Ultimate Dog

By Sara Seitz - Reading Time: 12 minutes
dog allergies

Piriton for Dogs: Uses, Risks, and Natural Alternatives

During my time as a dog trainer, I encountered countless dogs with debilitating allergies. Constant scratching, head shaking, and rubbing up on anything they could find made training a challenge and left their owners stressed about more than their dog's obedience skills. Desperate for relief, many of these owners turned to Piriton.

While this drug usually provided some relief to dogs suffering from allergies, the effects were always incomplete and short-lived. Once a dose was missed, the dog was back to scratching itself raw. Worse still, Piriton did nothing to address the cause of the allergies.

This left many of my clients asking me if there was a better option out there. For most, luckily, the answer was yes!

Below, we’ll look at Piriton use in dogs, including how it works, its strengths, weaknesses, and potential side effects. Then we’ll discuss some natural alternatives to Piriton that can help treat the cause of your dog’s allergies to help them find complete and lasting relief.

Piriton Use in Dogs

When dogs experience allergic reactions, they typically show symptoms like red itchy skin, hot spots, diarrhea, or vomiting. That’s because mast cells, which are responsible for allergic reactions, are most concentrated on the skin and in the digestive tract of dogs (unlike humans—most of our mast cells are in our respiratory tract).

When allergens make contact with your dog's skin or enter their body through the respiratory system or digestive tract, they trigger these mast cells to produce histamine. This chemical causes blood vessels to expand and tissue to swell in an effort to drive immune cells to the site of the reaction while isolating the problem.

One method of controlling allergic reactions is to use a drug like Piriton, which targets histamine action.

What Is Piriton?

Piriton is a brand of antihistamine. The active ingredient, chlorpheniramine maleate, can also be found in other over-the-counter allergy products, including Aller-Chlor and Chlor-Trimeton. 

All these products are marketed for use in humans. However, many vets prescribe them off-label for use in dogs, cats, horses, and other domestic pets. 

How Does Piriton Work?

Like other antihistamine drugs, Piriton works by blocking cellular receptors for histamine. This helps prevent the inflammation and itching associated with doggy allergic reactions. It can also be used during targeted therapy to prevent acute allergic reactions and anaphylaxis caused by insect bites, vaccines, and anesthesia. 

For seasonal and ongoing allergy problems, Piriton must be given frequently, typically twice daily, every day. It has a short activity window and stops affecting the body within 24 hours of the last dose. 


Chlorpheniramine products are most effective in dogs when used to treat acute allergic reactions, such as those to insect bites, vaccinations, and other single-occurrence events. 

When used for long-term allergy problems, Piriton is much less effective. Like Benadryl, it tends to reduce symptoms but not erase them entirely. 

Also worth noting is that users can develop a tolerance to antihistamines. Typically this tolerance is mild and does not completely reduce the effectiveness of the drug. However, increased tolerance to one antihistamine translates to increased tolerance to all, regardless of the chemical makeup of the drug. In order to regain the original effect of the treatment, your dog will need to be taken off all antihistamines for three to 14 days each time tolerance begins to build. 

Risks and Side Effects

Piriton is well tolerated in most dogs, but it does come with some side effects that all owners should be aware of. These include:

  • Drowsiness
  • Diarrhea 
  • Dizziness 
  • Vomiting
  • Reduced appetite
  • Dry mouth
  • Straining during urination
  • Blurred vision
  • Confusion

Because chlorpheniramine is a first-generation antihistamine that crosses the blood-brain barrier, drowsiness is the most common side effect. Although rare, some dogs will react to Pririton with hyperactive behavior. 

Far less common than the above side effects are more serious effects, including seizures, breathing problems, muscle tremors, coordination problems, and coma. These are very rarely seen but have been reported when Piriton is used in dogs.

But by far the greatest downside for most dogs is simply that Piriton does not completely alleviate allergy symptoms. 

By targeting only the symptoms and not the cause, antihistamines like chlorpheniramine only provide partial relief. Worse still, they must be continued indefinitely in order to continue being effective. 


Piriton should not be given to dogs who are allergic to antihistamines or any of the ingredients in the drug. Due to potential interactions, this medication should also not be used in dogs who have been treated with monoamine oxidase inhibitors in the past 14 days.

You should also use caution when using Piriton in dogs with:

  • Closed-angle glaucoma
  • Enlarged prostate
  • High blood pressure
  • Hyperthyroidism
  • Heart disease
  • Gastrointestinal or bladder obstruction
  • Obstructive lung disease

When choosing an over-the-counter Piriton product for your pet, be sure chlorpheniramine maleate is the only active ingredient. Dogs can take Piriton in syrup, tablet, or drops form. No matter the form, be sure there are no added ingredients that could be toxic to dogs, including xylitol.

Natural Alternatives for Treating Allergies in Dogs

Piriton can be a great stopgap to help dogs find relief from allergies quickly. Unlike Apoquel, it is not habit-forming and rarely has serious side effects. And it gets to work quickly to help reduce itchy skin and digestive upset.

But this drug will do nothing to cure the cause of your dog’s allergies or help them find complete relief.

Luckily, there are some natural alternatives to Piriton that do more good for your dog. Some of these require more work on your part. But, by targeting the cause of your dog's problems and working with the body to fix it, they have the potential to cure your dog’s atopic dermatitis, hot spots, and frequent digestive upset to bring lasting relief.

Identify the Cause of Your Dog’s Allergy Symptoms

So many owners turn to Piriton because it is easy and inexpensive. But like most drugs, this antihistamine does nothing to stop the cause of your dog’s allergy symptoms. This means if you stop using it, your dog will be miserable once again.

Instead of masking symptoms, your goal should be to uncover where they're coming from.

The vast majority of dogs with atopic dermatitis suffer from environmental allergies. Dust mite allergies are the most common in this category, but fleas, mold, and grasses can also cause immune reactions. Those without environmental allergies are typically suffering from food allergies, which are becoming more and more common.

Identifying the cause of your dog’s discomfort can be tricky.

If your dog experiences problems only at certain times of the year or only in certain situations, an environmental allergy is most likely to blame. If their symptoms seem to get better after a good grooming, fleas may be the problem.

In these cases, do your best to isolate your dog from the suspected cause of the problem. This may mean using air purifiers inside, putting protective clothing on before going outside, or treating your dog for fleas. If these measures show an improvement, an environmental allergy is most likely.

However, if your dog's symptoms are constant regardless of changes to their lifestyle and the time of year, their diet may be to blame. 

Food allergies often cause digestive symptoms. But ongoing food allergies are just as likely to cause dermatitis and hot spots as environmental allergies are. If you think Fido’s diet may be to blame, jump to the next section to find out how to deal with food allergies and use a quality diet to help your pup recover. 

Address Their Diet

If your dog’s allergies are caused by something in their food, then addressing their diet is a must. But even if something in the environment is to blame, providing a quality, biologically appropriate diet can still improve their symptoms.

Food allergies are becoming more common in dogs. Chicken, beef, lamb, soy, corn, and wheat are all common culprits. These ingredients are also widely used in the dog food industry.

The first thing you should do if you suspect a food allergy is to switch to a diet with novel meat sources that doesn’t include the same grains or major plant ingredients that their current food does. 

Now, “novel” doesn't have to mean exotic. If your dog’s food contains only chicken and turkey now, you can try a beef recipe instead and vice versa. The important thing is to find a recipe that doesn't contain any of the major ingredients in your current food. 

If this doesn’t bring relief in 3 weeks or less, the culprit could still be lurking in the food. At this point, your best bet is a full elimination diet. 

Even if your dog is suffering from non-food allergen problems, it is worth it to take a close look at their diet. The skin uses about 30% of the protein your dog consumes. This means that if you're feeding a diet with too little protein, your dog’s skin will be the first thing to suffer. Essential fatty acids and many vitamins and minerals are also important for skin health.

Furthermore, many low-quality ingredients found in dog food can cause digestive problems that increase the risk of allergic reactivity. Synthetic additives, preservatives, processed grains and meats, and dyes all cause inflammation in the gut. And an inflamed gut is more prone to leaky gut syndrome, biome collapse, and other conditions that affect the health and reactivity of the immune system.

Raw diets are well known for supporting dog skin and coat health. If your dog is suffering from atopic dermatitis, hot spots, or other skin problems, consider switching to a raw or freshly prepared high-protein diet to help give them everything they need to recover quickly.

Reduce Environmental Exposure

A high-quality diet gives your dog the tools to build a healthy coat and resilient skin. But if they suffer from environmental allergies, they’ll still need more help.

If using an air purifier, avoiding going outside during high allergen periods, and our other tips from the first section don’t help, it may be time for an allergen test. 

Similar to human skin scratch tests, dog allergen scratch tests can be done at your veterinarian to see what exactly they are reacting to in their environment. Armed with this knowledge, you’ll have a better chance of reducing your dog’s exposure to the culprit and helping them find drug-free relief.

If you do go this route, make sure to forgo Piriton and other allergy medications for two weeks before the test. This will give the antihistamines plenty of time to clear your dog’s system in order to get unskewed results.

Probiotics and Enzymes

Along with a healthy diet, probiotics and enzymes are incredibly important for supporting immune health.

Seventy percent of the immune system is located in the gut in the form of symbiotic bacteria and vital chemical communication pathways. If your dog has been suffering from gut inflammation due to allergies or a poor diet, this important biome is likely to need rebuilding.

Using a quality supplement that includes potent soil-based probiotics and digestive enzymes will help repopulate the gut while increasing nutrient absorption and reducing leaky gut problems. Not only will this help dogs recover faster from allergy-related symptoms, but it can help reduce the formation of new allergies in the future. 

Allergies are a symptom of an immune system that is not working correctly. Supporting the gut is the first step to supporting the health of the immune system to reduce overactivity. 

Natural Remedies

In addition to probiotics and enzymes, there are many supplements out there that support gut, immune, and skin health. These have shown a high potential for helping dogs recover from atopic dermatitis and allergies.

Reishi mushrooms are one of the most potent medicinal mushroom species for immune and gut health. These functional mushrooms have immunomodulating compounds, which have been shown to normalize immune function. Reishi also contains beta-glucans, which encourage probiotic growth and reduce gut inflammation. 

Quercetin is a natural plant derivative that acts like an antihistamine in the body. Like Piriton, this won’t help address the cause of your dog’s allergies, but it can provide some relief while you work to identify food allergies or reduce environmental exposure to allergens. The effects aren’t as powerful as chemical antihistamines, but it comes with no side effects and benefits your dog's health, instead of harming it.

Coconut Oil is a great option to include in your pet's diet to increase their intake of skin-supporting fats. It also works as a wonderful topical home remedy for reducing itching and inflammation. Coconut oil has the added benefit of being a natural antibacterial, which can be very helpful when battling infected hot spots and skin that has been scratched raw. 

Choosing the Right Treatment for Your Dog

I’ve seen many dogs find relief using Piriton and other chlorpheniramine maleate products. But I have yet to see one who got off this medication and didn’t immediately start suffering from allergy symptoms again. 

As with most other allergy medications, Piriton only treats the symptoms, not the cause.

If you want your dog to truly find relief from itchy skin, hot spots, and frequent diarrhea, you need to address what is going on inside. That means determining what they are allergic to, working to remove that allergen from their food or environment, improving their diet, and utilizing gut-healthy supplements to reduce inflammation and immune reactivity.


CANINE ATOPIC DERMATITIS: SKIN ALLERGIES IN DOGS. (n.d.). Cabbagetown Pet Clinic. Retrieved May 5, 2023, from 

Chlorpheniramine Maleate | VCA Animal Hospitals. (n.d.). www.VCAHospitals.com. 

Dannenberg, T. B., & Feinberg, S. M. (1951). The development of tolerance to antihistamines. Journal of Allergy, 22(4), 330–339. 

Gao, Y., & Zhou, S. (2002). The Immunomodulating Effects of Ganoderma lucidum (Curt.: Fr.) P. Karst. (Ling Zhi, Reishi Mushroom) (Aphyllophoromycetideae)International Journal of Medicinal Mushrooms4(1), 11. 

Harvey, R. W. (1993). Food allergy and dietary intolerance in dogs: A report of 25 cases. Journal of Small Animal Practice34(4), 175–179. Verlinden, A., Hesta, M., Millet, S., & Janssens, G. (2006). 

Food Allergy in Dogs and Cats: A Review.Critical Reviews in Food Science and Nutrition46(3), 259–273. 

Sara Seitz

Sara Seitz worked in the pet industry for over a decade. In addition to being a certified dog trainer, Sara gained experience working as the general manager of a dog daycare and boarding facility, as the creator and manager of a pet sitting company, as a groomer, and as a dog behavior evaluator. She also has a bachelors in animal behavior from CSU. Currently, Sara works as a freelance writer specializing in blog, article and content writing.

2 thoughts on “Piriton for Dogs: Uses, Risks, and Natural Alternatives”

  1. Please let me know what is the “natural” alternative for flea and tick prevention since your article states that Nexgard and Frontline are poisons and are dangerous to my dog’s health??
    Are there products like Hwp and Bor-L-immune that I can give my dog to prevent fleas and ticks?
    Thank you

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