Search for articles or Rx savings
Key takeaways
Zyrtec (cetirizine) is an antihistamine typically safe to give to dogs, but Zyrtec-D is not.
Zyrtec begins relieving allergy symptoms, like skin reactions and itching, within an hour of ingestion.
Zyrtec’s therapeutic effects should last up to 24 hours, but some veterinarians may prescribe one dose every 12 hours.
Canine companions instinctively enjoy outdoor activities, but allergies can dampen their fun. When that happens, pet caregivers can use Zyrtec (cetirizine) to help their dog. A dose of Zyrtec can start relieving allergy symptoms in about an hour, and the effects will probably last the entire day. Zyrtec is safe for dogs, but consult a veterinarian before giving a pet Zyrtec tablets.
Save up to 80% on Zyrtec with SingleCare
Different pharmacies offer different prices for the same medication. SingleCare helps find the best price for you.
RELATED: Discount pet meds & resources
Can I give my dog Zyrtec?
Standard Zyrtec, with no decongestants, can be given to dogs. Veterinarians typically prescribe it for allergic skin reactions and itchy skin. Theoretically, cetirizine can relieve most mild canine allergy symptoms, such as a runny nose, sneezing, and airway inflammation, but vets primarily use it for skin reactions.
“It’s important to note that dog allergies can range in severity,” says Dr. Jessica Apted, DVM, the regional medical director at Sploot Veterinary Care. “Generally, dogs have manageable allergic reactions that can be treated with lifestyle changes, dietary prescriptions, and medications like antihistamines. However, if an allergy escalates to life-threatening anaphylaxis, antihistamines like Zyrtec are not effective.”
She also explains that “Zyrtec’s use for dogs is ‘off-label.'” This means that proper vet guidance and consultation are necessary for safe use. Talk to your dog’s vet before administering Zyrtec or other drugs.
Important Note: While standard Zyrtec is safe for dogs, never give a dog Zyrtec-D. The “D” in its name stands for decongestant. For Zyrtec-D, the decongestant added to the tablet is pseudoephedrine, which is toxic for dogs. Check the drug’s packaging and label carefully before giving it to your pet.
RELATED: Allergy medicine coupons & resources
How quickly does Zyrtec work in dogs?
In people, Zyrtec reaches peak concentrations in about an hour, so expect Zyrtec for dogs to start relieving symptoms within that time. Of course, Dr. Apted adds, Zyrtec’s efficiency can vary depending on the dog, the dosage, underlying conditions, gastrointestinal issues, the dog’s metabolism, and other medications the dog is taking.
Zyrtec for dogs works the same way it does in humans: blocking histamines, chemicals produced by the immune system in response to allergens like pollen, dust, or mold. Allergy symptoms, like itching and swelling, are caused by histamines to aid the body’s effort to fight off the foreign substance.
In dogs, the terminal half-life of cetirizine is about 10 to 11 hours, slightly longer than in people (about 8 hours). However, the antihistaminic effects last for 24 hours in people, so that’s what veterinarians expect in dogs. However, a vet may prescribe one dose or two doses of cetirizine daily, so it’s important to give a dog cetirizine only under the direction of a vet.
Benefits of Zyrtec for dogs
It’s no use giving a dog Zyrtec unless it can provide some allergy relief. Fortunately, it can handle a wide range of them. For example, a 2020 study found that Zyrtec “significantly reduced histamine,” suggesting it may treat other symptoms of seasonal allergies, insect bites, and other allergic reactions.
However, Zyrtec might not be as effective for chronic atopic dermatitis (atopy), a condition involving severe itching and skin redness. One 2016 study concluded that it performed about the same as a placebo in treating the condition, and an older study showed it reduced atopic dermatitis symptoms in only 18% of dogs. It may or may not be the best option if your dog has chronically itchy skin.
The good news is that second-generation antihistamines like Zyrtec and Claritin (loratadine) don’t cross the blood-brain barrier, which means they’re less sedating than first-generation antihistamines like Benadryl (diphenhydramine) or hydroxyzine.
Second-generation antihistamines like Zyrtec are less likely to have serious drug interactions than first-generation ones, so Zyrtec may be safer to take with other medications.
Side effects of Zyrtec in dogs
Even though newer antihistamines like Zyrtec pose less of a risk for serious side effects, they may still cause milder ones, including:
- Drowsiness
- Excessive salivation
- Vomiting
There are currently no reported serious side effects in dogs. But it’s still crucial to administer it in appropriate doses and follow the veterinarian’s instructions.
Dogs allergic to cetirizine shouldn’t take it since it may cause a severe allergic reaction. In a dog with kidney or liver disease, consult a vet before administering Zyrtec.
There’s very little data on Zyrtec for pregnant or nursing dogs, so talk to the veterinarian.
“If Zyrtec is given an appropriate dose, it can be safe for most dogs, but there are contraindications if combined with other medications,” says Dr. Dwight Alleyne, DVM, a veterinarian adviser at Betterpet. Specifically, Zyrtec can interact with opioids, anxiety medications, sleep aids, muscle relaxants, central nervous system depressants, and other antihistamines. So, play it safe and inform the veterinarian about any medications or supplements the dog is taking.
RELATED: Zyrtec side effects and how to avoid them
Dosage of Zyrtec for dogs
Giving a dog the correct dosage is critical for Zyrtec’s effectiveness and safety. But since dogs vary widely in size, the recommended Zyrtec dosage for dogs is based on the dog’s weight, typically 1 mg per kilogram of body weight, given once every 12 or 24 hours. That translates to about one milligram for every two pounds of body weight, so a 20-pound dog might be prescribed a 10 mg Zyrtec tablet.
Zyrtec comes as 5 mg and 10 mg tablets or chewable tablets. To make it easier, veterinarians may prescribe 1/2, 1, or 2 tablets per dose. Doses usually max out at 20 milligrams, as they do for people.
Yet certain factors can influence that dosage. It “depends on the dog’s health condition, age, weight, and the severity of the dog’s allergy symptoms,” Dr. Apted says. “It’s crucial to consult a veterinarian before administering Zyrtec to ensure the correct dosage and to rule out any potential contraindications or interactions.”
Zyrtec is fine for dogs to take with or without food. However, if the dog vomits after taking the medicine, give it with food.
If you miss a dose, don’t give the dog a double dose to compensate for it. Instead, just provide the next dose as you normally would.
Zyrtec is often a short-term treatment until the allergy symptoms subside, but it is also safe to take long-term if the dog needs it. However, that’s up to the veterinarian, and you should always follow their instructions about how and when to administer Zyrtec.
RELATED: Cetirizine for dogs: dosage and safety of generic Zyrtec
- Antihistamines: if/when are first generation medications advantageous over newer antihistamines?, American Academy of Allergy, Asthma, & Immunology (2021)
- Cetirizine hydrochloride (Zyrtec), Veterinary Partner (2023)
- Effect of diphenhydramine and cetirizine on immediate and late-phase cutaneous allergic reactions in healthy dogs: A randomized, double-blinded crossover study, Veterinary Dermatology (2020)
- Effects of cetirizine in dogs with chronic atopic dermatitis: a randomized, double blind, placebo-controlled trial, Journal of Veterinary Science (2016)
- Plumb’s Veterinary Drug Handbook, 7th ed (2011)
- Pseudoephedrine toxicity in pets, ASPCA
- Saunder’s Handbook of Veterinary Drugs 4th ed. (2016)
- Treatment of canine atopic dermatitis with cetirizine, a second generation antihistamine: a single-blinded, placebo-controlled study, The Canadian Veterinary Journal (2004)