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Should you give your dog Zyrtec

The essentials

  • Zyrtec is an antihistamine — Like Benadryl or Claritin, Zyrtec may be used to alleviate mild allergy symptoms.  
  • Cetirizine is safe for dogs in low doses — Always ask your vet before giving your dog Zyrtec or any other medicine.
  • Side effects are rare — Vomiting, drooling, and sleepiness have been reported, but aren’t as likely to occur with cetirizine as they are with other antihistamines.

It should come as no surprise to most dog owners that our furry friends can be affected by allergies just like we are. Itchy skin, watery eyes, sneezing, and a runny nose are all possible symptoms of canine allergies. Zyrtec — or its active ingredient, cetirizine — may be used as an off-label medicine in low doses to manage these symptoms.

How is Zyrtec used for dogs?

Zyrtec is a brand of over-the-counter allergy medication. It contains an antihistamine called cetirizine, which is typically used for human allergy symptoms. Cetirizine blocks the natural substances called histamines that the body produces when it experiences an allergic reaction. 

While it isn’t FDA-approved for use in animals, Zyrtec has become a popular off-label drug for dogs suffering from allergies. It’s a popular option for dog owners because it doesn’t cause drowsiness as often as Benadryl.   

With their vet’s approval, pet parents may give their dog Zyrtec to help with things like: 

Mild allergy symptoms may be treated at home, but severe allergic reactions require immediate veterinary care. Watch out for signs of an anaphylactic reaction , such as pale gums, shaking, swelling, vomiting, and diarrhea.

🚨 While regular Zyrtec is okay, never give your dog Zyrtec-D. Zyrtec-D contains the active ingredient pseudoephedrine. This drug is very dangerous to dogs, possibly leading to high blood pressure, seizures, and even death.

Zyrtec dosage for dogs

Proper dosing can vary based on your dog’s body weight and symptoms. You should never give your dog more than 20 mg at once, but small dogs have a much lower limit. Giving your dog too high of a dosage can actually worsen symptoms or lead to harmful side effects.  

While you should consult your veterinarian before giving your dog any medicine, here’s a breakdown of general dosage guidelines based on your dog’s weight, which is generally calculated at 1 mg/kg every 12-24 hours:

Cetirizine dosage chart for dogs

Dog Size Dosage Breed Example
5 lb. 2.5 mg, or 1/2 of a 5 mg tablet Chihuahua
10 lb. Up to 5 milligrams Maltese
30 lb. Up to 15 milligrams Cocker Spaniel
50 lb. Up to 20 milligrams Siberian Husky
100 lb. Up to 20 milligrams Great Pyrenees

While Zyrtec is considered generally safe, it can be dangerous for dogs with certain medical problems, such as kidney disease. Always ask your vet first and make sure they’re aware of all of your dog’s medications to avoid possible drug interactions.  

Side effects of Zyrtec (cetirizine) for dogs

While Zyrtec doesn’t usually cause any adverse side effects, every medicine comes with precautions when deciding whether they’re the best treatment. Research shows that antihistamines only work in about 30% of cases. 

Also, antihistamines aren’t a cure but a temporary fix that doesn’t address the underlying cause. Zyrtec can also cause additional issues for dogs with kidney problems and liver problems.

Although adverse reactions seem to be rare, the most common side effect of Zyrtec is sleepiness. Others may include:

  • Constipation
  • Vomiting
  • Urine retention
  • Impulsive responses (they might be more irritable or reactive than normal)
  • Excessive salivation

Alternatives to cetirizine for dogs

If Zyrtec isn’t a good fit for your dog, ask your veterinarian about one of these alternative antihistamines or allergy treatments: 

Diphenhydramine (Benadryl)

You can give your dog up to 1 milligram of diphenhydramine per pound of body weight 2 to 3 times daily. Benadryl is a popular antihistamine often used as a mild relaxant or sedative, although it’s not recommended for that use and doesn’t always have that effect . However, compared to cetirizine, there’s a greater risk of drowsiness.

Loratadine (Claritin)

With your vet’s approval, you can give your dog ¼ milligrams of loratadine per pound of body weight once a day. Just make sure you choose Claritin or the store-brand equivalent that only contains loratadine — no pseudoephedrine or other decongestants that are toxic to dogs.

Prescription drugs

Your vet may choose to prescribe Apoquel or Atopica tablets, or steroid or Cytopoint injections to try to reduce your dog’s allergy symptoms. These prescription allergy medications are more effective than over-the-counter options and may be a good idea for dogs with chronic symptoms. 

If your dog experiences a flareup of symptoms that result in an ear infection or hot spots on their skin, your vet will also give you medicine to treat the infection.

Fish oil

Fish oil is full of omega-3 and omega-6 fatty acids. These compounds reduce inflammation, which can reduce allergy symptoms. Check out our fish oil guide for more benefits and recommended dosages. 

Just like in humans, dog allergies are common but difficult to diagnose. If your dog seems excessively itchy or sneezes or coughs frequently, you should always take them to the vet first to receive the most accurate answers about the cause of their ailments and information on possible treatments. While Zyrtec is generally safe for dogs, it’s important to choose a type that doesn’t contain any other medications, such as decongestants, that can be toxic.

Frequently asked questions

Can I give my dog 10 mg of Zyrtec? 

As long as your vet says it’s okay, it should be fine.  The actual amount might be more or less depending on their weight. If your dog weighs at least 20 pounds, you may be able to give them a standard 10-milligram Zyrtec tablet. If your dog weighs less than 20 pounds, you’ll likely need to invest in a pill cutter to give them the correct amount. 

Can I give my dog Zyrtec instead of Apoquel?

Yes. As a prescription-only antihistamine, Apoquel is actually more effective at relieving itchy skin caused by allergies. According to this 2022 study, Cytopoint injections are even better. 

Can my dog take Zyrtec every day?

A 2016 study found that dogs with allergy-related dermatitis stopped improving after 14 days of taking cetirizine. Based on the findings, Zyrtec should only be given to combat short-term allergy symptoms, such as a flare–up after being outside all day, instead of administered as a long-term solution. 

What is the difference between Zyrtec and Benadryl for dogs?

Both Zyrtec and Benadryl are antihistamines that function very similarly. The only thing you have to worry about with Zyrtec is making sure you choose a medication that only contains cetirizine. Some combinations of cetirizine medications also contain decongestants that are toxic to dogs. 

You should also never give your dog two different allergy medications at once. Always ask your vet before giving your dog any new medicine — especially if they’re already taking medications that could cause a drug interaction.  

Can puppies take Zyrtec?

Dr. Liza Cahn states, “While it is probably safe to give Zyrtec to a puppy over 12 weeks of age, you should consult with your veterinarian first. Most dogs develop environmental allergies between 6 months and 3 years of age, so if a young puppy is showing concerning symptoms it’s best to take them to the vet.”