Zyrtec for Dogs: Dosage and Side Effects

Zyrtec for Dogs

Zyrtec with the active ingredient cetirizine is an antihistamine used to treat dermatitis, a condition that causes a dog’s skin to become itchy. Zyrtec is widely tolerated by dogs and has relatively few side effects.

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Does your dog suffer from hives or allergic itchiness?

An itchy dog is a danger to himself.

It is not unusual for an itchy dog to bite and chew so much that he makes the skin raw and sore.
This leads to double trouble because not only do you have the initial itchiness to deal with, but you have the extra problem of needing antibiotics for a skin infection.

What the owner of an itchy dog really needs is a medication that is widely available without a prescription, which doesn’t have the side effects of steroids, and yet may be able to help control that annoying skin irritation.

One product that can tick many of these boxes is Zyrtec for dogs.

What is Zyrtec for Dogs?

Zyrtec belongs to a family of medications called antihistamines.

You’re probably most familiar with these as a remedy for the sneezing, eye-watering nuisance that is hay fever in people.

Antihistamines work by inhibiting the effects of histamine, which is a substance released as part of the body’s immune defense system.

Whilst histamine has its place as increasing the supply of infection-fighting white cells to a trouble spot, it also unwanted properties such as causing redness, swelling…and itchiness!

Indeed, when you get bitten by a flea and your skin develops an angry red wheal that you can’t help but scratch, this is all down to histamine.

The dog equivalent of hay fever isn’t so much the respiratory signs that we people suffer from, but itchy skin.

dog melancolic

Zyrtec itself is a product containing the active ingredient cetirizine.

Now cetirizine isn’t just any old antihistamine, but a ‘second generation’ drug. This means it’s more sophisticated than the previous versions with the result that it has a more targeted action with fewer side effects.

Can I Give My Dog Zyrtec?

Yes, Zyrtec is considered a safe medication for your dog. The good news is that Zyrtec is widely tolerated by dogs and has relatively few side effects.

Indeed, the fact Zyrtec is second generation means that it lacks the sedative properties of other antihistamines, such as Benadryl (containing diphenhydramine, a first-generation antihistamine).
However, you should bear in mind that Zyrtec is a human medication and not licensed for use in dogs.

This means that although it is very safe, you give it on the understanding that it hasn’t been fully tested in canines and give the medication to your fur friend at your own risk.

big dog sad

Again, because it hasn’t been widely tested on dogs, it’s best to follow the guidelines set down for people.

In humans, it is not advisable for pregnant women to take Zyrtec as its effects on the fetus are not fully understood.

With this in mind its best not to give Zyrtec to pregnant female dogs or those feeding puppies.
Another important point to be aware of is that you must only give Zyrtec (cetirizine) and NOT a product that has other active constituents, such as Zyrtec D.

Is Zyrtec Safe for Dogs?

Be very careful which packet you pick up off the shelf, because whilst Zyrtec is safe for dogs, a similar product, Zyrtec D, is NOT.

This is because Zyrtec D contains the additional constituent, pseudoephedrine as a decongestant.
Pseudoephedrine is dangerous in dogs as it overstimulates the heart and central nervous system.

This can lead to dangerously high blood pressure, seizures, and ultimately death in some dogs.

dog dormant

The take-home message with regards to Zyrtec and safety is that you should always check and recheck the packaging to see what’s inside.

Only if you are 100% satisfied that it contains cetirizine only is it safe to consider.

What are the Side Effects of Zyrtec for Dogs?

All dogs are different, and just as one dog may be intolerant of beef in their diet, so some dogs may react badly to Zyrtec and drool heavily or vomit.

This is usually self-limiting and stops once the Zyrtec has cleared its way through the dog’s system.

Although Zyrtec is a non-drowsy formulation there is a possibility that a high dose, especially in a small dog, could lead to sedation and sleepiness.

puppy sleeping

This is most likely to happen when a small dog is given a higher dose than desirable because it’s difficult to break up a human tablet into small enough pieces.

However, this is rarely dangerous, and research indicates that a dog needs to take 95 times the recommended amount to reliably get symptoms of an overdose.

Why Would I Give My Dog Zyrtec?

Let’s say your dog has a big day ahead where you need him to be at his best.

Perhaps he’s taking part in a dog show or competing in an agility event.

However, he’s just been stung by a bee and you want to prevent him from breaking out in hives.

If you give him diphenhydramine, its side effect of sedation will make him groggy and take the edge off his performance.

sad dog staring

The answer is to go with a second-generation antihistamine and dose him with cetirizine in the form of Zyrtec.

One of the main reasons to give an antihistamine is allergic reactions.

This may either be because of an insect sting, which results in raised bumps on the skin and swelling of the affected area, or because of a skin allergy known as atopy.

Zyrtec and Atopy in Dogs

Atopy is extremely common in dogs.

If you have a dog that licks obsessively at his paws, turning white fur to a rust color, or he rubs his face or scratches, and especially if he seems worse at certain times of the year, then he may well be suffering from atopy.

This is an allergic reaction to allergens in the environment, this includes things like pollen and grasses (hence the seasonal element) along with dust mites and mold spores.

The dog’s immune system triggers a chain of events where it reacts inappropriately to the stimulus, resulting in itchy skin.

However a word of caution here because itchiness can be down to many factors.
For example a bacterial or yeast infection in the skin can cause intense itching (think athletes foot in people!).

Another major cause of itchiness is parasitic infections such as with fleas or mange mites, whilst dietary allergies are also infamous for producing skin signs.

focused dog

So be aware that itchiness is only a symptom and your vet will want to eliminate other possible causes before diagnosing atopy.

The vet can prescribe any of a number of anti-inflammatory drugs that can reduce itchiness, but these often need to be given in the long term, and whilst some are associated with unpleasant side affects others can be costly.

This makes the idea of an antihistamine that is easily available and relatively side effect free seems all the more appealing.

However, whilst antihistamines can help with insect stings, unfortunately, their effect can be disappointing when used against atopy.

Research indicates that their effectiveness against allergic itches is around 18%.

This means if you a cup half empty person you may be inclined to think you are wasting your money, whereas a cup half full person may think anything is worth a try.

Zyrtec Dosage for Dogs

When wondering: “How much Zyrtec can I give my dog?” there are two answers.

Generally, cetirizine is taken orally, in a tablet form, once a day. The required dosage some vets advised is mostly determined by your dog’s weight, with 0.5 mg of cetirizine per pound of your dog’s weight being the most commonly recommended dosage. (a small dog takes half a 10mg tablet, whilst a large dog takes a whole one.)

Atopic dose take Zyrtec once a day, whilst those who are stung by an insect can take it twice a day.
It doesn’t matter if Zyrtec is given on an empty stomach or with food, but for a speedier effect dose on an empty tummy since food in the stomach slows the absorption of cetirizine into the bloodstream.

And finally, know that if you have an itchy dog, especially if he’s just been stung by an insect, then Zyrtec can help reduce his discomfort and is unlikely to do harm.

However, the benefits in our fur friends tend to be disappointing as antihistamines are not as effective in four-leggers as they are in people.

dog on grass

By all means give Zyrtec a chance (check with your vet first) but be prepared to be disappointed by the result. Read our comprehensive guide on Dog Medication here. 

Dr Sarah Robinson attended veterinary school at Oklahoma State University receiving a D.V.M. in 2008. Sarah’s longtime interest is to help people to better communicate with their pet companions, and in doing so, to help them to strengthen their relationships with their dogs and cats. Sarah has published numerous articles on canine feeding in pet related magazines, veterinary journals and leading natural health web sites.

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