Piriton for Dogs

Do not give Piriton or another human antihistamine to your dog unless your veterinary surgeon has confirmed the exact product, dose and frequency. The correct choice depends on the dog’s weight, health, symptoms, other medication and the active ingredients in the product.

What Is Piriton?

Piriton is a human antihistamine brand. Standard Piriton tablets contain the active ingredient chlorphenamine maleate, also called chlorpheniramine.

Chlorphenamine is a first-generation antihistamine. It works by blocking the effects of histamine, a substance involved in allergic reactions. It is described as a sedating antihistamine because drowsiness is a common effect.

Veterinary surgeons sometimes prescribe chlorphenamine for dogs to help manage certain allergic symptoms. Its use in dogs is generally off-label, meaning that it is a human medicine being used under veterinary direction.

Check the active ingredients, not just the brand name. Products with similar names can contain different medicines, and formulations may change. Some cold, flu or allergy products combine an antihistamine with a decongestant, painkiller, caffeine or another ingredient that may be dangerous to dogs.

Can I Give My Dog Piriton?

Only give it after speaking to your veterinary surgeon. Piriton may be suitable for some dogs and conditions, but it is not appropriate for every itch, rash, swelling or breathing problem.

Symptoms that appear to be an allergy can also be caused by fleas, mites, skin infection, ear disease, food reactions, pain, respiratory disease or another medical condition. An antihistamine may have little or no effect if the underlying cause is not histamine-related.

Antihistamines tend to work better for some types of mild allergic reaction than for long-standing canine skin disease. A dog with persistent itching needs investigation rather than repeated treatment with human medicine.

Severe Allergic Reactions

Contact a Vet Immediately

Do not rely on an antihistamine at home if your dog develops:

Difficulty breathing or noisy breathing.
Rapidly increasing swelling of the face, muzzle or throat.
Collapse, severe weakness or loss of consciousness.
Pale or blue gums.
Repeated vomiting or diarrhoea following a sting, medicine or food.
Sudden widespread hives accompanied by other symptoms.

A severe allergic reaction or anaphylaxis can progress rapidly and may require injections, oxygen, intravenous fluids and other emergency treatment. An oral antihistamine must not delay veterinary care.

Why There Is No Dosage Table on This Page

The previous version of this article gave a general dose according to body weight. This has been removed because an online table cannot safely account for:

The strength and formulation of the particular product.
The dog’s age, weight and general health.
The condition being treated.
Kidney, liver, heart, eye, urinary or respiratory disease.
Pregnancy or lactation.
Other medicines, supplements or flea treatments.
The frequency and duration intended by the veterinary surgeon.

If your vet recommends chlorphenamine, ask them to write down the exact product, tablet or liquid strength, amount per dose, frequency and duration. Do not calculate a dose from a human packet or another dog’s prescription.

Products to Avoid

Never assume that a product is safe merely because “Piriton”, “Benadryl”, “Piriteze” or “allergy relief” appears on the packaging. Brand formulations can differ between the UK and other countries.

Do not give combination products containing ingredients such as:

Pseudoephedrine, phenylephrine or another decongestant.
Paracetamol, ibuprofen or another human painkiller.
Caffeine or other stimulants.
Alcohol.
Xylitol, which may be present in some liquid or dissolvable products.

If there is any doubt, send your vet a clear photograph of the front of the packet and the complete ingredient list before giving it.

Possible Side Effects

Chlorphenamine can cause side effects even when given at a veterinary prescribed dose. These may include:

Sleepiness or lethargy.
Dry mouth and increased thirst.
Reduced appetite.
Vomiting or diarrhoea.
Difficulty or mild straining when urinating.
Occasionally, restlessness or unusual excitement instead of sedation.

Drowsiness should not automatically be dismissed as harmless. Contact your vet if it is pronounced, persists, interferes with walking or eating, or is accompanied by another symptom.

Stop giving the medicine and seek prompt veterinary advice if your dog develops:

Severe weakness or collapse.
Poor coordination or an inability to stand.
Muscle tremors or seizures.
Abnormal or difficult breathing.
A very rapid or irregular heartbeat.
Inability to pass urine.
Marked agitation, confusion or unusual behaviour.

Dogs Requiring Particular Caution

Chlorphenamine may be unsuitable or require additional caution in dogs with:

Glaucoma.
An enlarged prostate.
Difficulty urinating or a bladder obstruction.
An intestinal obstruction.
Heart disease or high blood pressure.
Overactive thyroid function.
Obstructive respiratory disease.
Liver or kidney disease.

Extra care may also be required for young puppies, elderly dogs, working dogs, pregnant bitches and nursing bitches.

Always tell your vet about every medicine, supplement, herbal product and flea or tick treatment your dog is receiving before starting an antihistamine.

Medicine Interactions

Chlorphenamine may interact with sedatives, some pain medicines, antidepressants, anticoagulants, anticonvulsants and monoamine oxidase inhibitors.

Amitraz, which has been used in some veterinary parasite treatments, may also interact with certain medicines. Do not combine products unless your vet has confirmed that it is safe.

Antihistamines can interfere with allergy skin testing. If your dog is being referred for testing, ask the specialist when the medicine should be stopped. Do not stop prescribed medication without checking first.

Piriton, Piriteze and Benadryl Are Not the Same

These are brand names rather than the names of a single medicine. Their active ingredients can be different:

Piriton normally contains chlorphenamine maleate.
Piriteze normally contains cetirizine hydrochloride.
Benadryl products sold in the UK may contain acrivastine, cetirizine or another ingredient. Products sold under the same brand in other countries may contain diphenhydramine.

The previous version of this article incorrectly stated that cetirizine was unsafe for pets. Veterinary surgeons do sometimes use cetirizine in dogs. However, this does not mean that every Piriteze or cetirizine-containing product is suitable, nor that an owner should choose the dose themselves.

Never substitute one brand or antihistamine for another using the same number of tablets. Different medicines have different strengths, doses, frequencies, side effects and interactions.

Other Antihistamines

Veterinary surgeons may use several antihistamines in dogs, including cetirizine, diphenhydramine, hydroxyzine or other medicines. The choice depends on the dog and the condition being treated.

There is no single “standard antihistamine dose” that can safely be applied to every product. A dose expressed in milligrams per kilogram for one active ingredient cannot be used for another.

Some antihistamines cause more sedation than others, and individual dogs respond differently. If one appropriately prescribed medicine does not help, discuss alternatives with your vet rather than increasing the dose or combining products.

Managing Long-Term Allergies

Piriton is not usually a complete answer to chronic itching. Effective management may require investigation and control of:

Fleas, mites or other parasites.
Bacterial or yeast skin infections.
Ear disease.
Environmental allergies such as pollen or house-dust mites.
Adverse reactions to food.
Contact irritation.
Another medical condition affecting the skin or coat.

Depending on the diagnosis, treatment might include parasite control, medicated shampoo, treatment of infection, an elimination diet, essential fatty acids or prescription allergy medication.

Omega-3 fatty acids may support skin health in some dogs, but EPA is a type of omega-3 fatty acid rather than an antihistamine. Supplements should be chosen and dosed with veterinary guidance because products vary in concentration and can cause digestive upset or interact with medication.

How Long Can a Dog Take It?

The appropriate duration depends upon the reason it was prescribed and whether it is helping. Some dogs may receive it briefly for a mild reaction, while others may be prescribed it for longer.

Do not continue indefinitely because symptoms return whenever it is stopped. Recurring or seasonal symptoms should be reviewed so that the underlying cause and the effectiveness of treatment can be assessed.

If a Dose Is Missed

Follow the instructions given by your veterinary practice. In general, do not give two doses together or give an extra dose to compensate without speaking to the vet.

Accidental Overdose

Contact your vet immediately if your dog receives too much chlorphenamine, eats the packet, or swallows an unknown quantity. Take the packaging with you and explain:

The product name and active ingredients.
The strength of each tablet or the liquid concentration.
Approximately how much may have been swallowed.
The time the incident occurred.
Your dog’s weight and any symptoms.

Do Not Wait for Symptoms

An overdose may cause severe drowsiness, agitation, abnormal heart rate, tremors, seizures, poor coordination, breathing abnormalities or coma. Contact your veterinary practice or its emergency service immediately.

Frequently Asked Questions

Is Piriton licensed for dogs?

Piriton is a human medicine. A veterinary surgeon may prescribe chlorphenamine for a dog under prescribing rules that allow the use of a human medicine when appropriate.

Can I give my dog the dose previously recommended for another dog?

No. Even dogs of a similar weight may have different conditions, medicines and risk factors. Obtain instructions for the individual dog.

Can I give Piriton every day?

Only when your veterinary surgeon has recommended the dose, frequency and duration. A dog needing daily treatment should also have the underlying cause of its symptoms assessed.

Will Piriton treat anaphylaxis?

It must not be relied upon as home treatment for a severe reaction. Anaphylaxis is an emergency and may require rapid injectable medication, oxygen, fluids and intensive veterinary support.

Is it safe to give Piriton before a vaccination?

Do not give it routinely before vaccination unless your vet has instructed you to do so. It is important that the veterinary team knows about any previous reaction and decides upon an appropriate plan.

Further information:

This page provides general information and is not a substitute for veterinary care. Do not give Piriton, Piriteze, Benadryl or another human medicine to your dog unless your veterinary surgeon has confirmed the exact product and dose.