Like their owners, every dog experiences the occasional itchy skin. In some cases, though, that occasional itch becomes a recurring issue. Chronic itching can have several causes, the most common being allergic skin disease.

Canine allergies can be challenging to manage. Vets and pet owners often turn to a dog allergy medicines for relief, including antihistamines like Zyrtec. But is it safe dogs?

What is Zyrtec?

Zyrtec, also known by the generic name cetirizine, is a second-generation antihistamine. It was developed in the 1980’s, with the goal of treating allergy symptoms while minimizing some of the side effects associated with Benadryl (diphenhydramine) and other first-generation antihistamines.

Zyrtec is FDA-approved for use in humans only. But it’s used “off-label” as an allergy medicine for dogs. While the manufacturer of Zyrtec hasn’t pursued FDA approval for its use in dogs, veterinarians have prescribed Zyrtec to their patients for many years. Its use has been studied both in veterinary patients and in the laboratory environment.

You can buy Zyrtec at any human drugstore, and the generic version may also be available through your vet. Be sure to talk to a veterinarian before using to get specific dosing recommendations for your dog.

What Does Zyrtec Look Like?

Zyrtec for dog allergies usually comes as a white, uncoated tablet. You may also find it as a colorless to pale yellow liquid suspension. Most veterinarians recommend tablets for large dogs and the liquid for small dogs.

Zyrtec is also available as a chewable children’s tablet. However, it’s best to avoid the chewable version of Zyrtec for dogs. Some flavors and formulations may contain xylitol, an artificial sweetener that is toxic to dogs.

Liquid-filled capsules are also available, but these are larger than tablets and therefore less convenient for dogs.

Is Zyrtec Safe for Dogs?

Zyrtec, or cetirizine, is generally regarded as a safe medication for most dogs. Significant side effects are rare in healthy dogs given appropriate doses. When side effects do occur, they tend to be minimal.

But not every dog is a good candidate for Zyrtec. Always talk to your veterinarian before giving your dog Zyrtec or any other over-the-counter medication. Your veterinarian is familiar with your dog’s medical history and risk factors. They can make the best medication recommendations for your individual dog.

Combination products containing Zyrtec can be highly toxic to dogs. For example, Zyrtec-D combines Zyrtec and a decongestant. Decongestants have several serious side effects in dogs and can even be fatal. Zyrtec-D is NOT safe for dogs.

How Does It Work?

Zyrtec is an antihistamine. It blocks histamine, a chemical substance produced during an allergic reaction. Histamine causes many of the effects we associate with allergies in dogs, such as itching and skin inflammation.

Zyrtec blocks the receptors on which histamine acts. This minimizes the impacts of histamine, reducing itching, inflammation, and other signs of allergies.  

What Is Zyrtec Used For in Dogs?

Zyrtec is an allergy medicine for dogs. It is frequently used to treat skin itching and inflammation associated with atopic dermatitis, a condition caused by a reaction to inhaled allergens. Zyrtec can also be used to treat other allergic reactions, including insect bites and stings and hives.

Common applications for Zyrtec in dogs include:

• Atopic dermatitis (atopy)
• Insect bites and stings
• Hives

Your veterinarian may also recommend Zyrtec to treat other allergic conditions. If Zyrtec doesn’t help, your veterinarian can recommend other appropriate treatments and testing.

What Symptoms Does Zyrtec Address?

Allergies in dogs manifest in many ways. These include scratching and itching, sneezing, coughing, hives, skin infections, ear infections, and more. They can be acute reactions to certain irritants or seasonal allergies. Pet insurance can help cover the costs associated with testing and treatment. Consider a plan to help manage costs in diagnosing and treating your dog with allergies.

How to Give This Medication to Dogs

Zyrtec is usually given as a flavorless tablet or a liquid medication. In its generic form, cetirizine may be available as compounded liquid medication in a variety of flavors from your veterinarian. Zyrtec is given once daily and with or without food.

Side Effects of Zyrtec for Dogs

Zyrtec is typically associated with minimal side effects in dogs. It’s less likely to cause sedation than other antihistamines, though drowsiness may occur at high doses. In contrast, some dogs become more excitable after taking Zyrtec.

Gastrointestinal effects, like vomiting and diarrhea, may occur but are also relatively uncommon. You may also notice decreased appetite and increased salivation, which may indicate nausea.

Side effects to watch for with Zyrtec include:

• Drowsiness
• Hyperexcitability
• Vomiting
• Nausea
• Increased salivation
• Decreased appetite
• Diarrhea

If you see any of these side effects, stop giving Zyrtec and contact your veterinarian. Fortunately, side effects associated with Zyrtec should wear off within approximately 24 hours.

Dogs with the following conditions may be at higher risk of side effects from Zyrtec:

• Seizure disorder
• Glaucoma
• Urinary issues
• Constipation
• Pregnancy
• Nursing mothers

If your dog has one of these conditions, avoid giving Zyrtec unless it is under the guidance of your veterinarian.

Avoid Zyrtec-D or any other formulations that may contain a decongestant. Pseudoephedrine, a common decongestant in human medications, is highly toxic to dogs.

Reactions With Other Drugs and Medications

Cetirizine can interact with a number of commonly-used veterinary drugs, including:

• Digoxin
• Selegiline
• Amitraz
• Ketoconazole
• Fluconazole
• Azithromycin.

Zyrtec can also worsen the drowsiness caused by sedatives and anxiety medications.

Talk to your veterinarian before combining cetirizine with any other prescription or over-the-counter medications.

Zyrtec Dosage for Dogs

Dosage depends on your dog’s body weight, the severity of your dog’s allergies, and your dog’s expected susceptibility to side effects. The following chart serves as general guidelines for dosage, but you should always consult your veterinarian first.

Dog’s Weight (in lbs)	Tablet Dosage	Max Dosage (per day)*
5	2.5mg	2.5mg
10	5mg	5mg
15	7.5mg	7.5mg
20+	10-20mg	20mg

Zyrtec is usually given once daily.

Cost of Zyrtec for Dogs

Zyrtec is an inexpensive medication, especially when purchased in its generic version (cetirizine). In general, you can expect to spend less than $30 per month for your dog’s cetirizine.

Zyrtec Storage Instructions

Zyrtec tablets and liquid suspension do not need refrigeration.

Zyrtec can be stored at room temperature, on a counter or in a medicine cabinet.