Antihistamines for Cats - Dosage, Types and Side Effects

María Besteiros
By María Besteiros, Expert veterinary assistant and canine/feline hairdresser.. August 7, 2023
Antihistamines for Cats - Dosage, Types and Side Effects

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Antihistamines for cats can be used to treat allergies by reducing the symptoms of a reaction. Despite the efficacy of these types of drugs for cats, we cannot give them to our cat without prior veterinary consultation. What may seem like an allergic reaction in the cat may be another issues with similar symptoms. There are also different types of antihistamines. Giving the wrong type to your cat can worsen their health rather than improve it.

At AnimalWised, we discover all you need to know about antihistamines for cats. We find out what types are available, what dosage is appropriate and what possible side effects may occur.

  1. What are cat antihistamines for cats?
  2. Dosage of antihistamines for cats
  3. Types of antihistamines for cats
  4. Contraindications of antihistamines for cats
  5. Side effects of antihistamines for cats
  6. Natural antihistamines for cats

What are cat antihistamines for cats?

Antihistamines are medications that are associated with the treatment of allergies. Although many of us associate our own allergies to cats, the same process can happen to felines. There are allergens in a cat's environment to which many are sensitive. These include the following:

  • Pollen
  • Dust
  • Spores
  • Food
  • Chemicals
  • Textiles
  • Insect bites

When a cat with a sensitivity to an allergen is exposed to one, they have a reaction which involves histamines. These are natural compounds in the cat's body which are used in various bodily functions, including in their immune response. When a cat with allergies suffers a reaction, the histamines respond in an exaggerated way. This is often in the case of issues such as atopic dermatitis in cats. This can lead to various symptoms, including:

  • Itchiness
  • Redness
  • Swelling
  • Hair loss
  • Vomiting
  • Respiratory problems
  • Excessive grooming
  • Runny nose
  • Wheezing

When the reaction is sufficiently severe, the cat can enter a state of anaphylactic shock. This is when the body starts to shut down due to their immune response, something which can be fatal in some cases.

Antihistamines work by reducing the activity of the histamines. They can slow or stop an allergic reaction by combatting their action. It is important to note that antihistamines for cats do not cure the allergy. They interfere with the reaction and reduce the symptoms, but the cat will still be sensitive to the allergen in the future.

Despite evidence supporting the effectiveness of antihistamines for cats, they are not the only treatment for allergies. There are currently other therapies for allergies which can be equally effective or more so, especially when used in combination with other drugs. There is also often a trial and error approach to antihistamines. Not all types of antihistamines for cats will work

Antihistamines can be beneficial in that they reduce the reliance on other drugs. These include corticosteroids such as prednisone for cats which can have certain side effects. Regardless of the allergy, we need to speak to a qualified veterinarian who can make an assessment. They will determine both whether antihistamines are a suitable treatment for your cat, as well as what type of antihistamine to prescribe. We should never give human antihistamine medication to our cat.

Antihistamines for Cats - Dosage, Types and Side Effects - What are cat antihistamines for cats?

Dosage of antihistamines for cats

The antihistamines for cats dosage must be determined by your veterinarian. As we have already asserted, you will need to seek veterinary guidance if your cat has an allergic reaction. This should be the case even if the reaction is relatively mild. Once the veterinarian has determined the allergen causing the reaction, they will decide which type of antihistamine for cats to administer. They will also determine the dosage and frequency.

Many brands of antihistamines are marketed and are available in different formats. The dose will depend on the specific antihistamine that the vet prescribes. To give an example, chlorpheniramine is prescribed at a rate of 2-4 mg twice a day orally. In contrast, 1-2 mg of hydroxyzine is recommended for each kg of weight, although it is also administered twice a day.

Types of antihistamines for cats

There are different brands of antihistamines that will vary in their strength. More important than the brans is the active ingredient of the antihistamine drug. Active ingredients can be either first or second generation. The most commonly used antihistamines for cats are the following:

  • Chlorphenamine: it is first generation and has the advantage that it produces few side effects. It is considered more effective in relieving itching if combined with omega 3 fatty acids. Trade names for this antihistamine include Piriton and Chlor-Tripolon

  • Cyproheptadine: it is related to adverse effects such as sedation, vomiting or behavioral changes.

  • Hydroxyzine: it has teratogenic capacity, i.e. it can cause malformations in pregnant cats if administered during pregnancy. It is first generation.

Other antihistamines include diphenhydramine or cetirizine. It should be borne in mind that some of those commonly used in human medicine can be toxic to cats.

Learn more about other drugs that are toxic to cats.

Contraindications of antihistamines for cats

As we have stated, we cannot give our cat antihistamines if the vet has not prescribed them. Not only could we cause adverse effects, but there are some situations in which the use of this type of drug is not indicated. For example:

  • Pregnant cats: care must be taken if we want to treat a pregnant cat, since these drugs can cause fetal malformations. Learn about health in pregnant cats with our article on whether a cat can be spayed during pregnancy.

  • Glaucoma or epilepsy: they are not recommended for cats that suffer from glaucoma or epilepsy.

  • Taking other medications: interactions with various drugs can also occur. This stresses the importance of communicating to the vet any treatment that we are administering to our cat before providing antihistamines.

If you don't know if your cat is pregnant or you don't know if the medication she is currently taking may be harmful if she takes antihistamines, consult your vet.

Antihistamines for Cats - Dosage, Types and Side Effects - Contraindications of antihistamines for cats

Side effects of antihistamines for cats

If you are prescribed the appropriate antihistamine and it is administered in the correct dosage, there are usually no adverse reactions. If side effects of antihistamines for cats do occur, they may include the following:

  • Sedation
  • Lack of coordination
  • Seizures
  • Mydriasis (i.e. pupil dilation)
  • Digestive problems

Digestive problems can include vomiting and diarrhea in the cat, but these only usually occur after prolonged exposure to the drug. Poisoning caused by the use of an inappropriate drug can trigger vomiting, seizures and bleeding. These cases require the immediate intervention of the veterinarian since they are considered a veterinary emergency.

Natural antihistamines for cats

Some products based on plant extracts promise an antihistamine effect. They often act as supplements, but any supplement should not be given without a vet's prescription. Natural antihistamines are not suitable for all cats. There must be verified scientific evidence that supports their effectiveness.

Conversely, it has been proven that the effect of antihistamines improves with the addition of fatty acids. When creating the diet for our cat, providing foods rich in omega-3 and omega-6- fatty acids can be a good option to include in their food. Remember that any supplement that is offered must be supervised by the veterinarian.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Antihistamines for Cats - Dosage, Types and Side Effects, we recommend you visit our Medicine category.

  • Saló, E. (2018). Feline skin hypersensitivity syndrome. Management and treatment. Canis et Felis, nº 154, 68-74.
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Antihistamines for Cats - Dosage, Types and Side Effects