Zyrtec for cats: Dosage and safety

In this article:

• Uses
• Safety
• Dosage
• Alternatives
• Summary

In this article

• Uses
• Safety
• Dosage
• Alternatives
• Summary

Zyrtec is a brand-name nonprescription allergy medication. Its active ingredient, cetirizine, is a second-generation antihistamine. People use Zyrtec to relieve seasonal allergy symptoms such as sneezing, a runny nose, and watery eyes. Veterinarians may also recommend Zyrtec for cat allergies, particularly to help relieve allergy-related itching. Less commonly, cetirizine may be used for certain respiratory allergy symptoms in cats. Although side effects are generally mild, its use in animals is “off-label.” 

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What is Zyrtec used for in cats?

Zyrtec, or generic cetirizine, may help relieve itchy skin (pruritus) in cats caused by skin allergies, hives, or insect bites. However, antihistamines are not consistently effective at treating pruritus in cats, so they’re generally not considered a first-line treatment. Cetirizine may also be used for respiratory allergy symptoms in cats. Cetirizine is also a suggested but unproven therapy for chronic inflammation of the sinuses and nasal passages in cats. 

Itchy skin

Itchy skin is common in cats and can have several causes, including allergic reactions, food allergies, flea bites, and insect bites. Feline atopic skin syndrome (FASS), an itchy skin condition related to environmental allergies, is one of the most prevalent skin diseases in cats. 

Histamine is one of the chemicals involved in allergic reactions. When histamine binds to certain receptors, it can contribute to inflammation and itching. Zyrtec blocks H1 histamine receptors, reducing histamine’s effects. 

However, antihistamines are generally less effective at relieving itchiness in cats than they are in people. For this reason, Zyrtec and other antihistamines may not provide enough relief when used alone. 

The common treatment for itchy skin in cats is corticosteroids such as prednisolone or dexamethasone. Because prolonged corticosteroid use can cause significant side effects, veterinarians may use antihistamines as an add-on treatment alongside other therapies. 

RELATED: Stop the itch: How to treat allergies in cats and dogs 

Chronic rhinosinusitis (CRS)

Rhinosinusitis is inflammation of the nasal passages (rhinitis) and sinuses (sinusitis). In cats, chronic rhinosinusitis is characterized by persistent or recurrent nasal discharge and sneezing without an identifiable underlying cause. Cats that have previously had a respiratory viral infection may be at greater risk of developing chronic rhinosinusitis.

Veterinarians are unsure of the cause of chronic rhinosinusitis in cats, but it frequently develops after a severe viral respiratory infection. Over time, damage to tissues in the nose and sinuses can interfere with the nose’s ability to filter debris and microorganisms. The damage may also make cats more vulnerable to repeated secondary bacterial infections, contributing to recurring nasal discharge and sneezing. 

Chronic rhinosinusitis can be difficult to treat and is usually managed rather than cured. Veterinarians may prescribe antibiotics when a secondary bacterial infection is present or suspected. Other treatments that may help include corticosteroids, nasal lavage, humidification, L-lysine, and second-generation antihistamines such as Zyrtec. However, these additional treatments have not been scientifically evaluated specifically for chronic rhinosinusitis, and their effectiveness can vary. 

Is Zyrtec safe for cats?

Cetirizine for cats is generally well tolerated when used as directed by a veterinarian, although it may not be very effective for relieving itching. Cats with hypersensitivity to cetirizine or a similar drug called hydroxyzine should not be given Zyrtec. 

Never give a cat Zyrtec-D, a drug that combines cetirizine with pseudoephedrine, a decongestant. Over-the-counter medications containing pseudoephedrine or phenylephrine can be toxic to pets. Even small amounts may be toxic, potentially causing high blood pressure and a fast heart rate. 

Side effects of Zyrtec in cats

Zyrtec side effects in cats are uncommon. Possible side effects include:

• Sleepiness, particularly at higher doses
• Vomiting
• Increased salivation

No serious side effects have been reported in pets taking cetirizine. 

Interactions of Zyrtec with other pet meds

Do not give a cat Zyrtec without talking to a veterinarian. Tell the veterinarian about all the drugs, remedies, vitamins, and supplements the cat receives. 

Cetirizine may increase drowsiness when combined with other medications that cause sedation, including opioids, benzodiazepines, and Cannabinoids such as CBD.

Zyrtec can also interfere with allergy skin testing. Antihistamines may need to be stopped before an intradermal allergy test, so ask the veterinarian how long before testing to discontinue cetirizine. Some veterinary guidance recommends stopping antihistamines for at least one week, although recommendations can vary. 

Zyrtec dosage for cats

Several cetirizine dosages are recommended for cats, so dosages may vary between veterinary professionals. Plumb’s Veterinary Drug Manual suggests the following dosages:

• For itchy skin: 2.5–5 mg once per day
• For non-responsive chronic rhinosinusitis: 5 mg once or twice per day

The American Animal Hospital Association recommends a dosage of 5–10 mg per day for itchy skin. The Merck Veterinary Manual suggests a dose of 1 mg/kg, or a total of 5 mg, given once or twice daily.

Can cats overdose on Zyrtec?

Do not give a cat more Zyrtec than recommended by a veterinarian. If a cat is given too much Zyrtec, call a veterinarian for advice. If a veterinarian cannot be reached, consider taking the cat to an emergency animal hospital. High doses of cetirizine may cause neurological effects. Depression and hyperactivity are among the most commonly reported effects of overdoses involving antihistamines in the same drug class, and seizures may occur at higher doses. 

If a cat is given Zyrtec-D, seek veterinary care immediately. Zyrtec-D contains pseudoephedrine, which can cause serious or even life-threatening toxicity in pets. Symptoms can include hyperactivity, agitation, dilated pupils, vomiting, increased salivation, rapid heartbeat, high blood pressure, tremors, and seizures. 

Can I give my cat Zyrtec every day?

When prescribed by a veterinarian, Zyrtec can be given to a cat daily as directed. It may not be effective for every cat, but antihistamines may sometimes be used alongside corticosteroids and other treatments for itchy skin. 

How to give your cat Zyrtec

Zyrtec comes in several formulations, including tablets, chewable tablets, orally disintegrating tablets, and liquid. The appropriate formulation and dose will depend on the veterinarian’s instructions. Children’s Zyrtec Allergy syrup contains 1 mg/mL of cetirizine, while Children’s Zyrtec chewable tablets are available in a 2.5 mg strength. A veterinarian may also prescribe cetirizine from a compounding pharmacy when a different strength or formulation is needed. 

To ensure safety and effectiveness, here are a few pointers:

• Do not give a cat Zyrtec or generic cetirizine except under the direction of a veterinarian.
• Follow all the veterinarian’s instructions. 
• Cats can take cetirizine with or without food. If the cat vomits or seems unwell after taking it, try giving the next dose with a small amount of food. 
• If you’re not experienced at giving pills to a cat, ask a veterinary professional to demonstrate the proper technique. The veterinarian may suggest a pill plunger, but get a demonstration before using one.
• If giving an oral syrup or solution, measure each dose carefully with an appropriate dosing device and follow the product label for instructions, such as whether the liquid needs to be shaken. 
• Ask the veterinarian whether Zyrtec chewable tablets are appropriate for your cat. 
• What to do if a dose is missed depends on the dosing schedule. 
  • For twice-daily dosing, skip the missed dose and give the next dose at the scheduled time.
  • For once-daily dosing, give the missed dose when remembered unless it is almost time for the next dose. In that case, skip it and resume the regular schedule.
  • Do not give two doses at once.
• There is no need to taper the dose when discontinuing Zyrtec.

Zyrtec alternatives for cats

Antihistamines may provide limited relief for itchy skin in cats and may be most useful when itchiness is mild. Their effectiveness for chronic rhinosinusitis is less certain, although second-generation antihistamines such as cetirizine may help some cats.

For more persistent or severe itchy skin, other treatments veterinarians may use include: 

• Corticosteroids such as prednisolone
• Immunosuppressants such as cyclosporine or oclacitinib
• Allergen-specific immunotherapy
• Essential fatty acids
• Maropitant

Zyrtec may sometimes be used alongside corticosteroids and could allow the corticosteroid dose to be reduced. If a cat can’t take cetirizine, alternative antihistamines include: 

• Hydroxyzine
• Chlorpheniramine
• Cyproheptadine
• Clemastine
• Loratadine 
• Fexofenadine
• Amitriptyline, an antidepressant that is also a pain and itch medication, is also an antihistamine more powerful than Benadryl (diphenhydramine)
• Diphenhydramine

Antibiotics are the preferred treatment for chronic rhinosinusitis. Other treatments, such as antihistamines, are unproven or only sometimes successful.

Summary

Zyrtec and its generic version, cetirizine, are generally well tolerated in cats when used as directed by a veterinarian, but they may provide only limited relief for itchy skin. Cetirizine has also been suggested for chronic rhinosinusitis, although its effectiveness for this condition has not been well established. Veterinarians may use antihistamines alone for mild itching or alongside other treatments in more persistent cases. Zyrtec-D contains pseudoephedrine, which can cause serious or life-threatening toxicity in cats and should not be given to them.