’re not treating something that may come across as minor but be far more severe. This guide will help you understand the proper dosage to give your dog and how to do it safely. 

What is Zyrtec?

Zyrtec is the brand name for an antihistamine medicine that treats issues such as skin and allergy symptoms that several factors can cause. The generic form of the drug is called cetirizine, and both versions work by blocking the histamine effects in the body. Histamine is a chemical released by the body because of certain substances, such as dust, food, or chemicals. It’s an immune response after exposure to those types of pathogens. The histamine then acts on a person’s eyes, nose, throat, lungs, skin, or gastrointestinal tract, causing allergy symptoms. It has been studied for its role in allergic reactions for a long time. 


Zyrtec is the brand name for an antihistamine medicine that treats issues such as skin and allergy symptoms.

©Carlos Yudica/

Side Effects

Zyrtec is usually well tolerated by dogs and doesn’t cross the blood-brain barrier, making sedative effects far less likely. If you want to take extra precautions to avoid sedative effects on your dog, avoid other medicines that can enhance the impact. If you’re unsure of the side effects of any medication your dog is currently on, you can contact your pet’s clinic and check to see if any of them depress the central nervous system. A few other side effects are:

  • an increase in saliva
  • vomiting
  • lethargy
  • trouble urinating
  • hyperactivity
  • impulsiveness
  • constipation 

Reasons to Use Zyrtec

Before giving your dog this medication, it is vital to ensure it won’t interact with any medicines your dog is currently on. If your dog has a history of renal or kidney problems, you need to talk to a vet before proceeding with a dose. Zyrtec can worsen the issues because it can cause urine retention in your dog. Exercise precaution if your dog has a history of sensitivities to antihistamines. Senior dogs and dogs under the age of one or any that have medical conditions should be ran by a vet. If in doubt about anything regarding your dog, call a vet. It’s always better to be extra safe when it comes to your doggy. Now that the scary details have been mentioned, there are a few reasons you may want to give your dog Zyrtec are:

  • Atopic dermatitis: This type of dermatitis is commonly caused by fleas, food, or direct contact with an irritant. It causes itchy skin that may cause the dog to scratch or lick excessively. This can cause the skin to become raw and agitated.
  • Urticaria: The better-known name for this is hives. It can be identified by welts in the skin being red and raised. Hives can appear anywhere on the dog’s body as well as in the mouth, ears, and eyes. While uncommon problems in dogs, hives can be caused by shampoos, medications, or chemicals.
  • Insect bites: Bug bites can lead to hives in dogs and allergic reactions ranging from mild to severe. The most common insect bites that occur in dogs are mites, ticks, fleas, bees, ants, and other similar bugs.
  • Itchy skin: This can be caused by some of the reasons previously listed above and infections.
  • Environmental allergens: Allergies can be caused by minor stuff such as mold, pollens, or dust. It often occurs due to seasonal changes.
dog with atopic dermatitis

Atopic Dermatitis may be one reason to give your dog Zyrtec.


Zyrtec Dosage and Instructions 

It is recommended to give your dog 0.5mg per pound of body weight. You can safely give Zyrtec to your dog up to 20 mg per day. It should only be administered orally. You can see a quick overview of dosages here:

  • 5 Ibs: 2.5 mg or ½ of a 5 mg tablet
  • 10 Ibs: 5 mg or 5 mg tablet 
  • 20 Ibs: 10 mg, one 10 mg tablet, or two 5 mg tablets
  • 50 to 100 Ibs: 20 mg or two 10 mg tablets 

If your dog doesn’t like taking capsules, there are a few things you can try. A pill dispenser, often called a pill popper, can help administer the pill to your dog. These look like syringes that let you place the tablet close to the back of the dog’s throat. It isn’t pretty, but it is effective. Pill pouches hide the pill, and the dog will eat them, thinking you are giving them a treat. The most common option is to sneak it into their food.  

Can You Give A Dog Benadryl for Allergies?

Veterinarian giving a Veterinarian giving a chihuaha a pilla pill

It’s important to consult with your vet before giving your dog any medication, like Benadryl.

© Tikhonova

While Zyrtec can be an excellent medication for your dog’s allergies, you may be wondering if there is an alternative you already have in your medicine cabinet. Benadryl, if given in a safe amount, can help dogs with allergies as well as motion sickness, anxiety, and vaccine side effects. When determining the dosage, give your dog 0.9-1.8 mg per pound of weight; a typical Benadryl capsule contains 25 mg. It is important to make sure the Benadryl is free of diphenhydramine, which can be harmful for dogs.

The photo featured at the top of this post is © Jus_Ol/

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About the Author

Creepy-crawly creatures enthrall Marisa. Aside from raising caterpillars, she has a collection of spiders as pets. The brown recluse is her favorite spider of all time. They're just misunderstood. You don't have to worry about squishing the creatures as her catching, and relocating abilities can safely move stray centipedes or snakes to a new location that's not your living room.

FAQs (Frequently Asked Questions) 

Is Zyrtec safe for pregnant and nursing dogs?

Despite the mild risks, it can be safe to take Zyrtec during a dog’s pregnancy. The drug is excreted through milk in lactating dogs and isn’t recommended.

Can an overdose of Zyrtec kill my dog?

If you suspect that your dog has taken more than the suggested dosage and are concerned that they have overdosed, you should promptly call a vet for assistance on what to do. Some versions of Zyrtec can have the ingredient pseudoephedrine, which can kill a small dog. The vet will give detailed instructions and may have you come in for emergency attention.

How long does it take for Zyrtec to work?

Generally, within an hour or so, you will see improvement, but it also depends on your dog’s symptoms—the more severe, the longer it may take to see results.

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