Antihistamines for dogs: What’s safe, what’s not, and when to call the vet

It usually starts with something small. A swollen muzzle. Endless scratching. A dog sneezing like there’s pollen in the air. Before long, a worried pet parent is standing in front of the medicine cupboard, antihistamine in hand, asking the same question: Can I give this to my dog?

According to dotsure.co.za’s Vet of the Month, Dr Tiaan Venter from Langenhovenpark Animal Clinic, the answer is sometimes yes, but only with the right guidance. “Certain antihistamines can be safely used in dogs and cats,” he explains, “but only the correct ones, at the correct dose, and for the right type of allergy.” 

Showing your whiskered, wet-nosed and tail-wagging pet love responsibly means knowing when to call the vet instead.

Are human antihistamines safe for pets?

Not all human allergy medications are pet-friendly. Combination cold and flu products are particularly dangerous, especially those containing decongestants or painkillers.

The safest antihistamines for pets, under veterinary guidance, include:

• Cetirizine (Texa)
• Chlorpheniramine
• Mepyramine

Avoid anything containing paracetamol, pseudoephedrine or caffeine. “If those safer options aren’t available,” Dr Venter advises, “don’t give anything until you’ve spoken to a vet.”

What are antihistamines used for in pets?

Antihistamines work by blocking histamine, the chemical released during allergic reactions. They’re most effective for sudden, short-term reactions such as:

• Sneezing and runny noses
• Facial swelling from insect stings
• Mild itching, hives and seasonal allergies

They are far less helpful for chronic skin disease, tick bites or long-standing food allergies. “If the problem has been going on for a while, or keeps returning, a proper veterinary assessment is essential,” says Dr Venter. And while some antihistamines may cause mild drowsiness, they are not anxiety medication. “They should never be used to calm stressed or fearful pets,” he adds.

Allergy medication dosages for dogs and cats

When it comes to antihistamine dosage for pets, guessing can be dangerous. Cats are far more sensitive than dogs, and the dose depends on weight, concentration and active ingredient.

General guidance (remember to always confirm with your vet first):

• Small to medium dogs: half a tablet
• Large dogs: one tablet
• Adult cats: small, measured syrup doses

Children’s antihistamine syrups are sometimes used safely, but only after consulting a veterinarian.

What are the side effects of antihistamines in pets

Most pets tolerate antihistamines well, but possible side effects include vomiting, diarrhoea, drowsiness or agitation. Signs of overdose may include tremors, extreme lethargy or neurological symptoms.

“If symptoms are sudden, severe or getting worse, contact your vet immediately,” Dr Venter says.

When in doubt, call the vet

Showing your pet love isn’t about quick fixes; it’s about safe choices. Pause before you medicate. Ask before you dose. And ensure that every treatment starts with expert advice.

As dotsure.co.za’s Vet of the Month reminds pet parents: “Always contact your vet before giving human medication. That pause, that check, can make all the difference to your pet’s safety.”

Dotsure Limited (Registration number 2006/000723/06) is a licensed non-life insurer and authorised financial services provider (FSP39925). Voted South Africa’s Best Pet Insurance 2023-2025 by readers of The Star, Die Burger, Beeld, and City Press.