Cetirizine and Levocetirizine For Dogs: Safe Usage Guide

Allergies are common in dogs, with up to 10% of the canine population affected by some form of allergic disease. Allergies occur when the immune system overreacts to substances in the environment that are normally harmless. This leads to an inflammatory response causing symptoms like itchy skin, ear infections, sneezing, and watery eyes.

Antihistamines are a class of medication that can help provide relief from allergy symptoms in dogs. They work by blocking the effects of histamine, a chemical released by the body during an allergic reaction. Histamine is what causes many of the irritating symptoms associated with allergies. By preventing its effects, antihistamines can help control itchiness, swelling, mucus production, and other allergy issues.

The two most commonly used antihistamines for dogs are cetirizine and levocetirizine. Both are second-generation, non-sedating antihistamines that have proven effective in controlling allergy symptoms in canine patients. They are often recommended by veterinarians as a safe way to provide allergy relief for dogs. This article will discuss their usage, dosage, administration, side effects, interactions, and alternatives when treating dog allergies.

Cetirizine For Dogs
Cetirizine For Dogs

What is Cetirizine?

Cetirizine is an antihistamine drug used to treat allergic reactions in dogs. It works by blocking the effects of histamine, a chemical released by the body during an allergic reaction.

Some of the uses for cetirizine in dogs include:

  • Treating symptoms of allergies like itchy skin, hives, and inflammation
  • Controlling itching and scratching due to skin allergies
  • Managing allergic reactions to medications, vaccines, foods, or insect bites

Cetirizine is a second-generation antihistamine that is more selective and less sedating compared to first-generation antihistamines like diphenhydramine. It selectively blocks histamine H1 receptors that are responsible for allergy symptoms. This action prevents the release of other allergy chemicals in the body.

By inhibiting the effects of histamine, cetirizine provides relief from the common symptoms of allergies and allergic reactions in dogs like itching, sneezing, watery eyes, and runny nose. It starts working within 1-2 hours and provides relief for 24 hours with a single dose.

Levocetirizine For Dogs
Levocetirizine For Dogs

What is Levocetirizine?

Levocetirizine is a second-generation antihistamine that is closely related to cetirizine. The main difference is that levocetirizine contains only the left-handed isomer of cetirizine, while cetirizine is a racemic mixture of left and right-handed isomers.

Levocetirizine works by blocking histamine receptors and preventing histamine from attaching and activating these receptors. This inhibits the effects of histamine, which is responsible for allergy symptoms like itching, sneezing, and runny nose.

In dogs, levocetirizine is used for treating allergic skin conditions like atopic dermatitis. It helps provide relief from itching, swelling, and inflammation associated with allergies. Levocetirizine starts working within 1-2 hours after administration and provides relief for a full 24 hours.

Compared to cetirizine, levocetirizine has a higher affinity for histamine receptors and is twice as potent. It provides effective relief from allergy symptoms for dogs while causing less drowsiness.

Usage in Dogs

Cetirizine and levocetirizine are commonly used in dogs for treating allergy symptoms. Some specific conditions treated include:

– Seasonal allergies: Both medications can provide relief for dogs suffering from seasonal allergy symptoms like itchy skin, sneezing, watery eyes, etc. They help block histamine release which causes these allergy flare-ups.

– Atopic dermatitis: This condition causes itchy and irritated skin in dogs. Cetirizine and levocetirizine help provide anti-itch relief by inhibiting histamine reactions.

– Insect bite reactions: For dogs highly sensitive to flea, mosquito, or other insect bites, these antihistamines can soothe the itching and inflammation associated with the bites.

– Food allergies: Oral antihistamines like cetirizine and levocetirizine may be used short-term along with eliminating problem ingredients to control itching and hives caused by food allergies.

The key benefits of using cetirizine or levocetirizine for dog allergies include:

  • Provides fast-acting anti-itch relief
  • Reduces inflammation and skin irritation 
  • Controls allergy symptoms for improved comfort
  • Typically has mild side effects compared to other antihistamines
  • Low-cost oral medication

These second-generation antihistamines are commonly recommended by veterinarians for providing safe, effective relief for dogs with allergy symptoms. They are available both over-the-counter and through veterinary prescription. With proper dosing supervised by a vet, cetirizine and levocetirizine can significantly improve many dogs’ quality of life when dealing with allergies or atopic dermatitis.


The typical dosage range for cetirizine in dogs is 2-10 mg per day. Levocetirizine is usually given at 2.5-5 mg per day. These medications are typically given once daily.

The exact dosage will depend on the dog’s weight. Cetirizine doses between 2-4 mg per day are usually sufficient for small dogs under 10 lbs. Medium dogs 10-25 lbs can take 4-6 mg per day. Large dogs 25-90 lbs may need 6-10 mg per day.

For levocetirizine, typical dosages are:

  • Small dogs under 10 lbs: 1.25-2.5 mg once daily
  • Medium dogs 10-25 lbs: 2.5 mg once daily 
  • Large dogs over 25 lbs: 2.5-5 mg once daily

Your veterinarian will prescribe the appropriate dose for your dog based on weight, medical condition being treated, response to treatment, and other medications or supplements they may be taking. It’s important to follow your vet’s dosage recommendations.


Cetirizine and levocetirizine are available in different forms that can be administered to dogs:

– Tablets: Tablets can be given directly to the dog if they will swallow it willingly. Otherwise, the tablet can be hidden in food or treats. Be sure to check dosage requirements based on your dog’s weight before administering.

– Liquid: Liquid formulations can be administered directly into the dog’s mouth using a dropper or oral syringe. Dosage should be measured carefully based on the concentration of the liquid medication. Mixing the liquid into food or treats can help dogs take it more readily.

– Injection: In some cases, cetirizine or levocetirizine may be given by injection, typically by a veterinarian. This allows accurate dosing and absorption into the bloodstream.

Some tips for giving cetirizine or levocetirizine medication to dogs:

  • Give with food to reduce stomach upset. The medication may cause nausea or vomiting on an empty stomach.
  • Make sure your dog swallows the medication. Don’t let them spit it out.
  • Reward with a treat after giving the medication. This helps the dog have a positive association.
  • Avoid touching or handling the medication with your bare hands, as it can absorb into your skin. Use gloves or a clean utensil.
  • Shake liquid formulations well before drawing up the proper dosage amount.
  • Store the medication securely and out of your dog’s reach.
  • Keep track of when you give each dose to maintain the proper schedule.
  • Call your veterinarian if you have any difficulties or concerns about administering the medication.

Side Effects

Cetirizine and levocetirizine are generally well tolerated by dogs. However, some side effects may occur.

Common Side Effects

  • Drowsiness
  • Fatigue
  • Dry mouth
  • Loss of appetite
  • Vomiting
  • Diarrhea

These mild side effects often resolve on their own within a day or two as the dog’s body adjusts to the medication. Talk to your vet if any side effect concerns you or persists for more than a couple days.

Serious Side Effects 

More concerning side effects to watch for include:

  • Severe allergic reaction (trouble breathing, hives, swelling of the face/throat)
  • Agitation, restlessness, shaking, seizure
  • Fast/irregular heartbeat
  • Jaundice (yellowing eyes/gums)
  • Dark urine, clay-colored stools 
  • Easy bleeding and bruising

If you notice any of these signs, stop giving the medication and call your vet right away, as they can indicate a serious reaction requiring emergency care. It’s also important to let your vet know about any pre-existing conditions, as cetirizine/levocetirizine may worsen certain health problems.

Overall, side effects are uncommon if given as directed. Still, it’s important to monitor your dog after starting these medications and report any concerns promptly to your veterinarian.

Interactions With Other Medications

Some drugs and supplements can interact with cetirizine and levocetirizine, potentially causing increased side effects.

Drugs to Avoid

– Ketoconazole and other antifungal medications can increase the levels of cetirizine and levocetirizine in the body, enhancing their effects. These drugs should not be used together.

– Erythromycin and other macrolide antibiotics can also increase cetirizine and levocetirizine levels. Use caution when giving these medications concurrently.

– Theophylline can decrease the metabolism of cetirizine and levocetirizine, again increasing their effects. Combining these drugs is best avoided.

Supplements and Foods to Avoid

– Grapefruit juice can inhibit the metabolism of cetirizine and levocetirizine, boosting their effects and potentially causing toxicity. Do not give grapefruit juice to dogs taking these antihistamines.

– St. John’s Wort can increase the metabolism and clearance of cetirizine and levocetirizine from the body, making the antihistamines less effective. Avoid using this supplement together with cetirizine or levocetirizine.

– High fat meals can enhance the absorption of cetirizine and levocetirizine. It’s recommended to administer these medications on an empty stomach and avoid fatty foods around dosing times.


There are some alternatives to cetirizine and levocetirizine for treating allergies in dogs.

Other Antihistamines

– Diphenhydramine (Benadryl): This is an over-the-counter oral antihistamine that can be given to dogs. The dosage is 1-4 mg per pound every 6-8 hours.

– Hydroxyzine: This prescription antihistamine comes in both oral and topical forms. The dosage for oral hydroxyzine is 1-2 mg per pound every 12 hours. 

– Chlorpheniramine: This oral antihistamine is sometimes used for dogs. The dosage is 2-4 mg per dog 2-3 times a day.

Additional Treatment Options 

– Allergen-specific immunotherapy: This involves administering small amounts of an allergen to desensitize the dog’s immune system over time. It can be very effective but takes months.

– Omega-3 fatty acids: Supplements like fish oil can help reduce inflammation associated with allergies. Always consult your vet on dosage.

– Topical therapies: Hydrocortisone creams, ointments, and shampoos can provide relief for dogs with skin allergies. 

– Antibiotics and antifungals: May be prescribed by your vet for secondary skin infections associated with allergies.

– Allergen avoidance and minimizing exposure to triggers. Keeping the dog inside during high pollen times, using air filters, washing bedding frequently in hot water, etc.

Related: Ayurvedic Treatment For Dog Skin Allergy

End Notes,

Cetirizine and levocetirizine are prescription medications to treat allergies in dogs. Ensure you administer these drugs based on the directive of your vet. I hope this article gives a better guide on the usage and dosage of cetirizine and levocetirizine for dogs.

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