Zyrtec for Cats: Dosage, Uses, Side Effects (Vet Answer)

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Allergies in cats can have symptoms similar to those in us: watery eyes, runny nose, mild nasal congestion, and sometimes coughing. More often, cat allergies manifest as itching, redness, and/or swelling of the skin.

The brand name Zyrtec may sound familiar. This is a common over-the-counter (OTC) allergy medication that many of us take in the midst of pollen season. But can Zyrtec be given to cats? Yes, you can give Zyrtec to cats, but it is important to consult your veterinarian before giving Zyrtec to your cat. This article explains what Zyrtec is, if and how you can give it to your cat, and the side effects your cat may experience.

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What is Zyrtec?

Zyrtec is the brand name for the drug cetirizine HCL (cetirizine hydrochloride). Zyrtec is an antihistamine allergy medication. When a cat’s body reacts to an irritant or allergen, histamine is released. This is a naturally occurring substance and can be released without issue. In allergies and allergic reactions, excess histamine can cause itching, redness, and sometimes swelling. Antihistamines work by blocking histamine from binding to specific cell receptors and causing the effects mentioned above. Zyrtec belongs to the class of antihistamines classified as H-1 blockers.

Veterinarian gives deworming medication to cat
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How is Zyrtec given to cats?

Zyrtec is administered orally. If your veterinarian recommends giving her an OTC product, it can come as tablets, chewable tablets, gel caps, or pediatric liquid milk. Gelcaps may not be recommended given the dosage required for cats. If you have difficulty giving your cat medication, your veterinarian may be able to prescribe medication for you. This means that compounding pharmacies can also make and flavor the drug in a different form than what is available OTC.

Zyrtec is given to cats every 12 to 24 hours or once or twice a day. Giving cats medication can be very difficult, but it doesn’t have to be given with food. It may be much easier to give it to your cat mixed in with their food, as it will be easier for your cat to eat treats such as tuna. Giving Zyrtec with or without food does not change its effectiveness.

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Zyrtec dosage for cats

It’s important to know your cat’s current weight. Depending on the cat’s weight, the dose of cetirizine is 1 mg of Zyrtec per kilogram of the cat’s weight. Typically, this totals 2.5 mg to 5 mg. However, be sure to check with your veterinarian, as they may recommend a different dosage.

Devon rex cat takes medicine
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What happens if I forget to take a dose?

The best part is that there are no serious side effects if you do not administer the dose or do not allow your cat to give it the medicine. Zyrtec is not a drug that needs to be dosed in order to be effective in cats.

It is worth noting that serious allergies in cats are often not affected by over-the-counter antihistamines. In other words, if your cat has severe allergies, you won’t see any improvement in your allergy symptoms. If you are regularly giving your cat the recommended dose of Zyrtec and both you and your veterinarian do not notice any improvement in your cat’s allergy symptoms, it may not be effective for your cat. At that point, you should discuss other options with your veterinarian.

Potential side effects of Zyrtec in cats

In general, cats can be very stubborn and dramatic when taking medications. Zyrtec does not have any common side effects, but some cats may spit, drool, foam at the mouth, and exhibit dramatic symptoms simply because they are given the drug.

Mild drowsiness may occur, especially in smaller cats, but does not always occur.

If your cat has underlying liver or kidney disease, your veterinarian may recommend a lower and/or smaller dose. This is because if your cat has pre-existing conditions, it may take longer for the medication to process.

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Is it okay to give Zyrtec D to cats?

no! This is extremely harmful to cats and can even lead to death. The “D” in the name stands for decongestant, and this formula contains the drug pseudoephedrine. Pseudoephedrine is extremely toxic to dogs and cats and can be extremely fatal. Never give your cat or dog any medication containing pseudoephedrine unless specifically prescribed by your veterinarian.

Is Zyrtec effective?

Zyrtec is effective for mild pruritus (itching) in cats. However, for severe underlying allergies, over-the-counter medications are often not sufficient. Your cat may need a new diet, proper flea preventive medication, prescribed allergy medication, or steroids to stop the itching completely.



Allergies in cats are most commonly seen as itchy skin. Over-the-counter antihistamines may help relieve some of the most common symptoms of allergies. Zyrtec is one of the over-the-counter medications that can be commonly administered. It is sold as an oral formulation and should be administered based on your cat’s current weight and your veterinarian’s recommendations based on that weight.

Zyrtec is administered as an oral medication in tablet or liquid form. Alternatively, your veterinarian may have a pharmacy make the medication in a different form. There are few side effects other than occasional drowsiness. It is important to never give Zyrtec-D to cats. Also, be aware that over-the-counter antihistamines may not be effective. Always work with your veterinarian to get the best recommendations.

Featured image credit: David J Garcia, Shutterstock

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