Dog being administered a liquid medication by owner

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If you have allergies, you know just how annoying they can be. From a runny nose and watery eyes to itchy skin and rashes that appear all over your body, depending on how severe your allergies are, they can significantly disrupt your daily routine.

However, it’s not only humans that are affected by allergies—our canine companions can experience allergic reactions as well, whether from environmental allergens like pollen and dust mites or certain food ingredients such as wheat and beef.

Thankfully, there are options available to alleviate allergy symptoms in dogs and provide relief. One such option is chlorpheniramine. In this blog post, we will explore the use of chlorpheniramine for dogs, its benefits, dosages, potential side effects, and alternatives. Keep reading to learn more.

What Is Chlorpheniramine?

Chlorpheniramine is an antihistamine used to treat allergic reactions in dogs

Chlorpheniramine is an antihistamine used to treat allergic reactions in humans. However, its application extends to veterinary medicine, where it is commonly prescribed off label for dogs.1

As an antihistamine, chlorpheniramine works by blocking the effects of histamine, a chemical released by the body during an allergic reaction. By blocking histamine, it helps to reduce allergy symptoms such as itching, sneezing, watery eyes, and nasal congestion.1 While chlorpheniramine for dogs is effective in managing certain allergic symptoms, it can also cause drowsiness, which is why it is sometimes prescribed as a mild sedative as well.2

Chlorpheniramine for dogs can be found in numerous formats, including tablets, capsules, and liquid suspensions. No matter what type your vet prescribes, you must follow their instructions closely to ensure your dog’s health and wellbeing.

Additionally, your vet may choose to prescribe chlorpheniramine maleate instead of chlorpheniramine. While these two medications have the same active ingredient, chlorpheniramine maleate for dogs features the addition of maleic acid to enhance its stability and solubility.

What Is Chlorpheniramine Used For In Dogs?

Chlorpheniramine for dogs is used to treat a range of allergies, including:

  • Environmental allergies: Environmental factors, such as pollen, dust mites, mold spores, and certain types of grass or plants, are common causes of allergic reactions in dogs.
  • Food allergies: Like humans, dogs can be allergic to food. From proteins like beef and chicken to common carbohydrates in commercial dog food such as corn and wheat, your dog can be allergic to a wide variety of food ingredients.
  • Insect allergies: Some dogs are highly sensitive to flea bites, while others can develop allergies to mosquitoes, ticks, and mites. If your dog gets stung by a bee, chlorpheniramine can help as well.
  • Contact allergies: Dogs can develop allergies when they come into contact with certain substances. This includes anything from cleaning and grooming products to fabrics.
  • Medication allergies: Medication allergies in dogs occur when their immune system overreacts to a specific drug. Always keep a close eye on your dog after administering a new medicine. For example, if you notice swelling on your dog's face or hives all over their body, speak with a vet as soon as possible.

Allergies in dogs can present a wide range of symptoms, ranging from mild to severe. While chlorpheniramine or chlorpheniramine maleate can help relieve certain symptoms in dogs, it's important to be careful about severe allergic reactions. If you notice your dog showing signs of anaphylactic shock, it is crucial to seek immediate veterinary assistance.

Chlorpheniramine Dosages

According to the Merck Veterinary Manual, dogs weighing less than 45 pounds should be given approximately 4 milligrams of chlorpheniramine every 8 hours. For dogs weighing over 45 pounds, the recommended dosage is 8 milligrams every 8 hours.3

However, these are just general guidelines. The exact chlorpheniramine dosage for dogs will depend on a variety of factors and differ from dog to dog. Let’s take a look at the factors that determine how much chlorpheniramine your dog should take.

  • Weight: Your dog’s weight has a huge influence on how much chlorpheniramine they should take. It plays a crucial role in how the medication is metabolized within their body. Generally, larger dogs require higher doses compared to smaller dogs. This is because a greater amount of medication is needed to achieve and sustain the desired effect in their system.
  • Age: The correct chlorpheniramine dosage for dogs also depends on age. For example, as dogs age, their metabolic rates often slow down and their organ function may decrease. As a result, older dogs generally require lower doses of chlorpheniramine compared to healthy adult dogs.
  • Health condition: If your dog has any pre-existing health conditions, they may require a modified amount of chlorpheniramine as well. In some cases, they may not be able to take the medication at all. For instance, dogs with heart disease, high blood pressure, urinary obstruction, and glaucoma should avoid taking chlorpheniramine.
  • Other medications: Certain drugs interact with chlorpheniramine, altering its absorption, distribution, and more. It is important to be aware of potential drug interactions and consult with a vet to ensure the safe and effective use of chlorpheniramine in combination with other medications.
  • Allergy severity: Additionally, the chlorpheniramine dosage for dogs can be determined by the severity of the symptoms. A dog experiencing minor symptoms may need a lower dose, whereas a dog with severe symptoms may require a higher dosage.

While it's important to understand the various factors that can influence how much chlorpheniramine your dog should take, never attempt to determine the dosage yourself. Always seek advice from a veterinarian and carefully adhere to their instructions to ensure the safety of your dog.

How Long Does Chlorpheniramine Take To Work?

Chlorpheniramine starts working quickly in dogs, usually within 1-2 hours

How long it takes for chlorpheniramine to work can vary depending on your dog’s weight, metabolism, and the severity of their symptoms. However, chlorpheniramine for dogs is generally a fast acting drug. You can expect it to take effect within 1 to 2 hours after administration.

Side Effects Of Chlorpheniramine

Side effects of chlorpheniramine

Like any medication, chlorpheniramine for dogs carries the potential for side effects. Some common chlorpheniramine for dogs side effects include:

  • Drowsiness: Chlorpheniramine can have a sedative effect on dogs, causing them to feel sleepy or lethargic.2
  • Dry mouth: When on chlorpheniramine, your dog may experience a decrease in saliva production, leading to a dry or sticky feeling in the mouth.2
  • Gastrointestinal issues: When it comes to taking chlorpheniramine, gastrointestinal issues like vomiting, diarrhea, and lack of appetite are relatively rare. If your dog is experiencing persistent diarrhea and vomiting, consult a vet immediately.
  • Urinary retention: Chlorpheniramine can affect bladder function in some dogs, leading to difficulty in urination or incomplete emptying of the bladder.2
  • Allergic reactions: Although chlorpheniramine for dogs is an antihistamine, it can also cause allergic reactions in some dogs. If you see any itching, hives, swelling, or difficulty breathing in your dog, take them to the vet as soon as possible.

Are There Alternatives To Chlorpheniramine For Dogs?

There are several alternatives to chlorpheniramine for treating allergies in dogs. Your vet will determine the best allergy medicine to use for your dog based on their current health condition, their medical history, the severity of their symptoms, and more.

Some alternatives to chlorpheniramine and chlorpheniramine maleate for dogs include:

  • Diphenhydramine (Benadryl)
  • Cetirizine (Zyrtec)
  • Loratadine (Claritin)

Chlorpheniramine For Dogs: FAQs

How much chlorpheniramine can I give my dog?

How much chlorpheniramine you can give to your dog will depend on their weight, age, health condition, how severe their allergy is, and whether they are taking any other medications. Always consult your vet when it comes to chlorpheniramine dosages for dogs. Follow their directions carefully to ensure your dog’s health and safety.

Can I give my dog chlorpheniramine that is meant for humans?

Chlorpheniramine is a medication that's used in both humans and dogs. However, the dosage for dogs is different than for humans, and human formulations might contain other ingredients that aren't safe for dogs. Always consult with a veterinarian before giving your dog any medication meant for humans.

Will chlorpheniramine make my dog sleepy?

Yes, chlorpheniramine will make your dog sleepy. Drowsiness and sleepiness are common side effects of chlorpheniramine for dogs. Because of this, veterinarians often prescribe chlorpheniramine not only for treating allergic reactions but also as a mild sedative.

Dog itching face with hind leg outdoors

Final Notes

Clorpheniramine is a valuable medication for managing allergies in dogs. As an antihistamine, it can effectively alleviate itching, sneezing, and other allergic reactions. While it can be found over the counter in many pharmacies, you should never give your dog chlorpheniramine without first consulting a veterinarian.

Veterinarians can assess your dog’s condition, determine the appropriate dosage of chlorpheniramine for them, and give you exact instructions on how to administer this medication to your beloved pup. By working together with a vet, you can ensure the safe and effective use of chlorpheniramine to improve your dog's condition.

If you have any more questions about chlorpheniramine for dogs, speak with a Dutch vet. Our vets can diagnose, prescribe, and provide you with all of the advice you need from the comfort of your own home. Get your dog’s medication delivered straight from our online pharmacy and skip the stress of an in-person vet visit. Try Dutch today.



  1. "Chlorpheniramine." MedlinePlus,

  2. Brooks, Wendy. "Chlorpheniramine Maleate (Chlor-Trimeton)." Veterinary Partner. 1 Jan. 2023,

  3. "Antihistamine Dosages." Merck Veterinary Manual.

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